Iverson_FM.qxd 1/17/05 6:03 PM Page i Apache Jakarta Commons Iverson_FM.qxd 1/17/05 6:03 PM Page ii BRUCE PERENS’ OPEN SOURCE SERIES http://www.phptr.com/perens ◆ Java™ Application Development on Linux® Carl Albing and Michael Schwarz ◆ C++ GUI Programming with Qt 3 Jasmin Blanchette and Mark Summerfield ◆ Managing Linux Systems with Webmin: System Administration and Module Development Jamie Cameron ◆ Understanding the Linux Virtual Memory Manager Mel Gorman ◆ PHP 5 Power Programming Andi Gutmans, Stig Bakken, and Derick Rethans ◆ Implementing CIFS: The Common Internet File System Christopher Hertel ◆ Open Source Security Tools: A Practical Guide to Security Applications Tony Howlett ◆ Embedded Software Development with eCos Anthony Massa ◆ Rapid Application Development with Mozilla Nigel McFarlane ◆ The Linux Development Platform: Configuring, Using, and Maintaining a Complete Programming Environment Rafeeq Ur Rehman and Christopher Paul ◆ Intrusion Detection with SNORT: Advanced IDS Techniques Using SNORT, Apache, MySQL, PHP, and ACID Rafeeq Ur Rehman ◆ The Official Samba-3 HOWTO and Reference Guide John H. Terpstra and Jelmer R. Vernooij, Editors ◆ Samba-3 by Example: Practical Exercises to Successful Deployment John H. Terpstra Iverson_FM.qxd 1/17/05 6:03 PM Page iii Apache Jakarta Commons Reusable Java™ Components Will Iverson Upper Saddle River, NJ • Boston • Indianapolis • San Francisco New York • Toronto • Montreal • London • Munich • Paris Madrid • Capetown • Sydney • Tokyo • Singapore • Mexico City Iverson_FM.qxd 1/17/05 6:03 PM Page iv Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein. The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which may include electronic versions and/or custom covers and content particular to your business, training goals, marketing focus, and branding interests. For more information, please contact: U. S. Corporate and Government Sales (800) 382-3419 corpsales@pearsontechgroup.com For sales outside the U. S., please contact: International Sales international@pearsoned.com Visit us on the Web: www.phptr.com Library of Congress Catalog Number: 2004115288 Copyright © 2005 Pearson Education, Inc. Pearson Education, Inc. Rights and Contracts Department One Lake Street Upper Saddle River, NJ 07458 ISBN 0-13-147830-3 Text printed in the United States on recycled paper at R.R. Donnelley & Sons Company in Crawfordsville, Indiana. First printing: February 2005 Iverson_FM.qxd 1/17/05 6:03 PM Page v For Cynthia. Iverson_FM.qxd 1/17/05 6:03 PM Page vi Iverson_FM.qxd 1/17/05 6:03 PM Page vii Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xiii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xvi About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xvii 1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Proper Versus Sandbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 License . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Obtaining and Installing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Configuration Under Eclipse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 From Here . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 2 FileUpload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Web and User Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 FileUpload Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Building an Application with FileUpload . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 FileUpload Application User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Sample FileUpload Application Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Application Presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Application Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Limitations and Security Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 3 HttpClient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 A Simple Cookie-Based Web Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Understanding HttpClient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Simple Swing Client . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Swing Client User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Swing Client Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 vii Iverson_FM.qxd 1/17/05 6:03 PM Page viii viii Contents 4 Net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Net Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 FTP Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 FTP Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 NNTP Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54 NNTP Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 5 Pool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 Interfaces and Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69 Thread Pool Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69 Object Factory Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74 Worker Thread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 6 DBCP (Database Connection Pool) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 Standalone DataSources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81 Client Connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81 Building the DataSource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 Legacy JDBC Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89 7 BeanUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 Understanding BeanUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 Using BeanUtils to Generate Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 Sample JavaBeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95 Presenting the Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95 FormBean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97 FormBeanUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 8 JXPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105 Setting Up the Example Object Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 Exploring the Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110 XPath and JXPath Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113 Basic XPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113 Complex XPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 JXPath Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 Supported Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117 9 Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 Trace Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 Using Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120 Logging Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125 Iverson_FM.qxd 1/17/05 6:03 PM Page ix Contents ix 10 Lang . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127 Base Lang Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127 ArrayUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 BitField . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 BooleanUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 CharRange, CharSet, and CharSetUtils . . . . . . . . . . . . . . . . . . . . . . . . . .129 ClassUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130 ObjectUtils and ObjectUtils.Null . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130 RandomStringUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130 SerializationUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 StringEscapeUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 StringUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132 SystemUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 Validate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 WordUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 Builder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135 Enum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 Exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 Math . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 11 Collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 Collections Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 Bag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 Bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142 BidiMap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144 Blocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145 Bounded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145 Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Circular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Closure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Collating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150 Comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150 Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151 Cursorable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151 Factory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152 Fast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152 Fifo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152 FixedSize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152 Flat3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Functor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Hash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Lazy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 Iverson_FM.qxd 1/17/05 6:03 PM Page x x Contents Linked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 LRU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 Multi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 NodeCaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 ObjectGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 Ordered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159 Predicate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Singleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 StaticBucket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162 Synchronized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162 Transformed/Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162 Typed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Unmodifiable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164 12 Codec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165 Character Encodings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 Base64 Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170 URL Form Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171 Hash Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173 Phonetic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176 13 CLI (Command-Line Interface) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 ClassPathTool Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 Building a Command-Line Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181 Running Command Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 Behind the Scenes with ClassPathTool . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191 14 Other Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Additional Commons Proper Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Betwixt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Daemon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 DbUtils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194 Digester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194 Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194 EL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194 IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194 Jelly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Iverson_FM.qxd 1/17/05 6:03 PM Page xi Contents xi Jexl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Latka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Launcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Math . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Modeler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Validator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Sandbox Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Cache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Clazz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Compress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Convert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Email . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 FeedParser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Functor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Id . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 JJar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Mapper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197 Messenger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Scaffold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 ThreadPool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 VFS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199 A Lang Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201 B Apache License, Version 2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331 Iverson_FM.qxd 1/17/05 6:03 PM Page xii Iverson_FM.qxd 1/17/05 6:03 PM Page xiii Preface I originally noticed the Jakarta Commons libraries while working with Apache Jakarta Tomcat. At some point, Tomcat started to include a suite of small libraries with commons in the name. They started to show up everywhere, in all sorts of other open source projects. At first, it was slightly off-putting—what exactly is commons-lang.jar, and why is this tiny library showing up in all of my software? Exploring the Jakarta Commons, I first found a broad suite of what I would characterize as "utility" code—things that often wound up in my soft- ware in packages named things like "util." Digging deeper, I found useful libraries to solve common problems, interesting algorithms, and more. In brief, by using the Jakarta Commons, I found I spent less time reinventing the wheel, and more time solving the problem at hand. Virtually every Java developer can take advantage of various Jakarta Commons components—from the utilities provided by the Collections and through the networking components afforded by the Lang packages, HttpClient and Net packages. These components underlie Apache Tomcat, Struts, and countless other projects, helping move forward both the Java industry and the Java platform. The first few chapters cover the more web-specific packages, including FileUpload, HttpClient, and the Net suite of protocol implementations. The Pool and DBCP packages are useful for a broader range of applications. BeanUtils and JXPath provide easier ways to work with objects. Logging, Lang, and Collections are a suite of tools applicable to almost every applica- tion. Codec provides a suite of specialized conversion routines, useful for data transfer, security, and (interestingly) phonetic analysis. Finally, the CLI pack- age provides support for building command-line applications. xiii Iverson_FM.qxd 1/17/05 6:03 PM Page xiv xiv Preface CHAPTER 1: OVERVIEW This chapter shows you where to download the various Commons components, and also how to install both the libraries and the documentation into Eclipse. CHAPTER 2: FILEUPLOAD This chapter shows how to easily add file upload capabilities to your web application. CHAPTER 3: HTTPCLIENT This chapter shows how to programmatically access HTTP resources. HttpClient provides many features, including cookie management and sup- port for a broad range of features. CHAPTER 4: NET This chapter shows how a wide variety of common Internet protocols can be accessed, including FTP, NNTP, and others. CHAPTER 5: POOL This chapter demonstrates the use of a suite of configurable object pools. CHAPTER 6: DBCP (DATABASE CONNECTION POOL) This chapter covers the DBCP package, useful for Swing applications and other situations in which a container is not managing database connectivity for you. CHAPTER 7: BEANUTILS This chapter shows how the information provided by JavaBeans-style objects can easily be accessed at run-time. CHAPTER 8: JXPATH As you build applications composed of complex graphs of objects, traversing those objects can become tedious. JXPath provides an easy mechanism for walking through these graphs. Iverson_FM.qxd 1/17/05 6:03 PM Page xv Preface xv CHAPTER 9: LOGGING Virtually every application can benefit from configurable logging—and the logging package is a good place to get started. CHAPTER 10: LANG Lang is one of the most useful packages, but one of the hardest to get started with. This chapter provides an overview of the Lang package, helping you get oriented. CHAPTER 11: COLLECTIONS This chapter covers powerful tools for working with collections—richer object relationships. CHAPTER 12: CODEC This chapter shows how to use a suite of specialized conversion routines useful for data transfer, security, and phonetic analysis. CHAPTER 13: CLI (COMMAND-LINE INTERFACE) Learn how to present consistent, useful command-line configuration and help information—with a bonus class path search tool. CHAPTER 14: OTHER PROJECTS This chapter provides a roadmap for a broad suite of other Commons projects— both the proper and sandbox. DOWNLOADING THE CODE The code presented in this book is available for download from http://www. cascadetg.com/commons/. Iverson_FM.qxd 1/17/05 6:03 PM Page xvi Acknowledgments Many, many thanks to Mark Taub for pulling this book together and being such a pleasure to work with. Thanks to my agent, Laura Lewin of StudioB, without whom this book would not exist. Thanks to the technical reviewers for taking the time to provide such excellent feedback, including Sylvain Gibassier, Mark Ferkingstad, and Lance Young. Any remaining mistakes are my own. On a personal note, thanks to friends and family for their support. In par- ticular, that includes adoor, alzo, dionysusdevotee, gaaneden, grandmoffdavid, hansandersen, jephly, jrpseudonym, merovingian, musae, p_fish, phoebek, pre- ciousjade, rogerothornhill, sajin, and zunger. And finally, thanks to Cynthia, Diane, and Mom. You are, quite simply, the best. xvi Iverson_FM.qxd 1/17/05 6:03 PM Page xvii About the Author Will Iverson has been working in the computer and information technology field professionally since 1990. His diverse background includes developing statistical applications to analyze data from the NASA Space Shuttle, product management for Apple Computer, and developer relations for Symantec’s VisualCafé. For nearly five years, Will ran an independent J2EE consult- ing company with a variety of clients including Sun, BEA, and Canal+ Technologies. He currently serves as the application development practice manager for SolutionsIQ. Will lives in Seattle, Washington. xvii Iverson_FM.qxd 1/17/05 6:03 PM Page xviii Iverson_ch01.qxd 1/17/05 2:34 PM Page 1 C H A P T E R 1 Overview The Apache Jakarta Commons project (http://jakarta.apache.org/commons/) is a collection of reusable Java software components. Each Commons project rep- resents a unit of functionality smaller than a full application—all of the vari- ous Commons projects are intended to help a Java developer build a useful application more quickly by leveraging existing components. Despite the range of functionality included in the various Commons projects, many devel- opers have not taken the time to understand or make use of these libraries, despite their inclusion in many of the most popular open source projects such as Tomcat and Hibernate. On the other hand, considering that the Commons project (as of this writing) consists of twenty-nine released proper components and twenty sandbox components, it’s easy to understand why some developers may find the project intimidating. Nonetheless, virtually every development project of any scope can benefit from the introduction of an appropriate Commons package. The Lang package alone contains a broad suite of simple utilities needed by almost every web application, such as a utility function for escaping a bit of HTML or SQL, or a quick class to make it easier to return a Date object formatted to a particular locale. The difficult thing about the Commons package is not the complexity associated with any particular project, but rather simply remembering what functionality is present. Therefore, the goal of this book is to provide an overview of the most useful Commons package for the broadest array of Java developers. Certain packages solve hard problems—for example, it’s easy to identify a need for the HttpClient package after hitting a wall with the built- in JDK HTTP connectivity suite. Implementing HTTP file upload capability from scratch is somewhat difficult, but the FileUpload package takes care of things nicely. Introspection is great, but BeanUtils is easier. And so on. Even the small bits add up quickly—it may seem easy to write your own utility methods, but those thirty minute one-offs can start to add up, especially considering the time needed to track down and fix minor bugs. Even more critically, other developers familiar with various Commons packages will imme- diately know where to find and how to use the utility routines in your project. 1 Iverson_ch01.qxd 1/17/05 2:34 PM Page 2 2 Overview Chapter 1 PROPER VERSUS SANDBOX The maintainers of the Commons project divide contributed code into two main areas, a "proper" suite and a "sandbox." The proper code is considered stable (and popular) enough to warrant a certain level of commitment—the interfaces are expected not to change without warning, and the code is consid- ered to have been tested well enough for production use. The sandbox, on the other hand, is open to anyone already accepted as a committer on another Jakarta project. The bulk of this book is devoted to the most popular and useful of the proper components—for more information on the sandbox components, see Chapter 14, "Other Projects." The proper components from the Commons package identified in Table 1-1 are covered in this book. Table 1-1 Covered Proper Components BeanUtils Chapter 7 CLI (Command Line Interface) Chapter 13 Codec Chapter 12 Collections Chapter 11 DBCP Chapter 6 FileUpload Chapter 2 HttpClient Chapter 3 JXPath Chapter 8 Lang Chapter 10 Logging Chapter 9 Net Pool Chapter 4 Chapter 5 Easy-to-use wrappers around the Java reflection and introspection APIs. Provides a simple API for working with command line arguments, options, option groups, mandatory options, and default help output. Contains phonetic encoders, Hex, Base64, and a URL encoder. Extends and augments the Java Collections Framework. Database connection pooling services. Based on the Pool component, described in Chapter 5, "Pool." Adds robust, high-performance, file upload capability to servlets and web applications. A framework for working with the client side of the HTTP protocol. Utilities for manipulating Java classes that con- form to the JavaBeans naming conventions using the XPath syntax. It also supports maps, DOM, and other object models. A very common set of utility classes, including routines for escaping text, enums, math, and time. A wrapper around a variety of logging API imple- mentations (including log4j and JDK logging). A collection of network utilities including Telnet, FTP, and NNTP clients. A generic object pooling interface, with classes for creating object pools and several general purpose pool implementations. Iverson_ch01.qxd 1/17/05 2:34 PM Page 3 Proper Versus Sandbox 3 The proper projects listed in Table 1-2 are not covered by this book. Some of these projects merely provide implementations of certain standards (e.g., the JSP Expression Language), are handled by other frameworks (e.g., DbUtils), or are too narrowly focused for coverage in this text. Table 1-2 Additional Proper Components Betwixt Chain Configuration Daemon DbUtils Digester Discovery EL IO Jelly Jexl Latka Launcher Math Modeler Primitives Validator Services for mapping JavaBeans to XML documents, and vice versa. Provides a "Chain of Responsibility" pattern implementation for organizing complex processing flows. Tools to assist in the reading of configuration/preferences files in various formats. An alternative invocation mechanism for Unix-daemon-like Java code. JDBC helper library that factors out mundane resource cleanup code for common database tasks. An XML-to-Java-object mapping utility commonly used for parsing XML configuration files. Provides tools for locating resources (including classes) by map- ping service/reference names to resource names using a variety of schemes. An interpreter for the Expression Language defined by the JavaServer Pages (TM) specification, version 2.0. Collection of I/O utilities. XML-based scripting and processing engine. An expression language that extends the Expression Language of the JSTL. An HTTP functional testing suite for automated QA, acceptance, and regression testing. Cross-platform Java application launcher. Eliminates the need for a batch or shell script to launch a Java application. Library of lightweight, self-contained mathematics and statistics components addressing the common practical problems not imme- diately available in the Java programming language. Provides mechanisms to create Model MBeans compatible with the Java Management Extensions (JMX) specification. Smaller, faster, and easier-to-work-with types supporting Java primitive types, with an emphasis on collections. Simple, extendable framework to define validation methods and validation rules in an XML file. Supports internationalization of rules and error messages. Iverson_ch01.qxd 1/17/05 2:34 PM Page 4 4 LICENSE Overview Chapter 1 The Apache Software Foundation, which maintains the Jakarta Commons project, is dedicated to providing open source software. The standard Apache license, which governs the Jakarta Commons, is considered a "business friendly" license—anyone can build software using the open source Commons code without needing to disclose modifications. For more information on the Apache Software Foundation license, licenses (such as the GPL), see including compatibility with other http://www.apache.org/licenses/. OBTAINING AND INSTALLING The Commons package (as well as the other Jakarta packages) is distributed in both binary and source forms. The binary releases can be found at: http://jakarta.apache.org/site/binindex.cgi The source code releases corresponding to the binary releases can be found at: http://jakarta.apache.org/site/sourceindex.cgi Finally, if you are interested in the latest (possibly unstable) release of Commons (or any other Jakarta software), instructions on CVS access are provided at: http://jakarta.apache.org/site/cvsindex.html Apache Jakarta The Apache Jakarta project (http://jakarta.apache.org) simply refers to the Java-related projects conducted under the Apache Software Founda- tion’s banner. Other popular Jakarta projects include the Tomcat web application server, the Cactus test framework, and the Velocity template engine. Certain projects, such as Struts and Ant, were originally part of the Jakarta project but have since "graduated" to exist as top-level Apache projects. Generally speaking, you are advised to download the binary release at a minimum. The binary releases of the Commons projects covered in this book typically include a single JAR file, a README.txt, a LICENSE.txt file, and a docs directory. The JAR file should be added to your class path. For example, you would copy the JAR file to your WEB-INF/lib directory for a web application. You may also want to download the source distribution if you want to con- tribute to, debug, or examine the Commons package. Iverson_ch01.qxd 1/17/05 2:34 PM Page 5 Configuration Under Eclipse 5 Directory Conventions On my Windows development system, I install downloaded libraries into a single directory, C:\devenv\. This represents my personal repository of downloaded libraries (and associated documentation, samples, etc.). My development source trees are stored in another directory, C:\devrep\, which is controlled by a version control system (CVS, soon to be converted to Subversion). As libraries are required by projects, I copy the .jar files from the C:\devenv\ directory into the appropriate location in C:\devrep\. Therefore, project-specific dependencies are resolved by relative paths, but upon occasion, interim development is done with references to the C:\devenv\ directory. I don’t use the C:\Documents and Settings\ directory because too many packages are confused by spaces in paths. On UNIX systems, I generally use ~\devrep\ and ~\devenv\. There’s nothing particularly magical about this strategy, but it does keep my tools and documentation nicely separated from my development tree. CONFIGURATION UNDER ECLIPSE Generally speaking, configuration of the various packages is development environment-specific. One of the more popular development environments is the free, open source Eclipse project (http://www.eclipse.org/). After down- loading and installing the environment, you can add various Jakarta Commons components to your project(s). Assuming you are starting with an existing Java project, right-click on the project name and select Properties, as shown in Figure 1-1. In the project properties, select the Java Build Path panel and then the Libraries tab, as shown in Figure 1-2. If you have copied the JAR file to your project (for example, in the WEB- INF/lib directory), you can click the Add JARs . . . button to add the JAR file to the build path. Alternatively, if you wish to store the JAR file external to the project, click Add External JARs. . . . Either way, you will be presented with a dialog to select the JAR file. Select the file and click OK to exit the project properties. The JAR is now configured on the Eclipse class path, ready for development. You may want to take advantage of Eclipse’s additional features. To com- plete installation, right-click on the entry for the JAR file and bring up the properties, as shown in Figure 1-3. Enter the path to the Javadoc for the distribution found in the docs/api directory of the binary release, as shown in Figure 1-4. Next, if you have downloaded the source for the package, you can click on Java Source Attachment in the JAR properties dialog and set the source location, Iverson_ch01.qxd 1/17/05 2:34 PM Page 6 Figure 1-1 Opening project properties. Figure 1-2 Java Build Path. 6 Iverson_ch01.qxd 1/17/05 2:34 PM Page 7 Figure 1-3 Opening JAR entry properties. Figure 1-4 Setting the Javadoc location. Iverson_ch01.qxd 1/17/05 2:34 PM Page 8 8 Overview Chapter 1 as shown in Figure 1-5. Note that the source is contained in the src/java directory. By setting the Javadoc location, Eclipse will display the Javadoc contents in addition to the type-ahead information, as shown in Fig- ure 1-6. Setting the source location will allow you to seamlessly bring up the source for the package when debugging. Figure 1-5 Setting the source location. Figure 1-6 Quick Javadoc information access. Iverson_ch01.qxd 1/17/05 2:34 PM Page 9 From Here 9 All of the Commons packages follow the same distribution structure and are downloaded from the same pages—the next step is to learn the actual packages. FROM HERE Each chapter except for the last provides an overview (and where appropriate, examples) for a major Commons proper package. The final chapter provides a bit more detail on the remaining packages, both proper and sandbox, including (where appropriate) a comment on the package status. Iverson_ch01.qxd 1/17/05 2:34 PM Page 10 Iverson_ch02.qxd 1/18/05 10:09 AM Page 11 C H A P T E R 2 FileUpload The first Jakarta Commons component we will examine is FileUpload, an aptly named library that makes it easy to add file upload capability to your web application. By using this library, a user can send a file to a web server by simply selecting a file in a web form and clicking "upload." Anyone who has used a popular web-based email client to send a file attachment has seen file upload functionality in action (for example, Yahoo! or Hotmail). In this chapter, we’ll look at how this library works and show how to use the key classes. WEB AND USER INTERFACES When working with a JSP or servlet, you may be accustomed to retriev- ing data from a javax.servlet.ServletRequest using the getParameter() and getParameterNames() methods. This works great for simple HTML-based forms, such as the one shown in Listing 2-1. The standard servlet method, request.getParameter("textfield"), is used to retrieve data submitted when the user clicks the Submit button. Listing 2-1 Simple Request JSP Request Example <%= request.getParameter("textfield") %>
The JSP page as rendered in a browser is shown in Figure 2-1. 11 Iverson_ch02.qxd 1/18/05 10:09 AM Page 12 12 FileUpload Chapter 2 Figure 2-1 Simple request starting page. As you can see in Figure 2-1, the initial page display shows "null" for the request.getParameter("textfield") call. Entering the words "Hello World!" into the text field and clicking the Submit button sends a page request back to the server (as specified by the action attribute). The server parses the request, and the form data is made available to the JSP. This can be seen in Figure 2-2. Figure 2-2 Simple request parsed response. This standard JSP/servlet mechanism works fine for normal HTML con- trols (check boxes, radio buttons, text fields, text areas, buttons, etc.). Unfortunately, it fails to handle file uploads using the HTML tag. Listing 2-2 Sample File Upload Form
The code shown in Listing 2-2 is an example of an HTML file upload form. Notice the addition of the enctype="multipart/form-data" attribute to the form, as well as the tag. The enctype attribute governs how the browser should package and send the data back to the server (for more infor- mation on this, read RFC 1867 at http://www.ietf.org/rfc/rfc1867.txt). Figure 2-3 shows the HTML tag as rendered by Internet Explorer. Iverson_ch02.qxd 1/18/05 10:09 AM Page 13 FileUpload Design 13 Figure 2-3 FileUpload user interface. The Jakarta Commons FileUpload component provides support for the file upload capability of a typical web browser, letting you go beyond the limi- tations of the parameter parsing of the standard servlet system. FileUpload will parse the data returned by the multipart/form-data form and file input type as sent by your browser. FILEUPLOAD DESIGN FileUpload has two main points of interest to a user: the class org.apache. commons.fileupload.DiskFileUpload, which parses the incoming data, and the interface org.apache.commons.fileupload.FileItem, returned when the file upload data has successfully been parsed. The class hierarchy for DiskFileUpload is shown in Figure 2-4. To use DiskFileUpload, the application needs to set a temporary path on disk to spool file data and the size threshold. It’s easy to envision applications that might require several megabytes to be uploaded at a time, and by using the DiskFileUpload class with appropriate thresholds, the application will try not to overload the server. Be Aware of Performance Impacts The Java servlet model uses a single thread per request. If your applica- tion server is set to provide a maximum of fifty threads for handling incoming requests, fifty file uploads can starve the server for additional requests. You may want to consider isolating the file upload capability of your application from the thread pool for the rest of the application. For example, in Tomcat, you may want to define a second HTTP connector on a different port with another thread pool for handling file upload requests. This is application server-specific functionality, but be aware that file uploads are typically much longer-lived, resource-intensive operations than simply handling an ordinary page request. More seriously, a series of file uploads could easily be used to launch a denial-of-service attack. In a production environment, make sure that only authenticated users are allowed to initiate a file upload. 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It returns a List of FileItem objects, shown in more detail in Figure 2-5. «reference» Serializable «interface» FileItem delete () : Void get () : Byte[] getContentType() : String getFieldName() : String getInputStream () : InputString getName () : String getOutputStream () : OutputStream getSize () : LongInteger getString () : String getString (encoding:String) : String isFormField() : Boolean isInMemory() : Boolean setFieldName(name:String) : Void setFormField(state:Boolean) : Void write (file:File) : Void DefaultFileItem collapsed collapsed + + Figure 2-5 FileItem class. The bulk of the methods of the FileItem interface are fairly self-explanatory. The most significant thing to be aware of is that using get() will load the entire file into memory at once, whereas getInputStream() allows for buffering and other stream operations. Iverson_ch02.qxd 1/18/05 10:09 AM Page 16 16 FileUpload Chapter 2 BUILDING AN APPLICATION WITH FILEUPLOAD Now that we understand the basic design of the FileUpload component, let’s look at a simple application that makes use of FileUpload. As shown in Fig- ure 2-6, the JSP pages provide a user interface, and a set of Java helper classes are used to configure and invoke the FileUpload component. JSP User Interface Helper Java Classes Apache FileUpload Figure 2-6 FileUpload application overview. By centralizing the access to the FileUpload component in the helper classes, the configuration of the FileUpload component can be changed with- out updating the JSP pages. For example, you may want to configure the max- imum permissible file size, the kind of files that may be updated, or the buffering of uploaded data to memory or disk. FileUpload Application User Interface A user visiting the file upload web application is first prompted to add a file, as shown in Figure 2-7. Figure 2-7 Add File request. Clicking the link takes the user to a file upload form, as shown in Fig- ure 2-8. Clicking the Browse . . . button (a standard browser user interface widget) prompts the user to select a file on disk. Here, we’ve selected a file on the C:\ drive. Clicking Upload sends the selected file to the server. The file is uploaded, and then the user is returned to the file list, as shown in Figure 2-9. You’ll notice that the user can click on the file name to download the file again via HTTP, the file size is reported in bytes, and the MIME type (as reported by the browser) is listed. Additionally, the Location Iverson_ch02.qxd 1/18/05 10:09 AM Page 17 Sample FileUpload Application Code 17 Figure 2-8 File Upload form. Figure 2-9 Uploaded File list. link points to the file location on the server’s file system. Finally, clicking Delete will remove the file from disk. The user interface is quite straightforward, and in the next section we’ll look at the code required to build it. SAMPLE FILEUPLOAD APPLICATION CODE The code for the application consists of the following files: ☞ index.jsp—The main interface, as shown in Figure 2-7 and 2-8. Lists the files that have been posted. ☞ post.jsp—The file upload form, as shown in Figure 2-9. These two JSP pages in turn make use of two Java classes. ☞ Files.java—Acts as the manager of uploaded files. Keeps track of informa- tion about the files that have been uploaded, such as the location on disk. ☞ FileUploadHelper.java—This application class wraps the Commons FileUpload class, making it easier to use in JSP pages. This provides a central location to keep track of the FileUpload configuration. Iverson_ch02.qxd 1/18/05 10:09 AM Page 18 18 FileUpload Chapter 2 Application Presentation The index.jsp page is shown in Listing 2-3. You’ll notice a small bit of logic at the top to handle a file deletion. Otherwise, the bulk of the file deals with loop- ing over the file list and other formatting. Note that when your JSP page issues a sendRedirect(), as shown in the JSP scriptlet header, a return is used to avoid additional processing of logic on the page. This simple technique is used to avoid a variety of potential problems. Listing 2-3 File Listing JSP <%@ page language="java" import="com.cascadetg.ch02.*" %> <% java.util.Hashtable myFilesHashtable = Files.getFiles(); java.util.Enumeration myFilesEnumeration = myFilesHashtable.elements(); if(request.getParameter("delete") != null) { Files.deleteFile(application, request.getParameter("file")); response.sendRedirect("index.jsp"); return; } %> File Upload Example <% if (myFilesHashtable.size() == 0) { %> No files posted. <% } else { %> <% while(myFilesEnumeration.hasMoreElements()) { %> org.apache.commons.fileupload.FileItem myFile = (org.apache.commons.fileupload.FileItem) myFilesEnumeration.nextElement(); response.encodeURL(FileUploadHelper.getFileName(myFile.getName())) + "&delete=true" %>">Delete <% } /* End of file display iteration */ %>
File Size Type Location  
<%= FileUploadHelper.getFileName(myFile.getName()) %> <%=myFile.getSize()%> <%= myFile.getContentType()%> ">Local File
<% } /* End of file list display */ %>

Add File

The form used to upload a file to the server is shown in Listing 2-4. You’ll notice that there is only a small bit of code—the heavy lifting is handled by the FileUploadHelper class. Listing 2-4 File Post JSP <%@ page language="java" import="java.sql.*" %><% com.cascadetg.ch02.FileUploadHelper myFileHelper = new com.cascadetg.ch02.FileUploadHelper(); if(myFileHelper.doFilePost(request, application)) { response.sendRedirect("index.jsp"); return; } %> ch02 : File Post
File
Comment
 

Return To File List

Iverson_ch02.qxd 1/18/05 10:09 AM Page 20 20 FileUpload Chapter 2 Application Logic The FileUploadHelper (diagrammed in Figure 2-10) handles the request, stor- ing the uploaded files in one Hashtable and the form parameters in another. This application doesn’t actually make use of the form parameters, but it would be easy to add access methods to get to the data if it were needed. For example, you might want to allow a user to set a comment for a file on the same page as a form upload. FileUploadHelper fileUpload:DiskFileUpload= new DiskFileUpload() files: Hashtable = new Hashtable() parameters: Hashtable= new Hashtable() doFilePros (request:HttpServletRequest, context:ServletContext) : Boolean getFileName(in:String) : String Figure 2-10 FileUploadHelper class diagram. Listing 2-5 shows the declaration and three main bits of information tracked when a file is uploaded. First, it’s possible that more than one file may be uploaded in a single POST (hence the files hash table). Second, the parameters hash table is used to track any additional non-file form data sent by the browser. In this example, we don’t actually make use of the form parameters, but it would be easy to add access methods to get to the data if it were needed. For example, you might want to allow a user to send a comment for a file on the same page as a form upload. Finally, the third instance variable, fileUpload, contains a reference to the DiskFileUpload class. This object is used to actually perform the parsing. Listing 2-5 FileUploadHelper (part 1) package com.cascadetg.ch02; import java.io.File; import java.util.*; import org.apache.commons.fileupload.*; import javax.servlet.http.*; /** This class is used to handle an uploaded file. */ public class FileUploadHelper { /** Used to store the uploaded files just uploaded. Note that * these are tracked by the Files class. */ Hashtable files = new Hashtable(); /** Used to track the additional parameters sent along with the * file. For example, you might send a textarea form element (continues) Iverson_ch02.qxd 1/18/05 10:09 AM Page 21 Sample FileUpload Application Code 21 Listing 2-5 (continued ) * along with a comment describing the file. */ Hashtable parameters = new Hashtable(); /** The org.apache.commons.fileupload.DiskFileUpload class used * to actually handle the upload processing. */ DiskFileUpload fileUpload = new DiskFileUpload(); Listing 2-6 shows that the doFilePost() method handles the file upload as sent by the JSP. First, some basic tests are performed to ensure that a form upload has actually been posted. Next, the fileUpload object is configured—the maxi- mum file size, the maximum size to store in memory before spooling to disk, and the temporary location to spool the file are set. The value shown for the repository path is based on the current web application context—depending on the operating system and application server you are using, you may wish to set this to some other value. The remainder of the class simply parses the incoming request and then loops through the returned response for additional information. Obviously, for a large file, the fileUpload.parseRequest(request) call may block for some time while the file is uploaded. You should consider this carefully when designing your web application. You may notice that a simple utility method (getFileName) is provided for stripping the path information from the incoming form. As of this writing, Microsoft Internet Explorer 6 returns the full path of the uploaded file sent by the user (for example, C:\myfolder\myfile.txt), whereas Mozilla-based browsers (such as Firefox) only return the actual name of the file (myfile.txt). Similarly, some operating systems return the path with \ characters for the path separator, and others use the / character. For these and a multitude of other reasons, you’ll want to test your web application thoroughly to ensure that it is compatible with a wide range of browsers. Listing 2-6 FileUploadHelper (part 2) /** Returns true if it's a file post, false if not. If it's * false, we know that we should use the standard servlet * methods for getting the parameters. */ public boolean doFilePost(HttpServletRequest request, javax.servlet.ServletContext context) { if (request.getContentType() == null) return false; if (!request.getContentType().startsWith("multipart/form-data")) { // Not a multi-part/form-data post, which means we // should use standard servlet methods for getting // parameters return false; } (continues) Iverson_ch02.qxd 1/18/05 10:09 AM Page 22 22 FileUpload Chapter 2 Listing 2-6 (continued ) // Maximum files size in bytes before a FileUploadException // will be thrown fileUpload.setSizeMax(10 * Files.MB); // maximum size that will be stored in memory before we // start spooling to disk fileUpload.setSizeThreshold(4 * Files.KB); // Set the location to spool temporary files fileUpload.setRepositoryPath(Files.getTempPath(context)); try { // Use the fileUpload object (DiskFileUpload) to parse // the request. List fileItems = fileUpload.parseRequest(request); // Loop through the uploaded files and parameters Iterator i = fileItems.iterator(); while (i.hasNext()) { FileItem file = (FileItem)i.next(); // MS IE reports the full path as the name, but // we're only interested in the actual file name. String fileName = file.getName(); fileName = getFileName(fileName); if (file.isFormField()) { // If it's a form field, we'll want to make it // available as a parameter. parameters.put( file.getFieldName(), file.getString()); } else { // If it's not a form field, we'll assume it's // a file and add it both to this upload,to the // list of posted files, and write the file to // disk. files.put(fileName, file); Files.getFiles().put(fileName, file); File upload = new File( Files.getUploadPath(context) + fileName); file.write(upload); } } } catch (Exception e) { e.printStackTrace(); } return true; } (continues) Iverson_ch02.qxd 1/18/05 10:09 AM Page 23 Sample FileUpload Application Code 23 Listing 2-6 (continued ) // A utility method to strip the path information away from the // submitted file. We assume that the / and the \ characters // are the only ones returned. public static String getFileName(String in) { String result = in; if (result != null) { if (result.indexOf("\\") > 0) result = result.substring( result.lastIndexOf("\\") + 1, result.length()); if (result.indexOf("/") > 0) result = result.substring( result.lastIndexOf("/") + 1, result.length()); } return result; } } The final code, as modeled in Figure 2-11, acts as an in-memory record of the uploaded files. You’ll notice that a few attempts are made at security—for example, the application blocks certain extensions from being uploaded to the server in an attempt to avoid spreading viruses. Files KB: Integer = 1024 MB: Integer - 1024 * 1024 directorySep : String = System.getProperty("file.separator") uploadFiles: Hashtable = new Hashtable() deleteFile(context:ServletContext, file:String) : Void getBasePath(context:ServletContext) : String getDownloadPath(request:HttpServletRequest) : String getFiles() : Hashtable getTempPath(context:ServletContext): String getUploadPath(context:ServletContext): String isBlockedFile(fileName:String) : Boolean Figure 2-11 Files class diagram. The source for the application’s in-memory record, shown in Listing 2-7, deals with a number of platform-specific functions in addition to tracking the files themselves. For example, depending on your operating system, you may Iverson_ch02.qxd 1/18/05 10:09 AM Page 24 24 FileUpload Chapter 2 want to deny certain file names. A list of inappropriate file extensions for Microsoft Windows is shown—you may want to add more if you are using another operating system. Similarly, instead of the relatively permissive model shown, you may want to default to denying all files and only allow cer- tain file types to be posted (for example, your application may only allow .zip archives, both to avoid potential security issues associated with other file types and to save space on the server). You may notice that the temporary spool location (getBasePath) is inside the WEB-INF folder. This location is only used for random, unique temporary spool files—a user cannot overwrite a file in the WEB-INF directory in this fashion, but you may want to set this to an appropriate platform-specific temporary file location for increased security. Uploaded files are placed in an upload directory. After a file has been uploaded, anyone can download the file by merely pointing his or her web browser to the proper location. If you want to protect the files, you may want to place them instead in a WEB-INF\upload directory, in a completely different directory outside of the web application, or even in a database. From there, a user who wanted to download one of these files would have to go through the authentication scheme you’ve chosen, and then your application would stream the data via a servlet as needed. Keep in mind that in that case, your web appli- cation is taking on a role (streaming static file content) that is otherwise han- dled by a different system (for example, Apache httpd or Tomcat’s dedicated static resource handler). You will want to carefully consider the implications in terms of performance before putting this into production. Listing 2-7 File Management package com.cascadetg.ch02; import java.io.File; import java.util.*; import org.apache.commons.fileupload.*; import javax.servlet.http.HttpServletRequest; /** This static class is used to manage the files posted to the * server. */ public class Files { public static Hashtable getFiles() { return uploadedFiles; } private static Hashtable uploadedFiles = new Hashtable(); /** * List of blocked file extensions taken from the MS security * note posted at... * http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q235309 */ static public final String[] blockedFileExtensions = { ".ade", ".adp", ".bas", ".bat", ".chm", ".cmd", ".com", ".cpl", ".crt", ".exe", ".hlp", ".hta", ".inf", ".ins", (continues) Iverson_ch02.qxd 1/18/05 10:09 AM Page 25 Sample FileUpload Application Code 25 Listing 2-7 (continued ) ".isp", ".js", ".jse", ".lnk", ".mda", ".mdb", ".mde", ".mdz", ".msc", ".msi", ".msp", ".mst", ".pcd", ".pif", ".reg", ".scr", ".sct", ".shs", ".url", ".vb", ".vbe", ".vbs", ".wsc", ".wsf", ".wsh", // Also, don't allow people to upload code! "jsp", "php", "asp", "class", "java" }; /** Useful constants */ public static int KB = 1024; public static int MB = 1024 * 1024; /** Needed when working with files on disks */ public static String directorySep = System.getProperty("file.separator"); /** * Used to determine if a file should not be uploaded based on * file extension. */ public boolean isBlockedFile(String fileName) { String lowerCaseName = fileName.toLowerCase(); for (int i = 0; i < blockedFileExtensions.length; i++) { if (lowerCaseName.endsWith(blockedFileExtensions[i])) return true; } return false; } /** * The base path corresponds to the base directory of the * application context's WEB-INF directory. This means that * this directory is NOT visible to the end user. */ public static String getBasePath( javax.servlet.ServletContext context) { return context.getRealPath("/") + "WEB-INF" + directorySep; } /** * The temporary directory used to store files while they are * being uploaded. */ public static String getTempPath( javax.servlet.ServletContext context) { return getBasePath(context) + "tmp" + directorySep; } /** * Gets the upload directory - used to indicate the local file * system storage area. */ public static String getUploadPath( javax.servlet.ServletContext context) { return getBasePath(context) + ".." + directorySep + "ch02" + directorySep + "upload" + directorySep; } /** * The path to the upload directory - used to retrieve a file * from the server. */ public static String getDownloadPath(HttpServletRequest request) { return request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + "/" + "ch02/upload/"; } (continues) Iverson_ch02.qxd 1/18/05 10:09 AM Page 26 26 FileUpload Chapter 2 Listing 2-7 (continued ) /** Deletes the uploaded file. */ public static void deleteFile( javax.servlet.ServletContext context, String file) { FileItem myFile = (FileItem)uploadedFiles.get(file); if (myFile == null) return; // Marks temporary file for deletion. myFile.delete(); // Deletes the uploaded file File diskFile = new File(getUploadPath(context) + myFile.getName()); if (diskFile.exists()) diskFile.delete(); // Removes from the in-memory hash. uploadedFiles.remove(file); } } LIMITATIONS AND SECURITY ISSUES Before continuing, it’s worth taking a moment to consider some of the limita- tions of the sample code as shown. Most of these limitations are easily solv- able, but it’s worth considering both the inherent limitations and the security implications of uploading file data to the server. ☞ The sample code shown previously stores the list of uploaded files in memory only (using a Hashtable)—if you’re doing this "for real," you’ll want to store data about the uploaded files with some sort of persistent mechanism (for example, using a relational database). ☞ The sample code shown previously stores files using the file name as the "unique identifier." This is a pretty simplistic mechanism, and it is prone to conflict if two files are uploaded with the same name. Again, the use of a database and a synthetic primary key may be your best bet. ☞ This is not an inherently transactionally safe operation—it’s easy to think of situations that might "confuse" the application, such as uploading a new file with the same name as a file that is currently being downloaded. ☞ In general, error handling is limited to dumping an exception to the con- sole. For a production application, you will want to handle all possible error scenarios as gracefully as possible. ☞ Some attempt is made to prohibit uploading potentially "dangerous" file types to the server. It may be more appropriate to store files in a fashion that doesn’t preserve the original filenames on a file system—either by hashing the filenames or perhaps by storing the files in a database. Iverson_ch02.qxd 1/18/05 10:09 AM Page 27 Summary 27 Similarly, you may only want to allow users to upload a certain set of file types and prohibit all others. ☞ It’s terribly easy to choke your entire web application with a denial-of- service attack by simply initiating a large number of file uploads. Therefore, you will likely only want to allow users to initiate a file upload after they have authenticated. You may want to adopt a further strategy, such as a flag to only allow an authenticated user to upload a single file at a time, or you might want to use a pool to manage file uploads. ☞ No provision is made to protect file downloads. If a file is uploaded to a directory, anyone who has the URL can download it. If you want to pro- tect the uploaded file in some fashion (for example, requiring a login), you’ll need to add a mechanism to "hide" the file and only send it to approved users. It’s a truism that when considering the security of an application, you can’t "trust" anything that comes from the client browser. This is doubly true when considering file uploads. When adding file upload capability, make sure you’ve fully considered the security implications. SUMMARY In this chapter, an application was shown demonstrating the use of the FileUpload component to add file uploads to a web application. In the next chapter, this will be flipped around to look at a library intended to help a client application download data from a web server. Project Ideas Use FileUpload in conjunction with the FTP component of the Net pack- age (described in Chapter 4, "Net") to allow users to post files to an FTP server via a browser. Create a web version of a file system browser. Add security and mecha- nisms for implementing common file system commands such as move, copy, rename, and delete. Use FileUpload to add file upload capability. Use the Codec package (described in Chapter 12, "Codec") to encode files stored on disk uploaded via FileUpload. Write a program to examine the different file upload characteristics as provided by as many different browsers as possible (e.g., Mozilla Netscape, Mozilla Firefox, different versions of Internet Explorer for Mac OS and Windows, Lynx, Mac OS X Safari, Opera . . .). Add performance metrics to compare different browsers. Does the servlet container (e.g., Apache Jakarta Tomcat) affect the performance? Iverson_ch02.qxd 1/18/05 10:09 AM Page 28 Iverson_ch03.qxd 1/17/05 2:38 PM Page 29 C H A P T E R 3 HttpClient It goes without saying that there is a staggering amount of data available on the Internet—specifically, available via the World Wide Web (HTTP). One of the wonderful things about the JDK is the built-in ability to access resources via HTTP—specifically, the java.net.HttpURLConnection class shows that sim- ple HTTP resources can easily be downloaded by Java applications. Unfortunately, the built-in HTTP connectivity in the JDK suffers from some significant limitations (for a partial feature set comparison, see http://www.nogoop.com/product_16.html#compare). Fortunately, these limita- tions are overcome when using the Commons HttpClient. A full list of features supported by HttpClient (including links to the relevant RFCs) can be found at http://jakarta.apache.org/commons/httpclient/features.html, but some of the most interesting features include: ☞ Automatic Cookie Management—Allowing access to web resources that require web form authentication and session tracking via cookies. ☞ Multipart form POST for file upload—See Chapter 2, "FileUpload," for more information on multipart form posts and file upload. ☞ True request/response streams—The 1.4.2 implementation of Java copies data into a byte array before sending and receiving data, whereas HttpClient passes the streams directly to the application. ☞ Built-in support for transparently handling redirects. Glancing at Figure 3-1, which shows the non-Exception classes just in the org.apache.commons.httpclient package, you might think that the HttpClient package is complex and difficult to use. While exercising the full range of capa- bility may be complex, we’ll look at how we can use the HttpClient classes to easily deal with cookies and posting forms. The biggest difference between HttpClient and the default JDK HTTP connectivity is the use of classes to implement each of the various HTTP requests. These classes are then passed to a persistent HTTP client object to execute. Listing 3-1 shows a simple GET request. The response to a particular method invocation is bound to the method object, not the client. 29 Iverson_ch03.qxd 1/17/05 2:38 PM Page 30 d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c . s e s s a l c t n e i l C p t t H n i a M 1 - 3 e r u g F i Iverson_ch03.qxd 1/17/05 2:38 PM Page 31 A Simple Cookie-Based Web Site 31 Listing 3-1 Simple GET Request HttpClient client = new HttpClient(); HttpMethod method = new GetMethod("http://www.cascadetg.com/"); client.executeMethod(method); System.out.println(method.getStatusCode()); System.out.println(method.getResponseBodyAsString()); method.releaseConnection(); Redirects One of the nuisances of dealing with the default JDK HTTP connectivity is the lack of support for server redirects. The server uses a redirect to indicate to a client that the requested page is no longer available and that the client should load an alternative page. Unlike the JDK implemen- tation, this redirect is transparently followed by HttpClient (i.e., your application receives the content from the redirected URL). You can option- ally configure the handling of redirects on a per-request basis with the HttpMethod.setFollowRedirects() method. You also the HttpMethod.getPath() method after the execute() to obtain the path that was actually finally read. can use If you only want to follow a certain number of redirects before failing, you should turn setFollowRedirects() to false and detect redirect status responses manually. A SIMPLE COOKIE-BASED WEB SITE Let’s look at a very simple web page, as shown in Figure 3-2. Figure 3-2 Simple web page. You’ll notice a counter is displayed—the server uses a cookie to track the number of times the page has been viewed. Each time the page is refreshed, the counter is increased. For this functionality to work, we need to support cookies on the client—otherwise, the counter won’t update. Iverson_ch03.qxd 1/17/05 2:38 PM Page 32 32 HttpClient Chapter 3 The other thing you’ll notice is the form, which enables a client that does support cookies to reset the counter. Let’s look at the JSP code for this simple web page in Listing 3-2. Listing 3-2 Simple Cookie JSP <%@ page contentType="text/html; charset=utf-8" language="java" %> <% Cookie myCookie; String counter = "0"; if(request.getParameter("Submit") != null) { myCookie = new Cookie("counter", null); response.addCookie(myCookie); } else { Cookie[] cookies = request.getCookies(); if(cookies != null) for(int i = 0; i < cookies.length; i++) { if(cookies[i].getName().compareTo("counter") == 0) counter = cookies[i].getValue(); } if(counter == null) counter = "0"; if(counter.compareTo("null") == 0) counter = "0"; counter = (Integer.parseInt(counter) + 1) + ""; session.setAttribute("counter", counter); myCookie = new Cookie("counter", counter); response.addCookie(myCookie); } %> Cookie Test Page

Counter: <%= counter %>

Reload Page

You’ll notice the use of cookie management facilities built into the standard JSP/servlet functionality. It’s a shame that similar functionality isn’t built into the standard Java SDK for accessing resources via HTTP—instead, we must turn to the Jakarta Commons HttpClient component for assistance. UNDERSTANDING HTTPCLIENT The basic object when working with HttpClient is, of course, HttpClient, as shown in Figure 3-3. This object represents a complete HTTP client, keeping track of state (e.g., cookies and authentication management), and it includes support for things like connection pooling and persistent connections. Iverson_ch03.qxd 1/17/05 2:38 PM Page 33 Understanding HttpClient 33 HttpClient LOG: Log = LogFactory.getLog(HttpClient.class) connetionTimeout : Integer = 0 hostConfiguration : HostConfiguration httpConnectionManager : HttpConnectionManager httpConnectionTimeout : LongIngeger = 0 state : HttpState strictMode : Boolean = false timeoutInMillisecond : Integer = 0 HttpClient () HttpClient(httpConnectionManage:HttpConnectionManager) _@id118657Initializer _@id36305Initializer endSession () : Void executeMethod (hostConfiguration:HostConfiguration, method:HttpMethod): Integer executeMethod (hostConfiguration:HostConfiguration, method:HttpMethod, state:HttpState) executeMethod (method:HttpMethod) : Integer getHost () : String getHostConfiguration() : HostConfiguration getHttpConnectionManage () : HttpConnectionManage getPort () : Integer getState () : HttpState isStrictMode () : Boolean setConnectionTimeout(newTimeoutInMillisecondsInteger) : Void setHostConfiguration(hostConfiguration:HostConfiguration) : Void setHttpConnectionFactoryTimeout(timeout:LongInteger) : Void setHttpConnectionManage (httpConnectionManage:HttpConnectionManage) : Void setState (state:HttpState) : Void setStrictMode(strictMode:Boolean) : Void setTimeout(newTimeoutInMillisecondsInteger) : Void startSession (host:String, port:Integer) : Void startSession (host:String, port:Integer, creds:Credentials) : Void startSession (host:String, port:Integer, creds:Credentials, https:Boolean) : Void startSession (host:String, port:Integer, https:Boolean) : Void startSession (host:String, port:Integer, proxyhost:String, proxyport:Integer) : Void startSession (host:String, port:Integer, proxyhost:String, proxyport:Integer, secure:Boolean) : Void startSession (url:URL) : Void startSession (url:URL) : Void startSession (url:URL, creds:Credentials) : Void Figure 3-3 HttpClient class. Iverson_ch03.qxd 1/17/05 2:38 PM Page 34 34 HttpClient Chapter 3 To actually make a connection, create a "method" object, corresponding to the type of request desired (for example, GET, POST, PUT, OPTIONS, HEAD, etc.). The most common methods are GET (a simple URI retrieval, e.g., "http://www.cascadetg.com/") and POST (sending form data back to a URI). For more information on the other methods, you may want to consult the RFC for HTTP 1.1 at http://www.ietf.org/rfc/rfc2616.txt. The hierarchy of meth- ods can be found in Figure 3-4. The main methods of interest for HttpMethod and HttpUrlMethod are shown in Figure 3-5. You may want to inquire about the current status of the client, for exam- ple to determine the current state of the cookies that have been set. To do this, you use the HttpClient.getState() method. This returns an HttpState object, as shown in Figure 3-6. So, to recap, you’ll use an HttpClient object as a single representation of a client, you’ll create an HttpMethod to make a connection, and you’ll inspect the HttpState object to get data about the current client state. Content Type Given a particular URI, you may be curious about the type of content being downloaded. The content type is typically expressed in a notation known as MIME (see http://www.iana.org/assignments/media-types/). For example, text/plain indicates an ordinary text file, image/png indicates a PNG file, and application/msword indicates a Microsoft Word document. Depending on the type of content downloaded, you may want to take dif- ferent action for dealing with the data. Generally speaking, you have three options for determining the MIME type of a bit of content: the information supplied by the server, the file name, and guessing based on the actual bytes of the file content. Ideally, the server should be configured to return the MIME of the data sent as a header, in which case you would use the HttpMethod.getRequestHeader("Content-Type") method to obtain the content MIME type. Unfortunately, the server may be set to send the incorrect type. In this case, you can use the static method java.net.URLConnection .guessContentTypeFromName(String fname) to attempt to guess the file type based on the file name and extension. Finally, if that doesn’t work, you may want try java.net.URLConnection.guessContentTypeFromStream (InputStream is). None of these methods is guaranteed to be correct— depending on your application, you may want to default to a particular method and document this behavior in your user documentation. to Iverson_ch03.qxd 1/17/05 2:38 PM Page 35 Understanding HttpClient 35 Figure 3-4 HTTP methods relationship diagram. Iverson_ch03.qxd 1/17/05 2:38 PM Page 36 addRequestHeader(header:Header) : Void addRequestHeader(headerName:String, headerValue:String) : Void addRequestFooter(footer:Header) : Void execute (state:HttpState,connection:HttpConnection) : Integer getDoAuthentication () : Boolean getFollowRedirects () : Boolean getHostConfiguration () : HostConfiguration getName () : String getPath () : String getQueryString () : String getRequestHeader(headerName:String) : Header getRequestHeaders () : Header[] getResponseBody () : Byte[] getResponseBodyAsStream () : InputStream getResponseBodyAsString () : String getResponseFooter(footerName:String) : Header getResponseFooters () : Header[] getResponseHeader(headerName:String) : Header getResponseHeaders () : Header[] getStatusCode () : Integer getStatusLine () : StatusLine getStatusText () : String getURL () : URL hasBeenUsed () : Boolean isStrictMode () : Boolean recycle () : Void releaseConnection () : Void removeRequestHeader (headerName:String) : Void setDoAuthentication (doAuthentication:Boolean) : Void setFollowRedirects ( followRedirects:Boolean) : Void setPath(path:String) : Void setQueryString (params:NameValuePair[]) : Void setQueryString (queryString:String) : Void setRequestHeader (header:Header) : Void setRequestHeader (headerName:String, headerValue:String) : Void setStrictMode (strictMode:Boolean) : Void validate () : Boolean co llapsed co llapsed getURL() : String setURL (url:String) : Void Figure 3-5 HttpMethod interface. 36 Iverson_ch03.qxd 1/17/05 2:38 PM Page 37 Simple Swing Client 37 Figure 3-6 HttpState. SIMPLE SWING CLIENT Now that you understand how HttpClient is put together, let’s consider a sim- ple Swing client designed to talk specifically to the JSP shown in Listing 3-2. Before diving into the code, let’s look at how our Swing client works. Swing Client User Interface Figure 3-7 shows the initial user interface. Notice the text field at the top, allowing the user to specify a URL, and the two buttons. Iverson_ch03.qxd 1/17/05 2:38 PM Page 38 38 HttpClient Chapter 3 Figure 3-7 Initial Swing client view. Figure 3-8 Viewing cookies. Clicking the Load button sends a GET request to the specified URL. Fig- ure 3-8 shows the client after clicking the Load button three times—you’ll notice that the counter cookie, displayed at the top of the page (along with the session cookie), is now set to three. The main text area shows the content of the retrieved page, and the bottom bar displays the response code as sent by the server. Clicking the Clear button sends a form POST back to the server, as shown in Figure 3-9. The JSP being posted to (see Listing 3-2) is set up to clear the cookies when that form data is received. Swing Client Code Now let’s look at the actual code behind this Swing application, starting with Listing 3-3. The main method of interest is the testCookies() method. Depend- ing on the URL retrieved, you may also get cookie data. Iverson_ch03.qxd 1/17/05 2:38 PM Page 39 Simple Swing Client 39 Figure 3-9 Clearing cookies. Listing 3-3 Swing Client GET package com.cascadetg.ch03; import org.apache.commons.httpclient.*; import org.apache.commons.httpclient.methods.*; import java.awt.*; public class SwingClient extends javax.swing.JFrame { HttpClient client = new HttpClient(); public SwingClient() { initComponents(); } /** Gets a page via http and displays the cookies and the page */ public void testCookies() { // Sometimes the Internet is slow. this.setCursor(Cursor.WAIT_CURSOR); // We set up a GET request using the URL entered in the URL // textfield. HttpMethod method = new GetMethod(this.urlTextField.getText()); try { client.executeMethod(method); } catch (Exception e) { e.printStackTrace(); } // Set the response label to the returned value. this.responseCodeLabel.setText(method.getStatusCode() + ""); // Now, we start building the text to display. StringBuffer response = new StringBuffer(); (continues) Iverson_ch03.qxd 1/17/05 2:38 PM Page 40 40 HttpClient Chapter 3 Listing 3-3 (continued ) // First, we loop through the currently set cookies. Cookie[] cookies = client.getState().getCookies(); for (int i = 0; i < cookies.length; i++) { response.append(cookies[i].getName()); response.append("="); response.append(cookies[i].getValue()); response.append("\n"); } response.append("================================"); response.append("\n"); // Next, we get the response as a String response.append(method.getResponseBodyAsString()); // Finally, we display the response. this.responseText.setText(response.toString()); // Some clean-up. method.releaseConnection(); method.recycle(); // Set the cursor back this.setCursor(Cursor.DEFAULT_CURSOR); } Listing 3-4 shows the POST request, in this case hard-coded to map to the JSP page shown in Listing 3-2. Note that in this case, a simple POST is used—if you want to upload files, for example, you would use the MultipartPostMethod class in- stead of PostMethod. Also notice the use of the releaseConnection method—while not strictly necessary in this trivial app, you need to clean up in this fashion for better performance, and if you later want to switch to a multithreaded client (using the MultiThreadedHttpConnectionManager), cleaning up this way is necessary. Listing 3-4 Swing Client POST /** * We submit a POST request. In this example, we are submitting * a form where we know that a single Submit is the sole * contents of the form. In a "real" browser, you would have * parsed the sent HTML, displayed the user interface, and then * built the response from the displayed user elements. */ public void testPost() { // Sometimes, the Internet is slow. this.setCursor(Cursor.WAIT_CURSOR); try { // Set up a POST retrival HttpMethod method = new PostMethod(this.urlTextField.getText()); // Let's add the form value ((PostMethod)method).addParameter( (continues) Iverson_ch03.qxd 1/17/05 2:38 PM Page 41 Simple Swing Client 41 Listing 3-4 (continued ) "Submit", "Clear Cookies!"); // Now, we send the POST client.executeMethod(method); // Here's where we handle the response. Because we've // hard-coded this to work with our form, we know that // we're trying to clear the cookies. StringBuffer response = new StringBuffer(); response.append("Using form submit to clear cookies!"); response.append("\n"); response.append("================================"); response.append("\n"); // Here we get the returned response to display response.append(method.getResponseBodyAsString()); // Now we display it in the Swing UI this.responseText.setText(response.toString()); this.responseCodeLabel.setText( method.getStatusCode() + ""); } catch (Exception e) { e.printStackTrace(); } finally } { // Clean up our connection method.releaseConnection(); } this.setCursor(Cursor.DEFAULT_CURSOR); In the interest of completeness, the final portion of the code, shown in Listing 3-5, creates the Swing graphical user interface for the application. Threading and Timeouts This application executes the HTTP calls on the same thread as the Swing user interface. In practice, this means that a request to a slow or unavailable server can lead to an apparent application freeze (the user interface won’t update until the response has been returned). This means that for a "real" application, you will want to run your HTTP requests on a different thread than your Swing user interface. Similarly, you may want to open multiple threads to download different resources simultaneously. To do this, create your HttpClient with a multi-threaded connection manager: HttpClient client = new HttpClient(new MultiThreadedHttpConnectionManager()). Make sure that you use a finally block to wrap method.releaseConnection() to ensure that connections are properly recycled. Similarly, you will want to ensure that no individual connection sits idle, waiting for data from a server for too long. Simply use the HttpClient.setTimeout() method to specify the timeout in milliseconds. If you are building a production Swing application and are concerned about threading, check out SwingWorker: http://java.sun.com/products/jfc/tsc/articles/threads/update.html Iverson_ch03.qxd 1/17/05 2:38 PM Page 42 42 HttpClient Chapter 3 Listing 3-5 Simple Swing Client Code // Swing user interface variables declaration private javax.swing.JPanel buttonPanel; private javax.swing.JButton clearButton; private javax.swing.JButton goButton; private javax.swing.JLabel responseCodeLabel; private javax.swing.JPanel responseCodePanel; private javax.swing.JTextArea responseText; private javax.swing.JScrollPane responseTextPanel; private javax.swing.JPanel topPanel; private javax.swing.JTextField urlTextField; /** Initializes the Swing user interface. */ private void initComponents() { topPanel = new javax.swing.JPanel(); urlTextField = new javax.swing.JTextField(); buttonPanel = new javax.swing.JPanel(); goButton = new javax.swing.JButton(); clearButton = new javax.swing.JButton(); responseCodePanel = new javax.swing.JPanel(); responseCodeLabel = new javax.swing.JLabel(); responseTextPanel = new javax.swing.JScrollPane(); responseText = new javax.swing.JTextArea(); setTitle("SwingHTTPClient"); addWindowListener(new java.awt.event.WindowAdapter() { public void windowClosing( java.awt.event.WindowEvent evt) { } }); System.exit(0); topPanel.setLayout(new java.awt.BorderLayout()); urlTextField.setFont(new java.awt.Font("SansSerif", 1, 12)); urlTextField.setText( "http://localhost:8080/ch03/index.jsp"); topPanel.add(urlTextField, java.awt.BorderLayout.CENTER); buttonPanel.setLayout(new java.awt.BorderLayout()); goButton.setText("Load"); goButton .addActionListener(new java.awt.event.ActionListener() { public void actionPerformed( java.awt.event.ActionEvent evt) { } testCookies(); }); buttonPanel.add(goButton, java.awt.BorderLayout.WEST); clearButton.setText("Clear"); (continues) Iverson_ch03.qxd 1/17/05 2:38 PM Page 43 Summary 43 Listing 3-5 (continued ) clearButton .addActionListener(new java.awt.event.ActionListener() { public void actionPerformed( java.awt.event.ActionEvent evt) { } }); testPost(); buttonPanel.add(clearButton, java.awt.BorderLayout.EAST); topPanel.add(buttonPanel, java.awt.BorderLayout.EAST); getContentPane().add(topPanel, java.awt.BorderLayout.NORTH); responseCodePanel.setLayout(new java.awt.BorderLayout()); responseCodePanel.setBorder( new javax.swing.border.EtchedBorder()); responseCodePanel.setEnabled(false); responseCodeLabel.setText("Result"); responseCodePanel.add(responseCodeLabel, java.awt.BorderLayout.CENTER); getContentPane().add(responseCodePanel, java.awt.BorderLayout.SOUTH); responseTextPanel.setViewportView(responseText); getContentPane().add(responseTextPanel, java.awt.BorderLayout.CENTER); java.awt.Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize(); setBounds((screenSize.width - 400) / 2, (screenSize.height - 300) / 2, 400, 300); } public static void main(String args[]) { new SwingClient().show(); } } SUMMARY In this chapter, you’ve seen how a complex library can easily be used to handle something beyond the abilities of the default JDK. Working with cookies and handling both GET and POST requests are fundamental building blocks for the Internet. In the next chapter, you’ll look at components for dealing with other fundamental building blocks, such as FTP and NNTP. Iverson_ch03.qxd 1/17/05 2:38 PM Page 44 44 HttpClient Chapter 3 Project Ideas Write a proxy server, recording the data sent between the browser and a web server. Save this data and then see if you can repeat the interactions with HttpClient. Would this be useful for testing web applications? Most application developers work with GET and POST requests. Find a web server that supports the full range of HTTP requests and write an interactive application that supports the full range of HTTP request types. Add some logic to parse the returned HTTP. Can you find URLs in the HTTP? If you can find the URLs, is it worth trying to preload the underly- ing data, perhaps by running HttpClient in the background as a proxy server? Alternatively, is this a reasonable approach to building a spider application to crawl through a website? Iverson_ch04.qxd 1/17/05 2:39 PM Page 45 C H A P T E R 4 Net In the previous chapters, you’ve looked extensively at HTTP and HTML—two of the most fundamental standards behind the Internet. The major protocols behind email (POP3, SMTP, IMAP, MIME) are all supported by JavaMail (http://java.sun.com/products/javamail/). This leaves a tremendous number of other protocols, however. The Jakarta Commons Net package covers a huge number of the other standard Internet protocols, including Finger, Whois, TFTP, Telnet, FTP, NNTP, and some miscellaneous protocols such as Time, Echo, and BSD R. POP3 and SMTP are also supported, but JavaMail (http://java.sun.com/ products/javamail/) provides a more mainstream, higher-level wrapper for these protocols. ☞ Finger—http://www.faqs.org/rfcs/rfc742.html. A simple status inquiry. ☞ Whois—http://www.faqs.org/rfcs/rfc954.html. A lookup mechanism, allowing users to find information about registered users (in particular, such as Network Solutions, used by domain name registries, http://www.networksolutions.com/en_US/whois/index.jhtml). ☞ TFTP—http://www.faqs.org/rfcs/rfc991.html. A very simple file trans- fer protocol with no access control. Sometimes found on local networks as part of a network boot process. ☞ Telnet—http://www.faqs.org/rfcs/rfc854.html. A generic two-way proto- col, most commonly used for remote shell access, but also acting as the underlying infrastructure of other standards (such as FTP). ☞ FTP—http://www.faqs.org/rfcs/rfc959.html. A popular, more sophisti- cated file transfer protocol than TFTP. ☞ NNTP—http://www.faqs.org/rfcs/rfc977.html. Network News Transfer Protocol, most popularly known as the underlying protocol behind USENET. If you aren’t familiar with USENET, check the Google inter- face available at http://www.google.com/grphp. 45 Iverson_ch04.qxd 1/17/05 2:39 PM Page 46 46 Net Chapter 4 ☞ BSD "R" Commands—A set of commands intended to provide remote services without a login (including rexec, rcmd/rshell, and rlogin). For more information (including a discussion of the security implications), see http://www.busan.edu/~nic/networking/firewall/ch08_04.htm. Warning: It should be noted that virtually no security is built into any of these protocols. Those that offer username/password authentication transfer login information in the clear. If you are interested in secure alternatives, you may want to consider a virtual private network or the use of an SSH tunneling system such as OpenSSH (http://www.openssh.org/). This chapter will first look at the overall architecture of the Net package and then delve more deeply into the FTP and NNTP clients. NET OVERVIEW Probably the most fundamental thing to understand about the Net package is that it is intended to provide protocol access, not a higher-level abstraction. In practice, this means that objects tend to have methods that are highly sequen- tial and generally more "procedural" in flavor. The following list indicates the packages of the Net package—you’ll notice that they mostly correspond directly to the supported protocol list mentioned previously. ☞ examples ☞ org.apache.commons.net ☞ org.apache.commons.net.bsd ☞ org.apache.commons.net.ftp ☞ org.apache.commons.net.ftp.parser ☞ org.apache.commons.net.io ☞ org.apache.commons.net.nntp ☞ org.apache.commons.net.pop3 ☞ org.apache.commons.net.smtp ☞ org.apache.commons.net.telnet ☞ org.apache.commons.net.tftp ☞ org.apache.commons.net.util Let’s look at one of these packages in a bit more depth. Figure 4-1 shows the ftp package classes. The key classes are FTPClient (a representation of the connec- tion with methods to perform standard FTP connectivity), and FTPFile (which wraps directory and file list information). Most of the FTPClient methods are quite literal, issuing commands across a single connection—for example, methods such as FTPClient.deleteFile(java.lang.String pathname) or FTPClient makeDirectory(java.lang.String pathname). Iverson_ch04.qxd 1/17/05 2:39 PM Page 47 Net Overview 47 «reference» TelnetClient «reference» «interface» Serializable «interface» «interface» FTPFileEntryParser FTPFileListParser collapsed collapsed FTP collapsed collapsed FTPClient collapsed collapsed FTPFileParseImpl DefaultFTPListParser FTPFile collapsed collapsed collapsed collapsed FTPReply FTPCommand collapsed collapsed collapsed collapsed FTPFileList FTPFileIterator collapsed collapsed collapsed collapsed collapsed «reference» IOException FTPConnectionClosedException collapsed Figure 4-1 FTP class diagram. Origins of Commons Net According to the Apache Jakarta Commons Net web site, the package was originally developed as a commercial suite, NetComponents: "NetComponents was originally a commercial product, but after ORO dissolved, it was continued to be made available for those who found it useful. However, no updates have been made since version 1.3.8, released in 1998. Now that certain contract obligations have expired, it is possible to make the source code freely available under the Apache Software License." It’s fortunate that even though ORO dissolved, the time and energy to convert this to an Apache Jakarta project was made. It should be noted that the comment to the effect that "no changes have been made" is incor- rect, as browsing the reports of the project shows that it is still under active development as of this writing. The usage of the Net package classes is fairly straight forward: a connec- tion is established, the initial reply code is read, information is sent back and forth, and then the connection is disconnected. Iverson_ch04.qxd 1/17/05 2:39 PM Page 48 48 Net Chapter 4 Warning: It is important to remember that checking for the initial reply code is not optional. Issuing other commands won’t work until you retrieve that first reply code. In this chapter, you’ll look at two simple web applications that make use of this library, one to access an FTP server, the other to access an NNTP server. Neither implements a full "client," but they do demonstrate two approaches to accessing the server. The first, the FTP "gateway," opens a con- nection to the FTP server, reads the resulting data, and then closes the connection. The second, the NNTP "gateway," maintains a single connection to the NNTP server and attempts to cache data retrieved (a reasonable assump- tion, given the mostly read-and-post nature of NNTP). FTP FUNCTIONALITY Our FTP example shows how you can display the contents of remote FTP server via a web page, as shown in Figure 4-2. FTP is a relatively old, cumber- some protocol, not as well known as the standard HTTP/HTML used by web browsers. Most users wind up downloading and installing custom FTP clients to access FTP resources, although most modern browsers have some cumber- some FTP access capability built-in. Figure 4-2 Viewing FTP directory contents. The page is fairly simple—when the page is first visited, the default login directory is shown. When a link is clicked, the dir parameter is passed back to Iverson_ch04.qxd 1/17/05 2:39 PM Page 49 FTP Implementation 49 the page, and the contents of the new directory are displayed. This allows a user to easily browse the contents of an FTP server. The links at the top of the page allow a user to quickly return "up" the directory’s path. FTP IMPLEMENTATION The code for the user interface is shown in Listing 4-1. You’ll notice that the FTPConnection class does the bulk of the work, including much of the format- ting of the returned listings. Listing 4-1 FTP Web JSP User Interface <%@ page contentType="text/html; charset=iso-8859-1" language="java" import="com.cascadetg.ch04.*" %><% String directory = request.getParameter("dir"); FTPConnection myConnection = new FTPConnection(); if(directory != null) myConnection.setWorkingDirectory(directory); myConnection.connect(); %> FTP Listing : /<%= myConnection.getWorkingDirectory() %>

Directory : <%= myConnection.getHTMLFormattedWorkingDirectory("ftp.jsp") %>

<%=myConnection.getHTMLFormattedList("ftp.jsp") %>

Return to default directory

The FTPConnection object used by the JSP page is fairly straightforward, as shown in Figure 4-3. Iverson_ch04.qxd 1/17/05 2:39 PM Page 50 50 Net Chapter 4 Figure 4-3 FTPConnection class. The code for FTPConnection is shown in Listing 4-2. Listing 4-2 FTP Connectivity Code package com.cascadetg.ch04; import java.util.Date; import java.util.StringTokenizer; import org.apache.commons.net.ftp.*; public class FTPConnection { /** * The FTP client implementation. Note that we don't preserve * the client between executions - doing so would significantly * improve performance, but would require more effort to ensure * synchronization. For an example of this, see the * NNTPConnection class. * * @see NNTPConnection */ FTPClient ftp = new FTPClient(); /** Initially, the connection is considered to be invalid */ boolean valid = false; /** The file listing as returned by the connection */ private FTPFile[] files; /** We don't know the working directory. If the working * directory is null, we'll assume that the default directory * as given when the user logs in is to be used. */ (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 51 FTP Implementation 51 Listing 4-2 (continued ) String workingDirectory = null; public boolean isValid() { return valid; } /** Here, we attempt to connect to the specified working * directory, get the file list, close the connection, and * return. */ public void connect() { try { // Attempt the initial connection. Note that this // happens before we even log in - here we are just // trying to establish a connection. int reply; ftp.connect(NetConnectionTokens.ftp_server); // We have to get the reply code to continue - this is // required by the library. reply = ftp.getReplyCode(); if (!FTPReply.isPositiveCompletion(reply)) { ftp.disconnect(); return; } // Now, we attempt to log in using the FTP username & // password. ftp.login( NetConnectionTokens.ftp_username, NetConnectionTokens.ftp_password); // If a working directory has been specified, we // attempt to // change to that directory if (this.workingDirectory != null) if (this.workingDirectory.length() > 0) if (this.workingDirectory.compareTo("null") != 0) valid = ftp.changeWorkingDirectory( this.workingDirectory); // If no working directory has been specified, we try // to // find out what directory we default to and use that. // Also, if we've followed a link, this might be a more // accurate report of where we "really" are. this.workingDirectory = ftp.printWorkingDirectory(); // Get the list of files from the server. files = ftp.listFiles(); valid = true; } catch (Exception e) { e.printStackTrace(); } finally (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 52 52 Net Chapter 4 Listing 4-2 (continued ) { // Regardless of any errors, we make an effort to // disconnect from the server. if (ftp.isConnected()) { try { ftp.disconnect(); } catch (Exception f) { // Silent failure here is fine. } } } } public String getWorkingDirectory() { return workingDirectory; } public void setWorkingDirectory(String workingDirectory) { this.workingDirectory = workingDirectory; } /** A command-line test method */ public static void main(String[] args) { FTPConnection myConnection = new FTPConnection(); myConnection.connect(); FTPFile[] files = myConnection.getFiles(); System.out.println( myConnection.getHTMLFormattedWorkingDirectory( "ftp.jsp")); for (int i = 0; i < files.length; i++) { System.out.println( myConnection.getHTMLFormattedFile( files[i], "ftp.jsp")); } } /** Returns the current working directory nicely formatted for * display on an HTML page. * * @param page * Specify the page the links should point to */ public String getHTMLFormattedWorkingDirectory(String page) { if (workingDirectory == null) return ""; StringBuffer result = new StringBuffer(); // Note the use of the built-in JDK tokenizer StringTokenizer tokenizer = new StringTokenizer(workingDirectory, "/", false); String built_path = ""; String current = ""; while (tokenizer.hasMoreTokens()) { current = tokenizer.nextToken(); built_path = built_path + "/" + current; (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 53 FTP Implementation 53 Listing 4-2 (continued ) result.append(""); result.append(current); result.append(""); result.append("/"); } result.append("
"); return result.toString(); } /** Returns the current file list nicely formatted for display * on an HTML page. * * @param page * Specify the page the links should point to */ public String getHTMLFormattedList(String page) { StringBuffer reply = new StringBuffer(); if (files != null) { for (int i = 0; i < files.length; i++) { if (files[i].isDirectory()) reply.append( } getHTMLFormattedFile(files[i], page)); reply.append(""); for (int i = 0; i < files.length; i++) { if (!files[i].isDirectory()) { reply.append(""); reply.append( getHTMLFormattedFile(files[i], page)); reply.append(""); } } reply.append("
"); } return reply.toString(); } /** Returns the current file nicely formatted for display on an * HTML page. Note that this is used by the * getHTMLFormattedList function, so this isn't actually used * in the JSP page. * * @param page * Specify the page the links should point to */ public String getHTMLFormattedFile(FTPFile file, String page) { StringBuffer result = new StringBuffer(); if (file.isDirectory()) (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 54 54 Net Chapter 4 Listing 4-2 (continued ) { result.append("/"); result.append(file.getName()); result.append(""); result.append("
"); } else { result.append(""); result.append(file.getName()); result.append(""); result.append((file.getSize() / 1024)); result.append("K"); result.append( new Date(file.getTimestamp().getTimeInMillis()) .toLocaleString()); result.append(""); } return result.toString(); } public FTPFile[] getFiles() { return files; } public void setFiles(FTPFile[] files) { this.files = files; } } This FTP connectivity code shown in Listing 4-2 suffers from a few obvi- ous limitations—most significantly, it opens and closes the connection every time the page is requested. Although this might be adequate for extremely light usage, it would be preferable to provide some mechanism for caching the FTP data. If this was the only mechanism provided for interaction with the FTP server, as part of a content publishing framework for example, very ag- gressive caching might be appropriate. Additional functionality, such as uploading files, could be added by folding in the code shown in Chapter 2, "File Upload." NNTP FUNCTIONALITY In this example, you will build a read-only web view of the latest posts made to the various comp.lang.java.* newsgroups. These groups are shown in Figure 4-4. In the next section, you’ll look at a simple NNTP browser and compare the simplistic open-and-close approach of the code in Listing 4-2 with a more aggressive caching mechanism. Clicking on the Most Recent Article link shows us an individual mes- sage post, as shown in Figure 4-5. An interface is provided to view earlier and Iverson_ch04.qxd 1/17/05 2:39 PM Page 55 NNTP Functionality 55 Newsgroup Organization NNTP groups are traditionally organized according to a hierarchy, with the most general name moving from left to right. For example, comp.lang.java.* can be translated to mean "all the groups under the cat- egory Computers, Languages, Java." The most infamous section of USENET are the groups under the alt.* category. Many companies have set up their own NNTP servers, independent of USENET, allowing users to post and discuss topics of interest (for example, internal discussions, or external customers discussing product issues). It’s important to keep in mind that an NNTP server can be configured to participate in exchanging one or more USENET groups, but it is by no means required. Figure 4-4 NNTP Group List. later messages (as determined by the server), and a few of the key headers are provided. It’s easy to imagine additional functionality, such as posting new mes- sages, displaying additional detail, or even showing a threaded view of the conversation, but this is a reasonable start. Iverson_ch04.qxd 1/17/05 2:39 PM Page 56 56 Net Chapter 4 Figure 4-5 Viewing a NNTP post. NNTP IMPLEMENTATION There are two JSP pages used to display the NNTP client information. The code for the group list, nntp_groups.jsp (shown rendered in the browser in Figure 4-4), can be found in Listing 4-3. Listing 4-3 NNTP Group List JSP <%@ page contentType="text/html; charset=iso-8859-1" language="java" import="com.cascadetg.ch04.*" %> <% String newsgroup_pattern = "comp.lang.java.*"; NNTPConnection myNNTPConnection = new NNTPConnection(); if(request.getParameter("refresh") != null) myNNTPConnection.refreshNewsgroupList(newsgroup_pattern); org.apache.commons.net.nntp.NewsgroupInfo[] newsgroups = myNNTPConnection.getNewsgroupList(newsgroup_pattern); %> Java Newsgroups (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 57 NNTP Implementation 57 Listing 4-3 (continued )

<%= newsgroup_pattern %>

<% for(int i = 0; i < newsgroups.length; i++) { %> <% } %>
Newsgroup Articles  
<%= newsgroups[i].getNewsgroup() %> <%= newsgroups[i].getArticleCount() %> Most Recent Article
The code in Listing 4-3 relies on the underlying org.apache.commons.net. nntp.NewsgroupInfo class for the information about the groups. Figure 4-6 shows the methods of this class. Figure 4-6 NewsgroupInfo class diagram. Iverson_ch04.qxd 1/17/05 2:39 PM Page 58 58 Net Chapter 4 Clicking on the link for the Most Recent Article displays the nntp_ message.jsp page. The listing for nntp_message.jsp is shown in Listing 4-4. Listing 4-4 NNTP Message Display JSP <%@ page contentType="text/html; charset=iso-8859-1" language="java" import="com.cascadetg.ch04.*" %> <% NNTPConnection myNNTPConnection = new NNTPConnection(); String newsgroup = request.getParameter("newsgroup"); String article = request.getParameter("article"); String header = myNNTPConnection.getArticleHeader(newsgroup, article); String body = myNNTPConnection.getArticleBody(newsgroup, article); String previousArticle = myNNTPConnection.previousArticle(newsgroup, article); String nextArticle = myNNTPConnection.nextArticle(newsgroup, article); %> <%= newsgroup %> <%= article %>
<%= newsgroup %> #<%= article %>
<% if(previousArticle != null) { %> <- Previous <% } %>  Return To Group List <% if(nextArticle != null) { %> Next -> (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 59 NNTP Implementation 59 Listing 4-4 (continued ) <% } %> 
<%= header %>

<%= body %>

Now that you’ve seen the JSP presentation code, let’s look at the underly- ing Java code. A diagram is shown in Figure 4-7. Figure 4-7 NNTP Connection example classes. Looking at the NNTPConnection code shown in Listing 4-5, you’ll notice that several java.util.Hashtable objects are used to cache the content retrieved. As NNTP is typically read-and-post, but messages are rarely deleted, this is a reasonable approach. Other NNTP clients cache data on disk or in a database. You’ll also notice the liberal use of the synchronized keyword to avoid con- tention over the use of the NNTPClient object—it’s important for certain com- mands to be issued in sequence. For example, the NNTPConnection.nextArticle() Iverson_ch04.qxd 1/17/05 2:39 PM Page 60 60 Net Chapter 4 method issues a client.selectNewsgroup() call and then immediately issues client.selectNextArticle() and client.selectArticle(). If these calls were to be intermixed with other connections, the wrong data might be returned. Listing 4-5 NNTP Connection Example package com.cascadetg.ch04; import org.apache.commons.net.nntp.*; // http://nagoya.apache.org/bugzilla/show_bug.cgi?id=26282 public class NNTPConnection { /** * This class attempts to improve performance over the * FTPConnection class by using a single static client to * retrieve data. It caches some of the data in-memory. You'll * notice that this cache code adds significant complexity, * however. */ static org.apache.commons.net.nntp.NNTPClient client = new org.apache.commons.net.nntp.NNTPClient(); /** These serve as our in-memory cache of retrived data */ static NewsgroupInfo[] newsgroups = null; static java.util.Hashtable article_bodies = new java.util.Hashtable(); static java.util.Hashtable article_headers = new java.util.Hashtable(); static java.util.Hashtable article_pointers = new java.util.Hashtable(); /** Gets the latest newsgroup list, ignoring the cache */ public void refreshNewsgroupList(String newsgroup_pattern) { checkConnection(); try { synchronized (client) { newsgroups = client.listNewsgroups(newsgroup_pattern); } } catch (Exception e) { e.printStackTrace(); } } /** Gets the latest articleID, given a newsgroup name */ public int getRecentArticleID(String newsgroup) { for (int i = 0; i < newsgroups.length; i++) { if (newsgroups[i].getNewsgroup().compareTo(newsgroup) == 0) return newsgroups[i].getLastArticle(); } return -1; } (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 61 NNTP Implementation 61 Listing 4-5 (continued ) /** Gets the list of newsgroups, from the cache if possible */ public NewsgroupInfo[] getNewsgroupList(String newsgroup_list) { if (newsgroups == null) refreshNewsgroupList(newsgroup_list); return newsgroups; } /** Gets an article pointer given a newsgroup and articleID. */ ArticlePointer getArticlePointer( String newsgroup, String articleID) { if (article_pointers.containsKey(newsgroup + articleID)) return (ArticlePointer)article_pointers.get( newsgroup + articleID); checkConnection(); ArticlePointer newPointer = new ArticlePointer(); String result = ""; try { synchronized (client) { client.selectNewsgroup(newsgroup); client.selectArticle(articleID); getAsString( client.retrieveArticleBody( articleID, newPointer), false); } article_pointers.put(newsgroup + articleID, newPointer); return newPointer; } catch (Exception e) { result = "Unable to retrive."; e.printStackTrace(); } return null; } /** * Gets the next article given a current article. Note that * this method relies on the server to provide the previous and * next article information. */ public String nextArticle(String newsgroup, String articleID) { if (articleID == null) return null; ArticlePointer myPointer = new ArticlePointer(); checkConnection(); try (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 62 62 Net Chapter 4 Listing 4-5 (continued ) { synchronized (client) { client.selectNewsgroup(newsgroup); client.selectArticle(Integer.parseInt(articleID)); if (!client.selectNextArticle(myPointer)) return null; client.selectArticle( myPointer.articleNumber, myPointer); } } catch (Exception e) { e.printStackTrace(); } return myPointer.articleNumber + ""; } /** See nextArticle for more information. */ public String previousArticle( String newsgroup, String articleID) { } if (articleID == null) return null; ArticlePointer myPointer = new ArticlePointer(); checkConnection(); try { synchronized (client) { client.selectNewsgroup(newsgroup); client.selectArticle(Integer.parseInt(articleID)); if (!client.selectPreviousArticle(myPointer)) return null; client.selectArticle( myPointer.articleNumber, myPointer); } } catch (Exception e) { e.printStackTrace(); } return myPointer.articleNumber + ""; /** Gets the body of an article, preferably from the cache */ public String getArticleBody( String newsgroup, String articleID) { if (article_bodies.containsKey(newsgroup + articleID)) return (String)article_bodies.get( newsgroup + articleID); checkConnection(); String result = ""; try (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 63 NNTP Implementation 63 Listing 4-5 (continued ) { synchronized (client) { client.selectNewsgroup(newsgroup); client.selectArticle(articleID); result = getAsString( client.retrieveArticleBody(articleID), true); } article_bodies.put(newsgroup + articleID, result); } catch (Exception e) { result = "Unable to retrive."; e.printStackTrace(); } return result; } /** Gets the header of an article, preferably from the cache */ public String getArticleHeader( String newsgroup, String articleID) { if (article_headers.containsKey(newsgroup + articleID)) return (String)article_headers.get( newsgroup + articleID); String result = ""; try { checkConnection(); synchronized (client) { client.selectNewsgroup(newsgroup); client.selectArticle(articleID); result = getAsString( client.retrieveArticleHeader(articleID), false); } java.util.StringTokenizer myTokenizer = new java.util.StringTokenizer(result, "\n", true); result = ""; while (myTokenizer.hasMoreTokens()) { String current = myTokenizer.nextToken(); current = Utilities.replaceToken(current, "<", "<"); current = Utilities.replaceToken(current, ">", ">"); if (current.startsWith("From:")) result = result + current + "
"; (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 64 64 Net Chapter 4 Listing 4-5 (continued ) if (current.startsWith("Subject:")) result = result + current + "
"; if (current.startsWith("Date:")) result = result + current + "
"; } article_headers.put(newsgroup + articleID, result); } catch (Exception e) { result = "Unable to retrive."; e.printStackTrace(); } return result; } /** The various body & header methods return Readers, not * Strings. This utiltiy method converts from a Reader to a * String, and also performs some basic HTML formatting if * requested. */ public String getAsString(java.io.Reader in, boolean HTML) { if (in == null) return ""; java.io.BufferedReader bufferedReader = new java.io.BufferedReader(in); StringBuffer temp = new StringBuffer(); boolean read = true; String current = ""; while (read) { try { current = bufferedReader.readLine(); } catch (Exception e) { read = false; } if (current != null) { current = current + "\n"; if (HTML) { current = Utilities.replaceToken( current, "<", "<"); current = Utilities.replaceToken( current, ">", ">"); temp.append(current); temp.append("
"); } else { temp.append(current); } } else read = false; } return temp.toString(); } /** Verifies that the NNTP connection is valid, and attempts to * reestablish if not. */ (continues) Iverson_ch04.qxd 1/17/05 2:39 PM Page 65 NNTP Implementation 65 Listing 4-5 (continued ) protected synchronized void checkConnection() { if (client.isConnected()) { synchronized (client) { try { client.stat(); return; } catch (Exception e) { // Ok, failed, so let's try to reconnect. try { client.disconnect(); } catch (Exception e1) { // No need to report this } } } } try { synchronized (client) { client.connect(NetConnectionTokens.nntp_server); client.getReplyCode(); client.authenticate( NetConnectionTokens.nntp_username, NetConnectionTokens.nntp_password); } } catch (Exception e) { System.err.println("Unable to connect to NNTP server!"); e.printStackTrace(); } } public synchronized void close() { try { synchronized (client) { client.logout(); } } catch (Exception e) { // Silent failure. } try { synchronized (client) { client.disconnect(); } } catch (Exception e) { // Silent failure. } } } Iverson_ch04.qxd 1/17/05 2:39 PM Page 66 66 Net Chapter 4 In a "real" NNTP client application, one can think of all sorts of additional features, such as preloading and sorting the headers on another thread, per- haps providing a threaded view of the messages, and interweaving the replies (for more information on NNTP message threading, see http://nagoya. apache.org/bugzilla/show_bug.cgi?id=26282). Tip: If you are interested in setting up your own NNTP server, you may want to investigate James, http://james.apache.org/, a Java-based SMTP, POP3, and NNTP server. SUMMARY In this chapter, two approaches for dealing with the Jakarta Commons libraries were presented. It’s easy to envision much more sophisticated approaches, with complex clients performing specialized operations. For exam- ple, an FTP client could synchronize between a remote server and a local file system, or an NNTP client might generate automated status posts. As you can see, resource management quickly becomes important when working with these protocols. A connection to a service is an important resource, as is the data that is transmitted. In the next chapter, a library that provides additional scalability and availability for database connectivity through the use of a database connection pool will be examined. Project Ideas Use Net components in conjunction with the FileUpload package (described in Chapter 2) to allow users to post files to an FTP server via a browser. Build web browser interfaces to the various protocols. Some of these (such as Telnet) imply state to be presented to the user; others (such as Finger) do not. How does this affect building a web interface? Try using TFTP and ZeroConf (also known as Rendezvous) to build a simple file local network sharing application. Iverson_ch05.qxd 1/17/05 2:40 PM Page 67 C H A P T E R 5 Pool Not all Java objects are created equal. For example, some take considerably longer to create than others—an object that establishes a secure network con- nection can take several seconds to properly initialize. Other objects might consume significant resources. In order to minimize the creation of these objects, you may want to maintain a pool of objects—a little bit of bookkeeping to keep track of a group of objects, checked out and returned as needed. The Apache Jakarta Commons Pool package provides interfaces and implementa- tion to make that task much easier. Although some people might think that an object pool is easy to write, by using the Pool package, a wide suite of built-in, well-tested behaviors is pro- vided for free. For example, you can use the Commons package to create a pool that will only allocate a maximum of ten objects and then block on future allo- cations until an object is returned or create up to fifty objects, with the pool automatically shrinking when the garbage collector needs the memory. By implementing a single interface and using the right combination of Apache Pool interfaces and implementations, you can configure a wide suite of pools, suitable for a broad range of uses. Avoid Preoptimization Maintaining an object pool simply to minimize the overhead of JVM-level object creation is generally not worth the bother. Modern JVM implemen- tations are quite good at optimizing object creation. If the objects are expensive to create, however, it may be worth creating a pool. It’s worth noting that one of the most popular uses of a pool is to manage database connectivity. This is popular enough to warrant a specific Commons package, DBCP, which is based on the Pool suite described in this chapter. DBCP is described in the next chapter. In addition, Java 5.0 (also known as JDK 1.5) includes built-in support for ThreadPools and other useful opera- tions, as described at http://java.sun.com/j2se/1.5.0/docs/guide/concurrency/ index.html. 67 Iverson_ch05.qxd 1/17/05 2:40 PM Page 68 y t y . y h c r a r e i h s s a l c l o o p c i r e n e G 1 - 5 e r u g F i t t l 68 Iverson_ch05.qxd 1/17/05 2:40 PM Page 69 Thread Pool Example 69 INTERFACES AND IMPLEMENTATION The Pool library provides both a suite of interfaces and a set of concrete imple- mentations. This allows a developer to maintain compatibility with a wide variety of applications, while also adding new functionality as needed. In turn, the Pool library contains two hierarchies—one for a generic pool, and one for keyed pools. The hierarchy for generic pools is shown in Figure 5-1. The semantics for an object pool are fairly straightforward—you must first implement the interface org.apache.commons.pool.PoolableObjectFactory (a no- operation abstract class, org.apache.commons.pool.BasePoolableObjectFactory, can be subclassed if preferred). At a minimum, you will need to provide an implementation of the makeObject() method, to define how and what should be created. Next, you will need to create an ObjectPool. You can create an ObjectPool by using an ObjectPoolFactory or simply by allocating it using new, passing your PoolableObjectFactory implementation in to the constructor. Depending on the ObjectPool implementation you use, your object pool will have different behavior. The GenericObjectPool uses a first in, first out behavior, suitable for situations in which you want to ensure that all of the objects are used fre- quently. The StackObjectPool, on the other hand, uses a last in, first out behav- ior. A useful alternative to the StackObjectPool is the SoftReferenceObjectPool, which allows garbage collection of unused objects. The KeyedObjectPool hierarchy, as shown in Figure 5-2, is similar to the GenericPool, but with the addition of a key value. This allows you to maintain a single pool with the elements retrievable by key. The default implementa- tions allow one or more objects per key, but you could provide an implementa- tion that restricts use to a single object per key. THREAD POOL EXAMPLE Java features a powerful, rich set of services for working with multiple threads. In this example, we will use the Pool suite to manage experimenta- tion with the built-in Java threading facilities. As shown in Figure 5-3, a WorkerThreadFactory can be used to provide new test thread objects. Our main application code, PoolTest, creates a suite of test threads, testing how long it takes to complete the test run in different combi- nations of threads and thread runs. By changing the behavior of the WorkerThread.run() method, we can change the load placed on the system by each thread, and by changing the val- ues of the PoolTest.runTest() method, we can determine different results when different thread loads are placed on the system. For example, by com- paring the impact of 1,000 threads running once against a single thread run- ning the same task 1,000 times, we start to understand the overhead of parallel execution on a single system compared to serial execution. Iverson_ch05.qxd 1/17/05 2:40 PM Page 70 . y h c r a r e i h s s a l c l o o p d e y e K 2 - 5 e r u g F i 70 Iverson_ch05.qxd 1/17/05 2:40 PM Page 71 Thread Pool Example 71 Figure 5-3 Thread pool example classes. Iverson_ch05.qxd 1/17/05 2:40 PM Page 72 72 Pool Chapter 5 Listing 5-1 shows the main class for this example. Pay particular atten- tion to the configuration of the GenericObjectPool object in the runTest() method—notice that several important configuration methods are used to set the operation of the pool. You’ll also notice that in this example, runTest() bor- rows objects from the pool but doesn’t return them—the WorkerThread objects return themselves to the pool when execution is complete. Listing 5-1 Thread Test Runner package com.cascadetg.ch05; import org.apache.commons.pool.impl.GenericObjectPool; public class PoolTest extends Thread { /** This main method simply creates a new PoolTest thread * and starts it. */ public static void main(String[] args) { new PoolTest().start(); } /** The run() method (called when the PoolTest thread starts) * merely executes a series of test in serial fashion. */ public void run() { runTest(30, 30); runTest(100, 100); runTest(1000, 1000); runTest(1000, 2000); runTest(1, 3000); runTest(10, 3000); runTest(30, 3000); runTest(1000, 3000); System.out.println("Most efficient @" + mostEfficientTime); System.out.println( "(" + mostEfficientThreads + "/" + mostEfficientRuns + ")"); System.out.println("Done."); } /** Used to keep track of the most efficient run */ int mostEfficientThreads = 0; int mostEfficientRuns = 0; float mostEfficientTime = 0; /** This method actually runs the test. The higher the * maxThreads value, the more threads can be created to run in * parallel. The threadRuns indicates the total number of * threads that will be created. * * @param maxThreads Used to specify the maximum number (continues) Iverson_ch05.qxd 1/17/05 2:40 PM Page 73 Thread Pool Example 73 Listing 5-1 (continued ) * of threads to be created by the object pool. * * @param threadRuns The number of executions of the thread * to be run. */ public void runTest(int maxThreads, int threadRuns) { System.out.println( "Starting " + maxThreads + "/" + threadRuns); // Create an instance of our WorkerThreadFactory. WorkerThreadFactory myFactory = new WorkerThreadFactory(); // Here, we create a generic object pool, passing in our // WorkerThreadFactory. GenericObjectPool myPool = new GenericObjectPool(myFactory); // Here, we configure the behavior of our pool. // Note the use of maxThreads to configure the number of // threads we want to allocate, and the behavior of the // threads. myPool.setMaxActive(maxThreads); myPool.setWhenExhaustedAction( GenericObjectPool.WHEN_EXHAUSTED_BLOCK); myPool.setTestOnReturn(true); // Gather the current timing info, and start making // threads. Note that this will block if there is no // thread available. long currentTime = System.currentTimeMillis(); for (int i = 0; i < threadRuns; i++) { try { WorkerThread myThread = (WorkerThread)myPool.borrowObject(); myThread.setPool(myPool); myThread.start(); } catch (Exception e) { e.printStackTrace(); } } // Now, make sure that all of the threads we kicked off // have a chance to finish up what they are doing. while (myPool.getNumActive() > 0) { yield(); } // Let's do some reporting of the results. long time = System.currentTimeMillis() - currentTime; System.out.println( "Total created threads:" + myFactory.currentThread); System.out.println("Seconds Elapsed: " + (time / 1000f)); System.out.println( "Completed: " + WorkerThread.totalUnits); float efficiency = WorkerThread.totalUnits / (time / 1000f); (continues) Iverson_ch05.qxd 1/17/05 2:40 PM Page 74 74 Pool Chapter 5 Listing 5-1 (continued ) System.out.println("units/second: " + efficiency); // If this is our most efficient run, we should note that. if (efficiency > mostEfficientTime) { mostEfficientTime = efficiency; mostEfficientThreads = maxThreads; mostEfficientRuns = threadRuns; } System.out.println(); // Reset the work done by the threads for the next test. WorkerThread.totalUnits = 0; } } OBJECT FACTORY EXAMPLE The object factory, shown in Listing 5-2, implements the PoolableObjectFactory interface. The two key methods implemented are makeObject() and validateObject(). The factory always returns false for an invalid object because when a thread enters a finished state, it cannot be reused. Because the pool is configured to always test on return (as shown in Listing 5-1), this means that the WorkerThread will be removed when completed. Listing 5-2 Thread Factory package com.cascadetg.ch05; import org.apache.commons.pool.PoolableObjectFactory; public class WorkerThreadFactory implements PoolableObjectFactory { /** Keeps track of the currently created thread. */ public int currentThread = 0; /** Create and name the thread. Naming the thread is very * helpful when trying to debug multi-threaded applications. */ public Object makeObject() throws Exception { WorkerThread temp = new WorkerThread(); temp.setName("Worker Thread #" + currentThread++); return temp; } /** We aren't reusing threads, so we always return false here, * causing the pool to remove this thread from the pool and * create a new object using the makeObject() method. */ public boolean validateObject(Object arg0) { return false; } public void destroyObject(Object arg0) throws Exception { } (continues) Iverson_ch05.qxd 1/17/05 2:40 PM Page 75 Worker Thread 75 Listing 5-2 (continued ) public void activateObject(Object arg0) throws Exception { } public void passivateObject(Object arg0) throws Exception { } } WORKER THREAD Listing 5-3 shows our worker thread. The default implementation merely counts to 1,000, yielding every count. This is overly aggressive, but it does allow the system to remain highly responsive to other threads during execu- tion. It’s easy to imagine changing the behavior of this worker thread to do something more computationally complex—for example, when used in con- junction with the networking capabilities shown in Chapter 4, "Net" and this chapter, parallel execution could well be much faster and easier. The implementation shown in Listing 5-3 drops out of the run() method when complete, rendering the thread no longer reusable. It would be possible to create a reusable WorkerThread—instead of completing and dropping out of the run() method, the thread could instead have two states—a busy state and an idle state, with the thread returning itself to the pool when switching from the busy state to idle. Listing 5-3 Worker Thread package com.cascadetg.ch05; import org.apache.commons.pool.ObjectPool; public class WorkerThread extends Thread { // The total amount of work done by the threads. static public long totalUnits = 0; // The number of times the thread should look over a counter // (this is our definition of work) private int counter = 1000; // When the thread is done, it returns itself to the pool. private ObjectPool hostPool = null; // Used to indicate that a thread, when completed, is no longer // useful. public boolean valid = true; public void setPool(ObjectPool myPool) { hostPool = myPool; } public void run() { // Loop over a counter, and yield each time to allow other // threads to execute. In a "real" app, you wouldn't need // to yield anywhere near this often. for (int i = 0; i < counter; i++) (continues) Iverson_ch05.qxd 1/17/05 2:40 PM Page 76 76 Pool Chapter 5 Listing 5-3 (continued ) totalUnits++; yield(); { } try { // We synchronize on the pool to avoid possible // threading problems, and return our object. synchronized (hostPool) { this.valid = false; hostPool.returnObject(this); } } catch (Exception e) { e.printStackTrace(); } } } Finally, Listing 5-4 shows an example of the output of this application. Pay- ing close attention to the output, we can see that in this particular case, a non-parallel approach has the best timing. This is to be expected in a CPU- dependent, single system environment, but in environments involving poten- tially slow resources (such as network access), the results may be quite different. Listing 5-4 Sample Output Starting 30/30 Total created threads:30 Seconds Elapsed: 0.191 Completed: 30000 units/second: 157068.06 Starting 100/100 Total created threads:100 Seconds Elapsed: 0.801 Completed: 100000 units/second: 124843.945 Starting 1000/1000 Total created threads:1000 Seconds Elapsed: 9.794 Completed: 1000000 units/second: 102103.33 Starting 1000/2000 Total created threads:2000 Seconds Elapsed: 19.127 Completed: 2000000 units/second: 104564.23 Starting 1/3000 Total created threads:3000 Seconds Elapsed: 5.398 Completed: 3000000 units/second: 555761.44 (continues) Iverson_ch05.qxd 1/17/05 2:40 PM Page 77 Summary 77 Listing 5-4 (continued ) Starting 10/3000 Total created threads:3000 Seconds Elapsed: 6.85 Completed: 3000000 units/second: 437956.22 Starting 30/3000 Total created threads:3000 Seconds Elapsed: 7.641 Completed: 3000000 units/second: 392618.78 Starting 1000/3000 Total created threads:3000 Seconds Elapsed: 28.471 Completed: 3000000 units/second: 105370.375 Most efficient @ 555761.44 (1/3000) Done. SUMMARY This chapter shows how to use an implementation of a common pattern—the use of a pool. Pools typically serve one of two roles—either as a logical repre- sentation of a pool, or as a performance enhancement by way of a cache imple- mentation. If a pool represents a logical pool, you should feel free to use the pattern immediately—for example, an application for reserving hotel rooms might use a pool to track the available rooms. If a pool represents a cache of some sort, it should be added to an application later rather than sooner to avoid premature optimization. Pools are commonly used as a performance enhancement for manag- ing connections to a database. The next chapter will look at a specific pool designed for managing database-specific resources. Project Ideas Build an application that uses the Pool package to wrap Net NNTP con- nections (as described in Chapter 4). Add a user interface to allow a user to browse the NNTP articles on one thread and then a configurable num- ber of other threads to download articles in the background. Build a test harness that tests the size and options available for differ- ent pools against the factories. Given this information and other data available to a running Java application (such as the current memory available), would it be possible to build a self-tuning pool? Iverson_ch05.qxd 1/17/05 2:40 PM Page 78 Iverson_ch06.qxd 1/17/05 2:35 PM Page 79 C H A P T E R 6 DBCP (Database Connection Pool) Opening a connection to a database is a relatively expensive operation. To avoid having to frequently open database connections, many applications rely on a database connection pool—a group of connections to the database, rotated between the various components of an application as needed. The Apache Jakarta Commons Database Connection Pool (DBCP) provides a rich set of functionality for connection pooling. Note: Most modern application servers include built-in database con- nection pooling functionality. If you are building an application that you intend to host in an application server, consult your server documentation for more information on the preferred connection pool mechanism. DBCP offers a variety of mechanisms for managing your database con- nection pool. As shown in Figure 6-1, the pool library mimics many aspects of the normal JDBC interfaces. The best option for your application will likely depend on the environment and your existing application code (if any). If you have an existing application that accesses a database directly (for example, a Swing application that opens JDBC connections directly to a data- base1), you may wish to take advantage of DBCP’s PoolingDriver class—you can register a pool as a driver, and as long as your application code can easily be converted to using a new set of JDBC connection parameters, you can quickly add database connection pooling. Depending on the classes and config- uration chosen, a wide suite of possible options is available. 1. Perhaps even a bundled in-process Java database, such as hsqldb (http://hsqldb.sourceforge.net/) or Apache Derby (http://incubator. apache.org/derby/). 79 Iverson_ch06.qxd 1/17/05 2:35 PM Page 80 . s e c a f r e t n i C B D J d n a P C B D 1 - 6 e r u g F i 80 Iverson_ch06.qxd 1/17/05 2:35 PM Page 81 Standalone DataSources 81 Note: While the Apache DBCP code includes reference to logging, this functionality is deprecated (and the current implementation lacks certain key features). Future releases of Apache Commons DBCP may include pluggable mechanisms (for example, event listeners) for more sophisticated notification of pool behavior. Most web applications, however, rely on a javax.sql.DataSource for their database connectivity, typically obtained via a JNDI lookup. The DataSource con- figuration in this case is managed by the application server configuration. For example, Tomcat allows you to configure JDBC connection pools as shown at http://jakarta.apache.org/tomcat/tomcat-5.0-doc/jndi-resources-howto.html. If you are using Tomcat as the provider of your DataSource objects, you’re using the Commons DBCP package, even though you may never need to know (or care) about the underlying implementation. STANDALONE DATASOURCES Under certain circumstances, however, you may not have the option of deploying (or testing) application code within the context of your application server, but you might still want to rely on a pooled javax.sql.DataSource for your connectivity. Here, we will look at an example of executing an applica- tion that makes use of a custom DataSource—and test to see just how much of a performance improvement pooling a series of database connections affords an application. Figure 6-2 shows our two classes—a series of worker threads, executing a test SQL string, and a test harness to create the shared DataSource. Client Connectivity As shown in Listing 6-1, our worker thread is given a connection at creation, runs the test SQL, and then carefully returns the connection. There is no ref- erence to a DataSource or any notion of how the connection is obtained—the thread merely runs the code and terminates. In many ways, this is similar to the activity of a typical web application as might be found in a JSP, servlet, or when using EJB’s Bean-Managed Persistence. Iverson_ch06.qxd 1/17/05 2:35 PM Page 82 82 DBCP (Database Connection Pool) Chapter 6 Figure 6-2 Testing pooled versus non-pooled JDBC connectivity. Listing 6-1 Simple Database Connectivity package com.cascadetg.ch06; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class PerformConnection extends Thread { // The test SQL we are sending to the database. private static final String testSQL = "SELECT NOW()"; Connection connection; // Note that by providing this constructor, the compiler will not // generate a no-op default constructor for us. PerformConnection(Connection myConnection) (continues) Iverson_ch06.qxd 1/17/05 2:35 PM Page 83 Standalone DataSources 83 Listing 6-1 (continued ) { } this.connection = myConnection; public void run() { Connection myConnection = connection; Statement myStatement = null; ResultSet myResult = null; try { // There's no advantage to creating a prepared // statement for a simple SQL statement such as NOW() myStatement = myConnection.createStatement(); myResult = myStatement.executeQuery(testSQL); // Get the resulting data back, and loop through it // to simulate the data retrieval. int numcols = myResult.getMetaData().getColumnCount(); while (myResult.next()) { for (int i = 1; i <= numcols; i++) { myResult.getString(i); } } } catch (SQLException e) { e.printStackTrace(); } finally { // We want to be agressive about ensuring that our // connection is properly cleaned up and returned to // our pool. try { myResult.close(); } catch (Exception e) { } try { myStatement.close(); } catch (Exception e) { } try { myConnection.close(); } catch (Exception e) { } } } } Building the DataSource The code shown in Listing 6-2 shows how a pooled DataSource can be set up and configured. Pay attention to configuration details specified in the init() method, such as the maximum size of the pool. Listing 6-2 Simple Database Connectivity package com.cascadetg.ch06; import java.sql.DriverManager; import java.sql.Connection; import java.sql.SQLException; // commons-dbcp.jar import org.apache.commons.dbcp.cpdsadapter.DriverAdapterCPDS; (continues) Iverson_ch06.qxd 1/17/05 2:35 PM Page 84 84 DBCP (Database Connection Pool) Chapter 6 Listing 6-2 (continued ) //Note that the SharedPoolDataSource relies on the //commons-collection.jar, so you will need that on your classpath //as well. import org.apache.commons.dbcp.datasources.SharedPoolDataSource; public class ConnectionPoolExample { // You'll want to change these strings for the database you're // using. This example was performed using a default // installation of the MySQL database (www.mysql.com) private static final String driver = "com.mysql.jdbc.Driver"; private static final String username = "root"; private static final String password = ""; private static final String jdbcConnection = "jdbc:mysql://localhost/commons"; private static SharedPoolDataSource sharedDatasource; static void init() { DriverAdapterCPDS myConnectionPoolDatasource = new DriverAdapterCPDS(); try { myConnectionPoolDatasource.setDriver(driver); } catch (Exception e) { } myConnectionPoolDatasource.setUrl(jdbcConnection); myConnectionPoolDatasource.setUser(username); myConnectionPoolDatasource.setPassword(password); sharedDatasource = new SharedPoolDataSource(); sharedDatasource.setConnectionPoolDataSource( myConnectionPoolDatasource); sharedDatasource.setMaxActive(10); sharedDatasource.setMaxWait(50); } public static Connection getConnection() throws SQLException { return sharedDatasource.getConnection(); } public static void main(String[] args) { init(); try { // First we fill up the pool before starting our timings for (int x = 0; x < 15; x++) { Connection conn = getConnection(); new PerformConnection(conn).start(); } long currentTiming = System.currentTimeMillis(); // Perform the SQL operation many times. Notice that // we are kicking these off as simultaneous threads, // closer to the behavior one might expect in a // multi-threaded environment such as a web application for (int x = 0; x < 1000; x++) (continues) Iverson_ch06.qxd 1/17/05 2:35 PM Page 85 Standalone DataSources 85 Listing 6-2 (continued ) { } Connection conn = getConnection(); new PerformConnection(conn).start(); while (sharedDatasource.getNumActive() > 0) { // Need to wait until all of the connections // have completed. } float timing = (System.currentTimeMillis() - currentTiming) / 1000f; System.out.println("Seconds with pool : " + timing); currentTiming = System.currentTimeMillis(); // Now, we do the same number of tests, this time // opening and closing the connection using the driver // directly. for (int x = 0; x < 1000; x++) { Connection conn = DriverManager.getConnection( jdbcConnection, username, password); new PerformConnection(conn).run(); } while (sharedDatasource.getNumActive() > 0) { // Need to wait until all of the connections // have completed. } timing = (System.currentTimeMillis() - currentTiming) / 1000f; System.out.println("Seconds without pool : " + timing); // Display some pool statistics System.out.println( "NumActive: " + sharedDatasource.getNumActive()); System.out.println( "NumIdle: " + sharedDatasource.getNumIdle()); } catch (Exception e) { e.printStackTrace(); } } } Even though the code in Listing 6-2 uses an org.apache.commons.dbcp.data- sources.SharedPoolDataSource, if needed that object could have been cast or passed as a javax.sql.DataSource. When run, this application reports the timings. An example of the output on my system, connecting to a local MySQL database, is shown in Listing 6-3. Notice that even though the pool was configured to allow up to ten possible connections, only eight are actually used—this is because the connections are returned to the pool fast enough by our client code that only eight connections are ever opened. It’s easy to imagine certain lengthy client operations that might take longer to return, causing the connection pool to grow to the maxi- mum possible size. Iverson_ch06.qxd 1/17/05 2:35 PM Page 86 86 DBCP (Database Connection Pool) Chapter 6 Listing 6-3 Sample Pooling vs. No Pooling Timings Seconds with pool : 1.542 Seconds without pool : 6.219 NumActive: 0 NumIdle: 8 As can be seen in Listing 6-3, the use of connection pooling allows the applica- tion to run the test suite in roughly one-quarter the time—not bad, consider- ing no modifications to the client code were necessary to take advantage of the pool. LEGACY JDBC DRIVER It’s common to inherit a bit of code written with neither DataSources nor connection pooling of any sort in mind at all. For a variety of reasons, it may not be feasible to change your existing program logic (beyond editing the JDBC connection strings). Fortunately, DBCP supports the notion of a PoolingDriver—an implementation of a JDBC driver that implements a con- nection pool behind the scenes. As long as your application code opens and closes connections properly, you can add connection pooling at any time. Listing 6-4 shows how a bit of legacy code can be adapted to support a connection pool. As you can see, you will still need to add a bit of code to ini- tialize the connection pool (as shown in the registerPoolingDriver() method) to your legacy application’s initialization process. Listing 6-4 Legacy JDBC Application Connection Pooling package com.cascadetg.ch06; import org.apache.commons.pool.ObjectPool; import org.apache.commons.pool.impl.GenericObjectPool; import org.apache.commons.dbcp.*; import java.sql.DriverManager; import java.sql.Driver; import java.sql.Connection; import java.sql.Statement; import java.sql.ResultSet; import java.util.Properties; public class LegacyJDBCExample { public static void main(String[] args) { registerPoolingDriver(); legacyJDBCCode(); } (continues) Iverson_ch06.qxd 1/17/05 2:35 PM Page 87 Legacy JDBC Driver 87 Listing 6-4 (continued ) /** This method represents a bit of legacy code. It's assumed that * in your "real" legacy code, you have at least broken out or can * easily change the Driver and JDBC URL. The legacy username and * password are ignored when connecting to the new pool. */ public static void legacyJDBCCode() { // Note the commented out "old driver" and "old JDBC URL" //String legacyDriver = "com.mysql.jdbc.Driver"; String legacyDriver = "org.apache.commons.dbcp.PoolingDriver"; //String legacyJdbcConnection = // "jdbc:mysql://localhost/commons"; String legacyJdbcConnection = "jdbc:apache:commons:dbcp:example"; // The legacy username and password are ignored String legacyUsername = "ralph"; String legacyPassword = "bingo"; Connection myConnection = null; try { Driver myDriver = (Driver)Class.forName(driver).newInstance(); // The connection is obtained as before, but now the // connection comes from the pool. myConnection = DriverManager.getConnection( legacyJdbcConnection, legacyUsername, legacyPassword); Statement myStatement = myConnection.createStatement(); String testSQL = "SELECT NOW()"; ResultSet myResults = myStatement.executeQuery(testSQL); while (myResults.next()) { System.out.println(myResults.getString(1)); } myResults.close(); myStatement.close(); } catch (Exception e) { e.printStackTrace(); } finally { if (myConnection != null) try { // When closed, the connection is returned // to the pool. If your legacy code doesn't // do this, eventually the pool will starve - // although you are likely already running into // problems. myConnection.close(); } catch (Exception x) { } } } (continues) Iverson_ch06.qxd 1/17/05 2:35 PM Page 88 88 DBCP (Database Connection Pool) Chapter 6 Listing 6-4 (continued ) // These are the real database connectivity strings, // used by the pool. private static final String driver = "com.mysql.jdbc.Driver"; private static final String username = "root"; private static final String password = ""; private static final String jdbcConnection = "jdbc:mysql://localhost/commons"; public static void registerPoolingDriver() { // An object pool is used to maintain the connections. Any // pool may be used - for more information, see chapter 6 ObjectPool connectionPool = new GenericObjectPool(null); // The connection pool factory can pass properties on // as needed. The obvious candidates are username and // password, others will depend on your database, driver, // etc. Properties myDriverConnectionProps = new Properties(); myDriverConnectionProps.put("username", username); myDriverConnectionProps.put("password", password); // The factory is used by the driver to create new // JDBC connections, based on the driver provided. ConnectionFactory connectionFactory = null; try { Class.forName(driver); Driver myDriver = (Driver)Class.forName(driver).newInstance(); connectionFactory = new DriverConnectionFactory( myDriver, jdbcConnection, myDriverConnectionProps); // The PoolableConnectionFactory wraps the actual // Connections created by the ConnectionFactory // with pooling driver classes that implement the // pooling functionality. PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory( connectionFactory, connectionPool, null, null, false, true); // Next, attach our pooling driver as a registered driver Class.forName("org.apache.commons.dbcp.PoolingDriver"); PoolingDriver driver = (PoolingDriver)DriverManager.getDriver( "jdbc:apache:commons:dbcp:"); // Associate the identifier example with this connection // pool. We might register two different pools for // different database connectivity options. driver.registerPool("example", connectionPool); } catch (Exception e) { e.printStackTrace(); } } } Iverson_ch06.qxd 1/17/05 2:35 PM Page 89 Summary SUMMARY 89 This chapter shows how to use a custom pool as a performance enhancement for managing connections to a database. Interestingly, this can be done ex- plicitly as a pool, or implicitly by injecting the pool at the driver level. While the Pool package, described in Chapter 5, "Pool," can be used to build generic pools, the DBCP is custom-built to address the common task of connecting to a database. Project Ideas Given a Swing application that accesses a database in some fashion, add a user interface element that displays the number of database connections currently in use (perhaps a "throbber" similar to the network connection user interface widget in a web browser). Given a trivial SQL statement, write a utility to check the performance of DBCP versus opening and closing connections explicitly via JDBC. If you have an application container (such as Apache Jakarta Tomcat) that provides a connection pool (perhaps obtainable via JNDI), how does the performance compare? Iverson_ch06.qxd 1/17/05 2:35 PM Page 90 Iverson_ch07.qxd 1/17/05 2:36 PM Page 91 C H A P T E R 7 BeanUtils One of the most popular patterns in Java is the JavaBeans component model (http://java.sun.com/products/javabeans/). Originally designed to allow visual design tools to generate AWT user interfaces, the JavaBeans specification pro- vides additional guidelines on top of the basic contracts implied by a given Java class. The JavaBeans specification provides mechanisms for methods of a Java class to be visible to a builder tool, organized into properties, methods, and events. A property is available via accessor methods, such as String getFirstName() and void setFirstName(). Methods are ordinary Java methods. Events define standard methods for allowing one component to notify one or more components of an arbitrary event. Visual development tools use these various systems to enable visual construction of user interfaces: a button is dragged onto a panel, the properties are set (such as the label and size), and events are wired (for example, clicking on the button closes the window). For server-side development, the most popular aspects of the JavaBeans specification are the constructor and property patterns. Specifically, a stan- dard JavaBean must have a no-argument constructor and get/set accessor methods corresponding to the various properties. For example, the simple JavaBean shown in Listing 7-1 has two String properties (first name, last name) and a single int property (clearance). Listing 7-1 Simple JavaBean package com.cascadetg.ch07; public class User { // Private variables private String firstName; private String lastName; private int clearance; (continues) 91 Iverson_ch07.qxd 1/17/05 2:36 PM Page 92 92 BeanUtils Chapter 7 Listing 7-1 (continued ) // Accessor methods public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public int getClearance() { return clearance; } public void setClearance(int clearance) { this.clearance = clearance; } } While the JavaBeans specification describes rules for how components should be written and the expected behavior of the tools, no implementation is pro- vided. Generally speaking, it is assumed that the low-level java.lang.reflect.* package will be used to obtain information about the Java classes, and the tool will generate code as needed. Over time, it has become clear that frameworks, not just visual design tools, can take advantage of the JavaBeans patterns. For example, the object/relational bridge framework Hibernate uses JavaBean patterns to help work with relational databases in a more natural fashion. Hibernate and FormBean Hibernate, an object/relational database integration technology, uses the JavaBeans component model as its key foundation. By combining JavaBeans with XML mapping files, a Java developer can work with com- plex relational databases quickly and easily. The inspiration for this chap- ter came from the idea that the JavaBeans model can be leveraged not just for persistence, but also for automation of user interface generation. For more information on the object/relational framework Hibernate, see my book, Hibernate: A J2EE Developer’s Guide to Database Integration (ISBN: 0321268199, Addison-Wesley Professional). While it is possible to use the low-level reflection package to deal with JavaBeans, it is easier to use the Jakarta Commons BeanUtils package. For anyone given to thinking in terms of broader architectural design and framework development, it is easy to think of other areas in which the BeanUtils package may be useful. Obviously, this package would be of interest to anyone interested in building visual development tools. Similarly, dependency injection, dynamic configuration, and runtime binding of application elements such as the user interface and other systems are all potentially of interest. In this chapter we will look at how to use the Jakarta Commons BeanUtils package to build a simple framework for converting objects based on the JavaBeans standard to HTML forms and back. Iverson_ch07.qxd 1/17/05 2:36 PM Page 93 Understanding BeanUtils 93 UNDERSTANDING BEANUTILS In many ways, BeanUtils can be considered a metadata wrapper that makes it as easy to work with a JavaBean as a Map. The properties are the keys, and prop- erty values can be set by simply setting the property as a value. For example: myUser.setName("Bob"); . . . can instead be written: BeanUtils.setProperty(myUser, "name", "Bob"); Similarly, an array of the properties available for myUser can be simply retrieved: DynaProperty[] properties = WrapDynaClass. createDynaClass(myUser.class).getDynaProperties(); This offers two key advantages: it allows you to decouple components of your application, and it allows you to build frameworks and tools to take advantage of the JavaBeans framework. As shown in Figure 7-1, the BeanUtils package draws a distinction between a DynaClass, which describes a class, and a DynaBean, which describes a particular object instance. This notion can actually be extended a bit—a DynaClass can be used as a wrapper for a JDBC ResultSet, for example (in which the properties correspond to the returned results), and individual records can be returned as DynaBeans. One aspect of the BeanUtils package worth calling out is the notion of a Converter. This provides a generic way to retrieve and set values across a suite of properties using String values, regardless of the type of the property. For example, you may want to set a property with a type of int using a String such as "2". The Converter package takes care of these details for you. The following types are supported by built-in converters: ☞ BigDecimal ☞ BigInteger ☞ Boolean ☞ Byte ☞ Character ☞ Class ☞ Double ☞ File ☞ Float ☞ Integer ☞ Long ☞ Short ☞ SqlDate ☞ SqlTime ☞ SqlTimestamp ☞ String ☞ URL ☞ Abstract array ☞ Boolean array ☞ Byte array ☞ Character array ☞ Double array ☞ Float array ☞ Integer array ☞ Long array ☞ Short array ☞ String array Iverson_ch07.qxd 1/17/05 2:36 PM Page 94 94 BeanUtils Chapter 7 Figure 7-1 BeanUtils class diagram. USING BEANUTILS TO GENERATE FORMS Given the information already present in a JavaBean, the sample application will use BeanUtils to create a new library based on a new class, FormBean. FormBean generates an HTML form directly from the JavaBean information as rendered by BeanUtils. Each property results in a single label and a single Iverson_ch07.qxd 1/17/05 2:36 PM Page 95 Using BeanUtils to Generate Forms 95 text field. The label is generated automatically from the property name (for example, getFirstName is automatically labeled First Name). When the form is submitted, FormBean will attempt to set the JavaBean properties using the sub- mitted values. Although FormBean is not a complete framework (for example, array- based properties are not supported), it does illustrate the power of JavaBeans in conjunction with BeanUtils. Sample JavaBeans This example is based on the simple JavaBean shown in Listing 7-1. Note the three properties: two of type String, one of type int. In order to demonstrate the lifecycle as handled by FormBean, the applica- tion needs to have some mechanism for storing a value. Listing 7-2 shows how the application tracks the user. Listing 7-2 Tracking the User package com.cascadetg.ch07; public class UserManager { static private User user = new User(); static public User getUser() { return user; } static public void setUser(User in) { user = in; } } Presenting the Form Given the User JavaBean, FormBean generates a form, as shown in Figure 7-2. If a user enters incorrect data for the required property type, FormBean automatically generates and reports the error, as shown in Figure 7-3. Figure 7-2 Initial FormBean form. Iverson_ch07.qxd 1/17/05 2:36 PM Page 96 96 BeanUtils Chapter 7 Figure 7-3 Handling a FormBean form error. After the user corrects any errors and resubmits the form, FormBean is used to accept the submission, as shown in Figure 7-4. Figure 7-4 Corrected FormBean form. The entire JSP file to generate and handle this form is shown in Listing 7-3. Note the .error style defined to highlight the errors. Listing 7-3 FormBean JSP <%@ page language="java" im- port="com.cascadetg.ch07.*,org.apache.commons.beanutils.*" errorPage="" %> <% FormBean myFormBean = new FormBean(User.class, UserManager.getUser()); String notification = "Welcome!"; if(request.getParameter("Submit") != null) (continues) Iverson_ch07.qxd 1/17/05 2:36 PM Page 97 Using BeanUtils to Generate Forms 97 Listing 7-3 (continued ) { if(myFormBean.updateValue(request)) notification = "Form accepted!"; else } notification = "Form incorrect: fix errors"; %> BeanUtils Demo <%= myFormBean.toHTMLForm()%>

<%= notification %>

Even a simple form with minimal update and validation logic would be painful to implement by hand with JSP. For a web application with dozens of such forms, a lot of tedious work could be eliminated through the use of a frame- work like FormBean. FormBean The initialization of the FormBean is shown in Listing 7-4. As you can see, the FormBean uses the class and optionally an instance to configure the form. If no instance is passed in, FormBean will attempt to instantiate one. Either way, the FormBean keeps track of both the original class and instance, and then it wraps the class in a DynaClass and the instance in a DynaBean (using WrapDynaClass). Listing 7-4 FormBean Initialization package com.cascadetg.ch07; import java.util.HashMap; import java.util.Map; import javax.servlet.http.HttpServletRequest; import org.apache.commons.beanutils.BeanUtils; import org.apache.commons.beanutils.DynaBean; import org.apache.commons.beanutils.DynaClass; import org.apache.commons.beanutils.DynaProperty; (continues) Iverson_ch07.qxd 1/17/05 2:36 PM Page 98 98 BeanUtils Chapter 7 Listing 7-4 (continued ) import org.apache.commons.beanutils.WrapDynaBean; import org.apache.commons.beanutils.WrapDynaClass; public class FormBean { private HashMap errors = new HashMap(); // The class refers to the compiled version of the class private Class baseClass; private DynaClass dynaClass; // The object refers to the runtime (in-memory) version private Object baseObject; private DynaBean dynaObject; private DynaProperty[] properties; // Used to help format the resulting text boxes private int displayStringLength = 40; private int maxStringLength = 100; /** For creation forms */ public FormBean(Class myClass) { baseClass = myClass; dynaClass = WrapDynaClass.createDynaClass(baseClass); properties = dynaClass.getDynaProperties(); try { baseObject = myClass.newInstance(); dynaObject = new WrapDynaBean(baseObject); } catch (Exception e) { System.err .println("FATAL ERROR: Unable to instantiate " + dynaClass.getName()); e.printStackTrace(); } } /** For update forms */ public FormBean(Class myClass, Object myObject) { baseObject = myObject; dynaObject = new WrapDynaBean(baseObject); baseClass = myClass; dynaClass = WrapDynaClass.createDynaClass(baseClass); properties = dynaClass.getDynaProperties(); } Given the class and an instance, FormBean has the information it needs to create a form. As shown in Listing 7-5, FormBean loops through the properties to gener- ate the label and the input form and to set the default values for the form based on the object instance. Note that errors are collected in a java.util.Map, with the key being the property and the value being the error message. Iverson_ch07.qxd 1/17/05 2:36 PM Page 99 Using BeanUtils to Generate Forms 99 Listing 7-5 FormBean Form Generation /** Converts the object into a simple HTML form. */ public String toHTMLForm() { StringBuffer output = new StringBuffer(); for (int i = 0; i < properties.length; i++) { String currentProperty = properties[i].getName(); if (currentProperty.compareTo("class") != 0) { // Start the row output.append(""); // The cell for the label output.append(""); output.append(FormBeanUtils .formatName(currentProperty)); output.append(""); // The cell for the input form element output.append(""); output.append(""); output.append(""); // This cell displays any errors for this // property output.append(""); if (errors.containsKey(currentProperty)) { output.append(errors.get(currentProperty) .toString()); } output.append(" "); // Finish up this row output.append(""); } } return output.toString(); } Iverson_ch07.qxd 1/17/05 2:36 PM Page 100 100 BeanUtils Chapter 7 Listing 7-6 shows how a submitted form is handled. Note that the logic is expressed in terms of a Map (not explicitly tied in to the servlet model), allow- ing the FormBean to be tested outside of the context of a container. The BeanUtils class is used to attempt to set the values of the bean using the string submitted by the user. A try/catch block wraps the conversion attempt, and failures are logged to a Map for later display to the user. Listing 7-6 FormBean Update Request /** * Returns true if all of the values pass validation. * Otherwise, returns false (the user should therefore be * prompted to correct the errors). * * The incoming Map should contain a set of values, where the * incoming values are a single key String and the values are * String[] objects. */ public boolean updateValue(Map in) { // Initialize the converters - we want format exceptions. FormBeanUtils.initConverters(); boolean isGoodUpdate = true; for (int i = 0; i < properties.length; i++) { String key = properties[i].getName(); Object value = in.get(key); try { BeanUtils.setProperty(baseObject, key, value); } catch (Exception e) { if (value != null) { errors.put(key, "Value of " + FormBeanUtils.formatName(key) + " may not be '" + ((String[]) value)[0].toString() + "'"); } else errors.put(key, "Value may not be null"); isGoodUpdate = false; } } return isGoodUpdate; } /** * Returns true if all of the values pass validation. * Otherwise, returns false (the user should therefore be * prompted to correct the errors). */ public boolean updateValue(HttpServletRequest request) { Map in = request.getParameterMap(); return this.updateValue(in); } Iverson_ch07.qxd 1/17/05 2:36 PM Page 101 Using BeanUtils to Generate Forms 101 Listing 7-7 demonstrates how the FormBean was developed—outside of a servlet container. Listing 7-7 FormBean /** * Note that this particular design allows you to test your * bean programmatically, outside of the context of a web * application server. */ public static void main(String[] args) { FormBean myFormBean = new FormBean(User.class); System.out.println(myFormBean.toHTMLForm()); User myUser = new User(); myUser.setClearance(5); myUser.setFirstName("Bob"); myUser.setLastName("Smith"); myFormBean = new FormBean(User.class, new WrapDynaBean(myUser)); System.out.println(myFormBean.toHTMLForm()); Map myMap = new HashMap(); myMap.put("firstName", new String[] { "Ralph"}); myMap.put("lastName", new String[] { "Bingo"}); myMap.put("clearance", new String[] { "5"}); myFormBean.updateValue(myMap); System.out.println(myFormBean.toHTMLForm()); myMap.remove("clearance"); myMap.put("clearance", new String[] { "invalid"}); myFormBean.updateValue(myMap); System.out.println(myFormBean.toHTMLForm()); } } FormBeanUtils A few utility methods are needed to support the FormBean, as shown in Listing 7-8. The formatName method is used to generate proper English labels from JavaBean properties. The appendAttribute method is used to ease the generation of HTML-style attribute values. Most importantly, the initConverters method is used to cause the BeanUtils property setter to throw an exception in the event of a failed conversion attempt. By default, BeanUtils will silently fail if a conversion attempt fails. By installing the con- verter as shown, failed attempts to convert a String to an int or Integer value will generate an exception. If you wish to support additional property types and generate errors for failed conversions, you can install additional converters. The BeanUtils package includes converters for all core Java types (as listed earlier in this chapter), and you can create your own customer con- verters as well. Iverson_ch07.qxd 1/17/05 2:36 PM Page 102 102 BeanUtils Chapter 7 Listing 7-8 FormBean Utilities package com.cascadetg.ch07; import org.apache.commons.beanutils.ConvertUtils; import org.apache.commons.beanutils.Converter; import org.apache.commons.beanutils.converters.IntegerConverter; public class FormBeanUtils { /** * A utility function, takes a standard JavaBean property * name and converts it to a nice US English spacing. * * For example, firstName = First Name */ public static String formatName(String in) { String result = new String(); for (int i = 0; i < in.length(); i++) { if (Character.isUpperCase(in.charAt(i))) { result = result + (" "); } result = result + (in.charAt(i) + ""); } String result2 = new String(); for (int i = 0; i < result.length(); i++) { if (Character.isDigit(result.charAt(i))) { result2 = result2 + (" "); } result2 = result2 + (result.charAt(i) + ""); } char titleChar = result2.charAt(0); String result3 = Character.toUpperCase(titleChar) + ""; result3 = result3 + (result2.substring(1, result2.length())); return result3; } /** * A utility method, used to add an attribute in the form * attribute='value' with a space afterward. */ public static void appendAttribute(StringBuffer in, String attribute, String value) { } in.append(attribute); in.append("='"); in.append(value); in.append("' "); static private boolean convertersInitialized = false; static public void initConverters() (continues) Iverson_ch07.qxd 1/17/05 2:36 PM Page 103 Summary 103 Listing 7-8 (continued ) { if (!convertersInitialized) { // No-args constructor gets the version that throws // exceptions Converter myConverter = new IntegerConverter(); // Convert the primitive values ConvertUtils.register(myConverter, Integer.TYPE); // Convert the object version ConvertUtils.register(myConverter, Integer.class); convertersInitialized = true; } } } SUMMARY This chapter shows how to leverage the JavaBeans pattern to provide richer application frameworks. This allows you to think of your application in terms of components and reusable frameworks, instead of a hard-coded monolith. By decomposing your application, it becomes easier to build, reuse, and test indi- vidual components. It’s easy to imagine building complex graphs of JavaBean objects, with complex access code required in certain situations involving collections. In the next chapter, JXPath is shown as a tool to assist in dealing with complex object graphs. Project Ideas Build a framework to test JavaBeans by inspecting the various proper- ties, setting the properties, and calling a method on the JavaBeans. How much configuration is required beyond that which can be detected from the JavaBean type information? Write an application to compare the performance of BeanUtils and Java’s built-in reflection capabilities. Does the performance of one ap- proach or another vary if different bits of information are cached? If you find the idea of FormBean intriguing but are interested in a more complete solution, check out BeanView (http://beanview.attainware.com/). As of this writing, I have posted the source for a more complete frame- work, developed as an outgrowth of writing this chapter. My expectation is to remove the form generation and rendering components and instead rely on JavaServer Faces (http://java.sun.com/j2ee/javaserverfaces/) as a more robust framework. Feedback and comments are appreciated. Iverson_ch07.qxd 1/17/05 2:36 PM Page 104 Iverson_ch08.qxd 1/17/05 2:40 PM Page 105 C H A P T E R 8 JXPath JXPath allows you to traverse complex graphs of objects quickly and tersely, using the W3C standard XPath syntax (http://www.w3.org/TR/xpath, and a tutorial is available at http://www.w3schools.com/xpath/). Although XPath was originally designed to provide a standardized mechanism for dealing with complex XML documents, JXPath extends the XPath syntax to support deal- ing with a wide variety of complex Java data types. To understand the use of JXPath, start by considering a simple hierar- chical structure of people. These people are described by Java objects based on the Person class, as shown in Figure 8-1. Notice that each Person has a gender at a minimum and optionally a mother, father, and children. Given a Person object, consider the typical Java code needed to retrieve a male grandchild of a specific child, as shown in Listing 8-1. The code involves several loops and if statements to find the desired target—difficult to write and debug. Listing 8-1 Normal Complex Java Object Retrieval Person bob = FamilyFactory.getPerson(); Iterator children = bob.getChildren().iterator(); while (children.hasNext()) { Person child = (Person)children.next(); if (child.firstName.compareTo("Jon") == 0) { Iterator grandchildren = child.getChildren().iterator(); while (grandchildren.hasNext()) { Person grandchild = (Person)grandchildren.next(); if (grandchild.getGender() .compareTo(Person.FEMALE) == 0) System.out.println(grandchild); } } } 105 Iverson_ch08.qxd 1/17/05 2:40 PM Page 106 106 JXPath Chapter 8 e Figure 8-1 Person class. The JXPath-based code shown in Listing 8-2 produces output identical to the code shown in Listing 8-1 but is significantly shorter. Listing 8-2 JXPath Complex Java Object Retrieval Person bob = FamilyFactory.getPerson(); JXPathContext context = JXPathContext.newContext(bob); String searchTerm = "children[firstName='Jon']/children[gender='female']"; System.out.println(context.getValue(searchTerm)); Obviously, the code in Listing 8-2 is much easier to write and work with, assuming you are familiar with the XPath syntax (in Listing 8-2, the searchTerm string). In this chapter, we’ll look at how to use JXPath to retrieve objects from a potentially very complex object graph. Iverson_ch08.qxd 1/17/05 2:40 PM Page 107 Setting Up the Example Object Graph 107 SETTING UP THE EXAMPLE OBJECT GRAPH Let’s look at an example set of relationships, as shown by Figure 8-2. In English, it’s possible to describe particular relationships between Bob Smith and the other people as expressed from Bob Smith’s perspective. For example, we would say that Nancy Swenson is Bob’s maternal grandmother, or that Zeppo and Mocha are Bob’s grandchildren. Olav Oliver Nancy Swenson Robert Smith Maggy Smith Parent Child Mary Johnson Bob Smith June Smith Jon Smith Willow Smith Kitty Smith Zeppo Smith Mocha Smith Figure 8-2 Bob Smith’s family tree. In Java, we can represent all of these people (and their relationships) with a set of Java objects of class Person, as shown in Listing 8-3. Notice that when an object specifies a father or mother, the relationship is made bidirec- tional (the mother or father has the referring object marked as a child). Listing 8-3 Person Class package com.cascadetg.ch08; import java.util.Hashtable; public class Person { String firstName; String lastName; (continues) Iverson_ch08.qxd 1/17/05 2:40 PM Page 108 108 JXPath Chapter 8 Listing 8-3 (continued ) Person mother; Person father; Hashtable children = new Hashtable(0); String gender; public static final String MALE = "male"; public static final String FEMALE = "female"; public Person(String gender) {this.gender = gender;} public Person(String gender, String firstName, String lastName) { this.firstName = firstName; this.lastName = lastName; this.gender = gender; } public String toString() { return this.lastName + ", " + this.firstName; } public java.util.Collection getChildren() { return children.values(); } public void addChild(Person child) { this.children.put(child.toString(), child); } public Person getFather() { return father; } public void setFather(Person father) { this.father = father; father.addChild(this); } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public Person getMother() { return mother; } public void setMother(Person mother) { this.mother = mother; mother.addChild(this); } public String getGender(){ return gender; } public void setGender(String gender) { this.gender = gender; } } Given the Person class shown in Listing 8-3, the code in Listing 8-4 creates a suite of Person objects, initializing an object hierarchy to match the family graph shown in Figure 8-2. Iverson_ch08.qxd 1/17/05 2:40 PM Page 109 Setting Up the Example Object Graph 109 Listing 8-4 Initializing Bob’s Family package com.cascadetg.ch08; public class FamilyFactory { static Person startPerson = null; public static Person getPerson() { return startPerson; } public static void initFamily() { if (startPerson != null) return; // Bob is the "heart" of the family Person bobSmith = new Person(Person.MALE, "Bob", "Smith"); startPerson = bobSmith; // Bob's father Person robertSmith = new Person(Person.MALE, "Robert", "Smith"); bobSmith.setFather(robertSmith); // Bob's mother Person maggySmith = new Person(Person.FEMALE, "Maggy", "Smith"); bobSmith.setMother(maggySmith); // Bob's sister, married Person maryJohnson = new Person(Person.FEMALE, "Mary", "Johnson"); maryJohnson.setMother(maggySmith); maryJohnson.setFather(robertSmith); // Bob's mother's mother Person nancySwenson = new Person(Person.FEMALE, "Nancy", "Swenson"); maggySmith.setMother(nancySwenson); // Bob's father's father Person olavOliver = new Person(Person.MALE, "Olav", "Oliver"); robertSmith.setFather(olavOliver); // Bob's first wife Person juneSmith = new Person(Person.FEMALE, "June", "Smith"); // Bob's three children Person kittySmith = new Person(Person.FEMALE, "Kitty", "Smith"); kittySmith.setFather(bobSmith); kittySmith.setMother(juneSmith); Person willowSmith = new Person(Person.FEMALE, "Willow", "Smith"); willowSmith.setFather(bobSmith); willowSmith.setMother(juneSmith); (continues) Iverson_ch08.qxd 1/17/05 2:40 PM Page 110 110 JXPath Chapter 8 Listing 8-4 (continued ) Person jonSmith = new Person(Person.MALE, "Jon", "Smith"); jonSmith.setFather(bobSmith); jonSmith.setMother(juneSmith); // Bob's grandchildren Person zeppoSmith = new Person(Person.MALE, "Zeppo", "Smith"); zeppoSmith.setFather(jonSmith); Person mochaSmith = new Person(Person.FEMALE, "Mocha", "Smith"); mochaSmith.setFather(jonSmith); } } EXPLORING THE HIERARCHY Given a suite of objects to explore, we need a mechanism for using JXPath to experiment with the XPath syntax. XPath is essentially a new query language, allowing you to specify queries for a hierarchical structure. It can be difficult to understand XPath when you are first starting out. To make this easier, we’ll create an interactive Swing client to test our various XPath queries against Bob’s family, starting with Bob. As shown in Figure 8-3, XPath queries can be entered in the text field at the top, and pressing return or clicking the Execute button will cause the results of the query to be displayed in the text area below. Figure 8-3 JXPath Explorer interface. Listing 8-5 shows the code for the interactive Swing client. The code uses Bob Smith as the default context for your XPath queries—all of the queries are made starting from the Bob Smith object. Note that the actual JXPath execution is performed in the executeButtonActionPerformed method. In addi- tion, keep in mind that JXPath is returning the actual Person object, not just a String, but also that the Person objects define an implementation of the toString() method, as shown in Listing 8-3. Iverson_ch08.qxd 1/17/05 2:40 PM Page 111 Exploring the Hierarchy 111 Listing 8-5 Interactive JXPath Swing Client package com.cascadetg.ch08; import java.awt.Color; public class JXPathExplorer extends javax.swing.JFrame { public JXPathExplorer() { initComponents(); } private void initComponents() { mainScrollPane = new javax.swing.JScrollPane(); resultsTextPane = new javax.swing.JTextPane(); errorLabel = new javax.swing.JLabel(); queryPanel = new javax.swing.JPanel(); queryField = new javax.swing.JTextField(); executeButton = new javax.swing.JButton(); appMenuBar = new javax.swing.JMenuBar(); fileMenu = new javax.swing.JMenu(); setTitle("JXPath Explorer"); setName("mainFrame"); addWindowListener(new java.awt.event.WindowAdapter() { public void windowClosing( java.awt.event.WindowEvent evt) { } }); exitForm(evt); mainScrollPane.setViewportView(resultsTextPane); getContentPane().add( mainScrollPane, java.awt.BorderLayout.CENTER); errorLabel.setText("Ready."); getContentPane().add( errorLabel, java.awt.BorderLayout.SOUTH); queryPanel.setLayout(new java.awt.BorderLayout()); queryField.setFont(new java.awt.Font("DialogInput", 0, 12)); queryField.setText("Enter query here"); queryField .addActionListener(new java.awt.event.ActionListener() { public void actionPerformed( java.awt.event.ActionEvent evt) { } }); queryFieldActionPerformed(evt); queryPanel.add(queryField, java.awt.BorderLayout.CENTER); (continues) Iverson_ch08.qxd 1/17/05 2:40 PM Page 112 112 JXPath Chapter 8 Listing 8-5 (continued ) executeButton.setText("Execute"); executeButton .addActionListener(new java.awt.event.ActionListener() { public void actionPerformed( java.awt.event.ActionEvent evt) { } }); executeButtonActionPerformed(evt); queryPanel.add(executeButton, java.awt.BorderLayout.EAST); getContentPane().add( queryPanel, java.awt.BorderLayout.NORTH); fileMenu.setText("File"); appMenuBar.add(fileMenu); setJMenuBar(appMenuBar); java.awt.Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize(); setBounds( (screenSize.width - 400) / 2, (screenSize.height - 300) / 2, 400, 300); } private void executeButtonActionPerformed( java.awt.event.ActionEvent evt) { org.apache.commons.jxpath.JXPathContext context; try { this.errorLabel.setText("Working..."); this.errorLabel.setForeground(Color.BLUE); this.update(this.getGraphics()); Person bob = FamilyFactory.getPerson(); context = org.apache.commons.jxpath.JXPathContext.newContext( bob); java.util.Iterator bar = context.iterate(this.queryField.getText()); StringBuffer output = new StringBuffer(); while (bar.hasNext()) { output.append(bar.next()); output.append("\n"); } this.resultsTextPane.setText(output.toString()); this.errorLabel.setText("Ok."); this.errorLabel.setForeground(Color.BLACK); this.queryField.selectAll(); (continues) Iverson_ch08.qxd 1/17/05 2:40 PM Page 113 XPath and JXPath Syntax 113 Listing 8-5 (continued ) } catch (Throwable e) { String message = e.getMessage(); if (e instanceof OutOfMemoryError) { message = "Too many results - out of memory!"; context = null; System.gc(); } if (message.length() == 0) message = "Unknown error - check log for exception"; this.errorLabel.setText(message); this.errorLabel.setForeground(Color.RED); this.queryField.selectAll(); e.printStackTrace(); } } private void queryFieldActionPerformed( java.awt.event.ActionEvent evt) { executeButtonActionPerformed(evt); } private void exitForm(java.awt.event.WindowEvent evt) { System.exit(0); } public static void main(String args[]) { new JXPathExplorer().show(); } // Variables declaration private javax.swing.JMenuBar appMenuBar; private javax.swing.JLabel errorLabel; private javax.swing.JButton executeButton; private javax.swing.JMenu fileMenu; private javax.swing.JScrollPane mainScrollPane; private javax.swing.JTextField queryField; private javax.swing.JPanel queryPanel; private javax.swing.JTextPane resultsTextPane; // End of variables declaration } XPATH AND JXPATH SYNTAX After you’ve gotten the Swing client working, you’re ready to experiment with some basic XPath queries. For this example, JXPath translates your queries into Java using JavaBean-based patterns (such as the getProperty() methods). For example, to obtain Bob’s mother, the bob.getMother() method is called. So, to obtain his grandmother using a mother/mother query, the call would effec- tively be bob.getMother().getMother(). Basic XPath Here are some additional examples of basic XPath syntax and the results. mother/mother Iverson_ch08.qxd 1/17/05 2:40 PM Page 114 114 JXPath Chapter 8 This query simply returns Bob’s grandmother. father/father Returns Bob’s grandfather. mother|father Returns Bob’s parents. Note the use of the vertical bar (|) to indicate that both properties should be retrieved. children Returns all of Bob’s children by calling the Bob object’s getChildren() method. Complex XPath In addition to basic queries, JXPath supports a full suite of XPath queries as described at http://www.w3.org/TR/xpath. It’s beyond the scope of this text to describe the full range of possible XPath queries, but you should be aware that XPath supports a variety of specialized query tokens. Some examples include: child::* Returns the following values: Smith, Jon Smith, Kitty Smith, Willow Smith, Robert Bob male Smith Smith, Maggy As can be seen, the expression child::* refers to all of the possible child attributes—not just the children as defined by our Java code, but rather the child values as expressed by object properties, including all of the chil- dren, the mother, the father, and the other properties of the Bob object. This illustrates an important concept—the notion that child and parent have par- ticular meanings in XPath based on the object graph traversal, which may or may not be conceptually the same as the parent/child relationship for your application. descendant::* This query will actually result in an out-of-memory error, as it will attempt to load all of the descendants of all of the objects. Unfortunately, attempting to load all of the descendant properties of Bob leads to an infinitely recursive loop for our particular object graph. One of the Bob object’s attributes is his father. His father, in turn, has the Bob object as a child, and so JXPath will attempt to continue loading Bob, his father, Bob, his father, and so on until all Iverson_ch08.qxd 1/17/05 2:40 PM Page 115 XPath and JXPath Syntax 115 the available memory is exhausted. If this were used to represent a finite graph, for example, an XML document, this query would operate correctly. count(children) Returns the string 3.0. This query is an example of an XPath function, used in conjunction with a node query (called a node-set in XPath). 20 mod 6 Returns the string 2.0. Another XPath function. XPath does have some sup- port for basic string and numeric functions, but these operations are often simpler, easier, and more powerful when expressed in the native programming language. concat('foo', 'bar') Returns foobar. This is another example of an XPath function. JXPath Extensions JXPath defines a few additional extensions to the XPath syntax. The most notable extensions are the ability to call arbitrary Java code, as shown in the following. Notice that the fully qualified class name is used in the query. com.cascadetg.ch08.Person.new('male', 'Indigo', 'Smith') Returns Smith, Indigo (the newly created object). The new term is used to indi- cate the class constructor for the object. com.cascadetg.ch08.FamilyFactory.getPerson() Calls the static method to return Smith, Bob. com.cascadetg.ch08.FamilyFactory.getPerson()/children Returns the values: Smith, Jon Smith, Kitty Smith, Willow This shows that you can mix the results of a Java method call with JXPath’s XPath queries. getFirstName(/) Returns Bob. Note that the first argument of the method is the object that the method should be called upon—there is no implicit this prefacing the method call. In this case, we are using the / operator, which is a reference to the base Bob object. setFirstName(/, 'Sam') Iverson_ch08.qxd 1/17/05 2:40 PM Page 116 116 JXPath Chapter 8 This query doesn’t return anything, but instead modifies the base Bob object’s first name, changing the value to Sam. This shows how JXPath can be used to modify an object. Following this up with a simple / query to obtain the Bob (now Sam) object, we can see that the name has been successfully changed. For more information on other JXPath extensions to the XPath language, see http://jakarta.apache.org/commons/jxpath/users-guide.html. SUPPORTED DATA TYPES Having shown how JXPath can be used to navigate complex hierarchies (as represented by JavaBeans), it is useful to note that JXPath can be used with a wide array of potential object types. These include: ☞ JavaBeans ☞ Arrays ☞ Collections ☞ Maps (with String keys only) ☞ DOM & JDOM ☞ DynaBeans (see Chapter 7 for more information on DynaBeans) ☞ XML Documents (via a built-in JXPath Container) Perhaps most interestingly, it’s possible to mix these different object types as you traverse an object graph. For example, your JavaBean may make refer- ence to an array of JDOM objects—which could be accessed with a single XPath query. Performance and JXPath Any specialized solution for a specific data type is likely to beat the per- formance of JXPath because JXPath is designed to work flexibly with a variety of heterogeneous object graphs (e.g., XML, DOM, JavaBeans, etc.). For example, if you wish to focus on XML only, you will likely see better performance using a technology such as Xalan’s CachedXPathAPI, http://xml.apache.org/xalan-j/. Similarly, although an XPath query may be much more terse than the same Java code, the JXPath implementation needs to use Java reflection and other technologies to obtain information at run-time that would otherwise be added by the compiler. If performance is a concern (for example, if you are working with a large server application), you may want to consider a strategy in which you cache compiled expressions (see http://jakarta.apache.org/commons/jxpath/ apidocs/org/apache/commons/jxpath/CompiledExpression.html). Note that the default implementation of JXPath does perform some minimal compiled expression caching. Iverson_ch08.qxd 1/17/05 2:40 PM Page 117 Summary SUMMARY 117 This chapter shows that complex graphs of objects can easily be navigated with a relatively terse syntax. This can be especially useful when dealing with data in a variety of types. As you build complex applications, stitching together complex graphs of objects, obtaining debugging information can sometimes be difficult (espe- cially on production systems). To address these concerns, the next chapter covers Logging. Project Ideas How hard is it to map JXPath queries to SQL? Would it be possible to pro- grammatically transform a JXPath query into a SQL query? What are some additional data types that JXPath could support? For example, can a JDBC ResultSet be represented as a JXPath data type? How would the JXPath syntax map to the ResultSet? Write a performance test application to compare JXPath access, reflec- tion, and direct method access. Iverson_ch08.qxd 1/17/05 2:40 PM Page 118 Iverson_ch09.qxd 1/17/05 2:41 PM Page 119 C H A P T E R 9 Logging There is life beyond System.out.println(). As applications become more sophisticated, it’s important to have a mechanism for managing what can eventually become a torrent of informative and debugging information issued to the console. Over time, different systems have been developed for printing messages based on the severity or importance of the message. For example, Java defines two output streams—System.out for normal messages and System.err for warning messages. Over time, a variety of toolkits have appeared to provide more sophisti- cated solutions, including Log4j (http://logging.apache.org/log4j/docs/) and the introduction of a logging toolkit in JDK 1.4 (http://java.sun.com/j2se/ 1.4.2/docs/guide/util/logging/). These logging toolkits support a variety of levels of detail for logging events, with independently configurable options for recording these events. Unfortunately, by writing directly to a specific logging package, you risk tying your application to a toolkit that may lack needed functionality. To provide for better maintainability and flexibility, the Apache Commons Logging project allows you to separate your choice of logging toolkit from your application code and provides a minimalist default logging system (if, for example, you are running on a pre-JDK 1.4 Java virtual machine and don’t have Log4j installed). TRACE LEVELS At the heart of most logging packages is the notion of different levels of mes- sages. By sorting your application’s messages into these different levels, you can provide different levels of detail. Depending on the specific logging toolkit in use, you might route certain messages to System.out or to a file on disk and simply ignore others. Logging defines several different logging levels, as shown in Table 9-1, in order of severity. 119 Iverson_ch09.qxd 1/17/05 2:41 PM Page 120 120 Logging Chapter 9 Table 9-1 Logging Levels Logging Level fatal error warn info debug trace Meaning Severe errors that cause premature termination. Expect these to be immediately visible on a status console. Other runtime errors or unexpected conditions. Expect these to be immediately visible on a status console. Use of deprecated APIs, poor use of an API, and other runtime situations that are undesirable or unexpected but that don’t necessarily represent an application failure. Expect these to be immediately visible on a status console. Interesting runtime events (startup/shutdown). Expect these to be immediately visible on a console, so be conservative and keep them to a minimum. Detailed information on the flow of the system. Expect these to be written to logs only. Even more detailed information than a debug trace. Expect these to be written to logs only. Corresponding JDK 1.4 Level SEVERE SEVERE WARNING INFO FINE FINEST USING LOGGING To use the Logging package, you’ll first add a line to each class you want to log as a reference to the logging package. So, for a class MyClass, you would add the line: private static Log log = LogFactory.getLog(MyClass.class); You’ll then make a call to the log whenever you want to make a log entry. The method name is simply the log level you want to make, with a message and an optional Throwable (Throwable is the superclass for all errors and exceptions in the Java language). It’s important to keep in mind that different logging toolkits have differ- ent capabilities for reporting, independent of the Logging API. Listing 9-1 shows the use of the Logging API. Assuming you are using JDK 1.4 or later, Listing 9-1 will use the JDK 1.4 logging package to log some messages to the console and some messages to disk. Listing 9-1 Logging Example package com.cascadetg.ch09; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; (continues) Iverson_ch09.qxd 1/17/05 2:41 PM Page 121 Using Logging 121 Listing 9-1 (continued ) import org.apache.commons.logging.impl.Jdk14Logger; public class LogGenerator { // Note that you pass in an instance of this class to the // log generator. This allows you to find the messages // generated by this class. private static Log log = LogFactory.getLog(LogGenerator.class); public static void configJDKLogger() { try { ((Jdk14Logger)log).getLogger().setLevel( java.util.logging.Level.ALL); ((Jdk14Logger)log).getLogger().addHandler( (java.util.logging.FileHandler)Class .forName("java.util.logging.FileHandler") .newInstance()); System.out.println("Added JDK 1.4 file handler"); } catch (Exception e) { System.out.println("Unable to load JDK 1.4 logging."); e.printStackTrace(); } } public static void main(String[] args) { configJDKLogger(); System.setErr(System.out); System.out.println(); System.out.println("Test fatal log"); try { String foo = null; int x = 0 / (new Integer(foo)).intValue(); } catch (Exception e) { log.fatal(e.getMessage(), e); } System.out.println(); System.out.println("Test error log"); try { Object foo = null; foo.toString(); } catch (Exception e) { log.error(e.getMessage(), e); } System.out.println(); System.out.println("Test warn log"); (continues) Iverson_ch09.qxd 1/17/05 2:41 PM Page 122 122 Logging Chapter 9 Listing 9-1 (continued ) try { Class.forName("com.cascadetg.NonexistantClass"); } catch (Exception e) { log.warn("Can't find a non-existant class!"); } System.out.println(); System.out.println("Test info log"); log.info("Starting app!"); log.info("Quitting app!"); System.out.println(); System.out.println("Test debug log"); if (1 > 2) { log.debug("1 > 2 evaluated true"); if (10 % 2 == 0) log.debug("10 % 2 is 0"); else } else { log.debug("10 % 2 is not 0"); log.debug("1 > 2 evaluated false"); } System.out.println(); System.out.println("Test trace log"); log.trace("Calling trace method."); log.trace("Calling trace method."); log.trace("Calling trace method."); log.trace("Calling trace method."); log.trace("Calling trace method."); System.out.println(); System.out.println("Log test complete."); } } LOGGING OUTPUT Running the code as shown in Listing 9-1 will produce two different output streams. First, System.out (normally, the console) will produce the output as shown in Listing 9-2. Listing 9-2 Logging Example Added JDK 1.4 file handler Test fatal log Mar 22, 2004 9:04:06 PM com.cascadetg.ch09.LogGenerator main SEVERE: null (continues) Iverson_ch09.qxd 1/17/05 2:41 PM Page 123 Logging Output 123 Listing 9-2 (continued ) java.lang.NumberFormatException: null at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.(Unknown Source) at com.cascadetg.ch09.LogGenerator.main(LogGenerator.java:44) Test error log Mar 22, 2004 9:04:06 PM com.cascadetg.ch09.LogGenerator main SEVERE: null java.lang.NullPointerException at com.cascadetg.ch09.LogGenerator.main(LogGenerator.java:56) Test warn log Mar 22, 2004 9:04:06 PM com.cascadetg.ch09.LogGenerator main WARNING: Can't find a non-existant class! Test info log Mar 22, 2004 9:04:06 PM com.cascadetg.ch09.LogGenerator main INFO: Starting app! Mar 22, 2004 9:04:06 PM com.cascadetg.ch09.LogGenerator main INFO: Quitting app! Test debug log Test trace log Log test complete. You’ll notice that the output written to System.out does not contain all of the messages—the debug and trace level information is not sent to the console. Instead, the remaining data is written to disk. By default, JDK 1.4 will write to a file called java0.log in your home directory (~ on UNIX systems, or C:\Documents and Settings\User Name on Windows 2000/XP). The default file output for JDK 1.4 is an XML file, as shown in Listing 9-3 (only one record is shown for brevity). Listing 9-3 Detailed XML Logging Output 2004-03-22T21:04:06 1080018246773 0 com.cascadetg.ch09.LogGenerator SEVERE com.cascadetg.ch09.LogGenerator main 10 null java.lang.NumberFormatException: null java.lang.Integer parseInt (continues) Iverson_ch09.qxd 1/17/05 2:41 PM Page 124 124 Logging Chapter 9 Listing 9-3 (continued ) java.lang.Integer <init> com.cascadetg.ch09.LogGenerator main 44 ... To view the XML file in a validating browser or parser, you’ll need a DTD file (or else just delete the declaration at the top of the file). You can find the contents of this file at http://java.sun.com /j2se/1.4.2/docs/guide/util/logging/overview.html#3.0—simply copy the text of the DTD into a file called logger.dtd and place it in the same directory as the log file. Figure 9-1 shows the resulting log file. Figure 9-1 XML logging output in a browser. Iverson_ch09.qxd 1/17/05 2:41 PM Page 125 Summary 125 As you can see, the generated XML file contains all of the data from the application’s run, including debug and trace data. These log files can quickly become large, but JDK 1.4 includes provisions for automatically closing and rotating files as needed. It’s easy to imagine combining these resulting log files with more sophis- ticated XML parsing and retrieval tools, such as JXPath and XPath, as described in Chapter 8, "JXPath." As a final note, significant effort is made to minimize the impact of log- ging statements on the performance of your application code. Assuming you follow proper rules for Java execution flow (in particular, avoiding the use of exceptions as a form of program flow control), your logging statements should have minimal impact on your application’s performance. SUMMARY By using the Logging package, robust configurable logging can be added to your applications. Depending on your needs, this can be used to debug your application while under development, to debug your application in production, to record performance information, or even as a mechanism for generating access or other usage log files. Logging is an example of a function that is commonly used across a wide variety of applications. In the next chapter, an even more general set of com- monly used utilities will be presented. Project Ideas Use the Logging interface to build an application that generates a wide variety of log data. Compare the performance, configurability, and details provided by log4j to the default Java logging implementation. How do var- ious types of logging affect application performance? Write a tool, perhaps using SAX, DOM, XSLT, or JDOM, to process large XML log files. What sort of useful metrics can be generated, perhaps as a summary HTML document? Iverson_ch09.qxd 1/17/05 2:41 PM Page 126 Iverson_ch10.qxd 1/17/05 2:41 PM Page 127 C H A P T E R 10 Lang Almost every development project winds up with a lot of strange little utility functions, often buried in a class named something like "Utils." Common examples include a utility function for escaping a bit of HTML or SQL, or a quick class to make it easier to return a Date object formatted to a particular locale. The Lang package is essentially a fifty-odd set of these utilities. The difficult thing about the Lang package is not any particular complex- ity, but rather simply remembering what functionality is present. In this chap- ter, we provide a general overview of the Lang package. It may seem easy to write your own utility methods, but those thirty minute one-offs can start to add up—and other developers familiar with the Lang package will immedi- ately know where to find and how to use those utility routines. The Lang package is split up into six main packages: org.apache.commons.lang org.apache.commons.lang.builder org.apache.commons.lang.enum org.apache.commons.lang.exception org.apache.commons.lang.math org.apache.commons.lang.time A wide variety of miscellaneous routines. Assists in creating consistent equals(Object), toString(), hashCode(), and compareTo(Object) methods. Support for type-safe Java enums. Provides JDK 1.4 style nested exceptions on earlier versions of the JDK. Fractions, ranges, random numbers, and some additional math-related utilities. Formatting, stopwatch, and a variety of other time-related utilities. BASE LANG CLASSES Unfortunately, the functionality in the base org.apache.commons.lang classes does not easily sort into any particular logical groups. Therefore, this section touches on each class in alphabetical order. 127 Iverson_ch10.qxd 1/17/05 2:41 PM Page 128 128 Lang Chapter 10 ArrayUtils The ArrayUtils class affords the following basic functionality: a set of immutable empty arrays corresponding to all of the various primitive types and their corresponding object types, clone operations for primitive arrays, and methods to check if an array contains a particular value. For example, the code: boolean contains = false; for(int i = 0; i < myArray.length; i++) if(myArray[i] == searchVal) contains = true; . . . can be replaced with a simple: boolean contains = ArrayUtils.contains(myArray, searchVal); In addition, indexOf methods will return the index of the search value (or -1 if the search value is not found). The lastIndexOf methods work backwards. The double versions of contains, indexOf, and lastIndexOf methods even allow for a search range tolerance. An isEquals method with support for multidimensional arrays is pro- vided. A set of reverse methods is provided to reorder arrays. The toMap method converts an object array to a java.util.Map instance. Finally, toObject and toPrimitive methods allow for easy conversion of arrays from the primi- tive version to object versions. For example: long[] vals = {1, 2, 3}; Long valObjects = ArrayUtils.toObject(vals); BitField A wide suite of operations for operating on bits. Unlike many of the other oper- ations in the base Lang package, a BitField is an actual class, not a collection of static methods. A BitField is created with an int mask, specifying the number of bits of interest. Further operations may be performed using provided methods, such as clearing and setting particular bits. BooleanUtils Methods for working with boolean values—in particular, operations for con- verting values to and from boolean values. For example, this: boolean isOk = true; String result; Iverson_ch10.qxd 1/17/05 2:41 PM Page 129 Base Lang Classes 129 if(isOk) result = "ready"; else result = "not ready"; . . . can be replaced simply with: String result = BooleanUtils.toString(isOk, "ready", "not ready"); Generally speaking, BooleanUtils can be grouped into a set of methods to con- vert values to Boolean or boolean or from a boolean/Boolean to integers or String objects. Additional methods are provided specifically for converting strings such as "on," "off," "true," "false," "yes," and "no" to and from boolean/Boolean values. Finally, xor methods are provided for Boolean/boolean arrays. CharRange, CharSet, and CharSetUtils A CharRange represents a contiguous range of characters. The CharSet class uses the CharRange class to express various ASCII ranges such as alphabetic and numeric characters. For character sets that happen to afford logical sorting of characters into ranges (such as ASCII), these classes provide helpful containment checks. The full range of Unicode characters supported by Java is much larger than ASCII, however, and so many applications will likely need to describe their own CharRange sets, perhaps in conjunction with the data available from the java.lang.Character. You can use CharRange and CharSet values (either the predefined values or custom values) in conjunction with the CharSetUtils class to perform certain useful operations, such as counting the number of characters, deleting charac- ters present in a String based on sets passed in, or even squeezing repeated characters as shown: String in = "abc123def"; String chars = CharSetUtils.delete(in, CharSet.ASCII_NUMERIC .toString()); String nums = CharSetUtils.keep(in, CharSet.ASCII_NUMERIC .toString()); System.out.println(chars); // prints abcdef System.out.println(nums); // prints 123 String extras = "bookkeeping"; extras = CharSetUtils.squeeze(extras, CharSet.ASCII_ALPHA .toString()); System.out.println(extras); // prints bokeping Iverson_ch10.qxd 1/17/05 2:41 PM Page 130 130 Lang Chapter 10 ClassUtils In addition to BeanUtils, the Lang ClassUtils package provides additional functionality for working with classes. The utilities in this package do not use the functionality in the java.lang.reflect.* package—they use only the infor- mation available directly from java.lang.Class and where possible from the class name (for example, the class name string is parsed to retrieve package information in lieu of reflection). The methods convertClassesToClassNames and convertClassNamesToClasses convert a List of classes to class names and back. The methods getAllInterfaces and getAllSuperclasses return List objects. Although it’s hard to think of a relevant situation for applications other than development tools, an isInnerClass method is provided. Several different signatures are provided to getPackageName and getShortClassName. Perhaps one of the most useful is the isAssignable method, allowing you to check if you can cast a value before actually performing the operation (which is useful if you want to check if an assignment is valid without incurring the risk of a ClassCastException). ObjectUtils and ObjectUtils.Null The ObjectUtils class principally provides extra semantic control over null values. For example, defaultIfNull, equals, and toString implementations all handle null values gracefully. The appendIdentityToString allows you to retrieve the identity value normally returned by the Object.toString imple- mentation even if the object has overridden toString. Perhaps the most interesting part of ObjectUtils is the addition of an ObjectUtils.Null class to serve as a placeholder for null in instances when null has an additional meaning. Ironically, the addition of type-safe collections to JDK 1.5 will likely mean that this class is increasingly less useful, which is probably for the best in many situations. RandomStringUtils The various implementations of random in this class allow you to easily create random string values according to a wide range of configurable options. System.out.println(RandomStringUtils.randomAscii(16)); // Prints ]_uKDOL*md):fDTT System.out.println(RandomStringUtils.randomAlphabetic(16)); // Prints ygatjcqBbYbCwVBt System.out.println(RandomStringUtils.randomNumeric(16)); // Prints 6731467475431887 char[] availChars = {'A', 'B', 'C', 'D'}; System.out.println(RandomStringUtils.random(16, availChars)); // Prints ADDADCCCDDDDCCBC Iverson_ch10.qxd 1/17/05 2:41 PM Page 131 Base Lang Classes 131 Note that an additional RandomUtils package is provided in the Lang math package, which is described later. SerializationUtils This class provides a few methods to assist with the use of Java serialization. The functionality available includes a generic deep clone operation, allowing a graph of objects to be serialized with a single method call. In addition, seriali- zation and deserialization methods are provided, which wrap the various exceptions as well as the closing of the stream. StringEscapeUtils This class is perhaps one of the most immediately useful for many web appli- cations. Routines are provided to escape and unescape strings for Java, JavaScript, HTML, XML, and SQL. This is useful to guard against attempts by unscrupulous users to inject code into your application (for example, JavaScript in a bit of text to be displayed on a web page, or even an attempt to inject SQL into a form in an attempt to hijack a database). Here is a comparison of the various escape routines in action: String HTML = "$ to \u00A3 Rate"; String Java = "\"It's on my \t tab\""; String SQL = "Ain't bad"; // Original values System.out.println(HTML); System.out.println(Java); System.out.println(SQL); System.out.println(); // Conversion examples System.out.println(StringEscapeUtils.escapeHtml(HTML)); System.out.println(StringEscapeUtils.escapeXml(HTML)); System.out.println(StringEscapeUtils.escapeJava(Java)); System.out.println(StringEscapeUtils.escapeJavaScript(Java)); System.out.println(StringEscapeUtils.escapeSql(SQL)); . . . produces the output: $ to £ Rate "It's on my tab" Ain't bad <B>$ to £ Rate</B> <B>$ to £ Rate</B> \"It's on my \t tab\" \"It\'s on my \t tab\" Ain''t bad Iverson_ch10.qxd 1/17/05 2:41 PM Page 132 132 Lang Chapter 10 StringUtils The StringUtils class contains a variety of null-safe miscellaneous methods. All of the methods will gracefully handle null values, simply returning null if null is passed as an argument. isAlpha isBlank isEmpty isNumeric isWhitespace contains containsOnly containsNone equals indexOf indexOfAny indexOfAnyBut lastIndexOf lastIndexOfAny lastIndexOfAnyBut countMatches left mid right substring substringAfter substringBefore substringBetween trim center leftPad repeat rightPad strip split join The various is methods check if the entire String evaluates to true for the mentioned condition. The contains methods check against a set of characters passed as an argument. Various methods to search Strings. Methods to trim Strings in various ways. Methods that assist the presentation of Strings, particularly useful for console applications. split serves as a more convenient wrapper to the StringTokenizer. join serves as an easy way to fuse an array or Iterator into a single String. Iverson_ch10.qxd 1/17/05 2:41 PM Page 133 Base Lang Classes 133 replace replaceChars replaceOnce delete overlay uppercase lowerCase swapCase capitalize uncapitalize defaultString chomp chop reverse reverseDelimited difference abbreviate Manipulate one String with another. Manipulate the case of a String. Wrapper to automatically protect against null values. chomp removes the last bit of new line information from a String. chop removes the last character of a String. Reverse a String. Returns the differing characters between two String objects. Abbreviates a String, terminating with an ellipsis if necessary. getLevensteinDistance Number of changes needed to change one String into another. Most of these methods are self-explanatory. The getLevensteinDistance is per- haps the most unusual—it calculates the number of changes need to convert a String from one value to another. Below are examples of the use of the two most interesting methods: String longLine = "This is a long bit of text."; System.out.println(StringUtils.abbreviate(longLine, 15)); System.out.println(StringUtils.abbreviate(longLine, 100)); String start = "time"; String end = "fine"; System.out.println(StringUtils.getLevensteinDistance(start, end)); This code produces the following output: This is a lo... This is a long bit of text. 2 Iverson_ch10.qxd 1/17/05 2:41 PM Page 134 134 Lang Chapter 10 SystemUtils The SystemUtils class provides two basic bits of functionality—a set of static variable values corresponding to the various standard system properties, such as file.encoding, file.separator, java.class.path, etc., and a suite of boolean values corresponding to a wide variety of possible platform checks a user might want to perform (e.g., IS_OS_MAC_OSX). An additional version check method is provided to detect the Java ver- sion, allowing for easy basic system conformance checks. For example: System.out.println(SystemUtils.isJavaVersionAtLeast(1.3f)); . . . returns the value true on a JDK 1.4 system. Validate Validation essentially serves as a mechanism for evaluating conditions and throwing an exception if the condition is not true. Most significantly, the vari- ous assertions will generate exceptions and will run on a variety of platforms. Validate.isTrue( i > 0, "The value must be greater than zero: ", i); Validate.notNull( surname, "The surname must not be null"); A suite of static methods is used to assert that values and expressions evalu- ate to true; otherwise an exception is thrown. An advantage of the Validate class is that it allows you to easily set a message string on the thrown excep- tion. This makes Validate more useful for validating user-generated data, as opposed to developer-managed interactions. On JDK 1.4 or later systems, for development-level contracts, you may want to use assertions instead. For more information, see http://java.sun.com/ j2se/1.4.2/docs/guide/lang/assert.html. If you have adopted JUnit (http:// www.junit.org/) as a test framework, you may want to use that assertion facility instead (http://www.junit.org/junit/javadoc/3.8.1/junit/framework/ Assert.html). WordUtils The WordUtils class in many ways serves as an extension of the already large StringUtils class. It works with whitespace-delimited words, mainly perform- ing various capitalization operations. The capitalize method works only on the first letter of each word, whereas the capitalizeFully method works on all of the alphabetical characters. The uncapitalize method only works on a single character (there is no unCapitalizeFully method). This class also offers a wrap function, useful for console applications. For example, the code: String sample = "this is a GREAT System! "; System.out.println(WordUtils.capitalize(sample)); System.out.println(WordUtils.capitalizeFully(sample)); Iverson_ch10.qxd 1/17/05 2:41 PM Page 135 Builder 135 System.out.println(WordUtils.uncapitalize(sample)); System.out.println(WordUtils.swapCase(sample)); sample = sample + sample + sample + sample + sample; System.out.println(WordUtils.wrap(sample, 45)); . . . produces the result: This Is A GREAT System! This Is A Great System! this is a gREAT system! THIS IS A great sYSTEM! this is a GREAT System! this is a GREAT System! this is a GREAT System! this is a GREAT System! this is a GREAT System! BUILDER Perhaps slightly misnamed, this package assists in the creation of Object.equals, Object.toString, Object.hashCode, and Comparable.compareTo methods. Generally speaking, each class (CompareToBuilder, EqualsBuilder, HashCodeBuilder, ReflectionToStringBuilder, and ToStringBuilder) allows you to construct an implementation via either select properties or via a reflection- based comparison. They can be used to quickly construct implementations. The StandardToStringStyle and ToStringStyle classes can be used to cre- ate formatting rules, which can then be used to control the output of the new toString implementation. For example, the code: Object foo = new Object() { public String[] arrayExample = { "One", "Two", "Three"}; public String foo = "sample"; public String toString() { return new ReflectionToStringBuilder(this).toString(); } }; System.out.println(foo.toString()); . . . produces the output: com.cascadetg.ch10.StringExample$1@1a8c4e7[arrayExample={One,Two,Three}, foo=sample] Iverson_ch10.qxd 1/17/05 2:41 PM Page 136 136 ENUM Lang Chapter 10 The Enum package provides additional support for strongly typed enumera- tions. The package requires you to create a subclass of Enum, which then allows you to use the EnumUtils class to interrogate the Enum implementation. Unfortunately, to implement an Enum, several supporting methods must be included. Although a classic C-style enum is a useful pattern, in practice it’s hard to imagine using this Enum package. If you are able to use Java 2 5.0 (also known as JDK 1.5), you can use the built-in enum support as described at http://java.sun.com/j2se/1.5.0/docs/ guide/language/enums.html. EXCEPTION The Exception package provides support for JDK 1.4-style nested Exceptions on pre-JDK 1.4 systems. MATH The class Range and subclasses DoubleRange, FloatRange, IntRange, LongRange, and NumberRange are used to store inclusive ranges of numbers. These range classes can be interrogated for containment, minimums, and maximums. The Fraction class allows you to work with fractions accurately. Fractions are stored as you might write them. For example, the code: Fraction myFraction = Fraction.getFraction(2, 3, 5); System.out.println(myFraction.floatValue()); Fraction secondFraction = Fraction.getFraction(1, 1, 3); System.out.println(secondFraction.floatValue()); myFraction = myFraction.add(secondFraction); System.out.println(myFraction.floatValue()); System.out.print(myFraction.getProperWhole() + " "); System.out.print(myFraction.getProperNumerator() + "/"); System.out.println(myFraction.getDenominator()); . . . outputs the values: 2.6 1.3333334 3.9333334 3 14/15 Iverson_ch10.qxd 1/17/05 2:41 PM Page 137 Summary 137 Note that the float values are represented by a rounded-off value, whereas the Fraction is stored precisely. The Fraction class allows you to parse a string in the standard format X Y/Z (such as 3 14/15) into a Fraction. The JVMRandom and RandomUtils classes provide wrappers to return vari- ous primitive values from the Math.random method. RandomUtils caches the Random object, with each method returning a new value from the same system- wide seed, whereas multiple JVMRandom objects can be created if multiple ran- dom number seeds are desired. The NumberUtils class provides static constants for various 0 and 1 val- ues, utility checks to verify that a String is actually a number, max and min checks for a wide variety of types including arrays, and methods to automati- cally convert strings directly to int values. TIME The Time package has four classes: DateFormatUtils, DateUtils, FastDateFormat, and StopWatch. Both DateFormatUtils and FastDateFormat serve to make it eas- ier to render dates into strings. FastDateFormat is a quick, thread-safe imple- mentation of a date and time formatter. DateFormatUtils includes several FastDateFormat objects, preconfigured for different uses, including different ISO8601 formats as well as an SMTP format. The StopWatch class allows you to perform timings much like a stop- watch—it allows you to start a timer, perform a split, stop, reset, and so on. Note that the StopWatch class is really only a holder for time values from System.currentTimeMillis()—there is no notion of a scheduler or execution thread. Interestingly, the code: StopWatch testWatch = new StopWatch(); try { testWatch.start(); Thread.sleep(1000); testWatch.stop(); System.out.println(testWatch.getTime()); } catch (Exception e) { e.printStackTrace(); } . . . returns a value of 1001. SUMMARY Although the Lang package offers a wide suite of packages, it can be hard to keep track of the various capabilities. This chapter provides an overview, but for more detail on the base classes and the time package, see Appendix A. Iverson_ch10.qxd 1/17/05 2:41 PM Page 138 138 Lang Chapter 10 Almost every Java application can benefit from the Lang package. Similarly, many programs can benefit from the Collections package, described in the next chapter. Project Ideas Write a Swing user interface to wrap the conversion capabilities of StringEscapeUtils. Compare this with writing a command-line interface for the same capabilities, perhaps using the CLI package described in Chapter 13, "CLI (Command Line Interface)." What are the tradeoffs of this approach? Create a clock application using the various date and time formats as described in the Time package. Iverson_ch11.qxd 1/17/05 2:41 PM Page 139 C H A P T E R 11 Collections The term "collections" refers to the notion of objects that contain or manage other objects. Most developers are familiar with the basic collections, including the classic array (such as String[]) or the built-in Java classes (such as java.util.Hashtable). The introduction of a rich Java Collections Framework in Java 2 (JDK 1.2) brought a standardized implementation of classes for expressing more complex relationships. The Apache Jakarta Commons Collections project adds even more capability, as described in this chapter. Table 11-1 compares some of the key differences between basic collection types. When possible, you should try to rely on the interfaces shown, not on the underlying implementation. For example, even if you have marked a HashMap as typed, sorted, and unmodifiable, you should still interface with it as a java.util.Map whenever possible: java.util.Map myMap = new java.util.HashMap(); For more information on the built-in JDK 1.4 collections, see http://java.sun .com/j2se/1.4.2/docs/guide/collections/reference.html. Note this chapter does not duplicate information included in the default JDK documentation—for example, the Stack and SortedMap interfaces are concepts covered as part of the standard Java collection interface. that Table 11-1 Collection Features Array Bag Interface Duplicates Keys Yes Object[] org.apache.commons Yes .collections.Bag No No Indexed Ordered Yes No Yes No List Map Primitive Array Set java.util.List java.util.Map primitive[] java.util.Set Yes No Yes No No Yes No No Yes No Yes No Yes Optional Yes Optional 139 Iverson_ch11.qxd 1/17/05 2:41 PM Page 140 140 Collections Chapter 11 The meaning of each column heading in Table 11-1 is as follows: ☞ Interface: The expected Java interface for this collection type. ☞ Duplicates: Are duplicate elements allowed? ☞ Keys: Are elements accessible by a key value (e.g., java.util.Hashtable)? ☞ Indexed: Is the order of the elements maintained by a column in the database? ☞ Ordered: Are the results returned as a sorted collection? COLLECTIONS CONCEPTS It can be difficult to get a handle on the Collections package due to the sheer number of classes and interfaces provided (as shown in Figure 11-1), some of which are new or unfamiliar to many Java developers. Despite this initial over- whelming complexity, these classes can be broken down into several core con- cepts, each of which is presented in this chapter. The various utility classes are used to help generate the appropriate combinations of various items. For exam- ple, a typed, sorted bag can be returned from the appropriate static BagUtils. Generating Output The various examples in this chapter make use of a method echo(). This method is simply a utility method that writes the contents of the collection to System.out. Bag A Bag is an unordered collection that may contain duplicate elements. The Bag maintains counts for the duplicate items, managing each count and perform- ing operations against this count. The Commons Bag hierarchy is shown in Figure 11-2. For example, imagine a Bag containing the objects a, a, b, and c. Calling getCount(Object) passing in the a object would return 2. Calling uniqueSet() would return a, b, and c. This is an important consideration with the Bag inter- face, as multiple calls to add an object will increment that object count. The remove(Object) method removes the object completely from the Bag, regardless of the current count. To decrement the count, remove(Object, int) is used, with the second parameter indicating the number of items to be removed. For example, the code: org.apache.commons.collections.Bag myBag = new org.apache.commons.collections.bag.HashBag(); myBag.add("Test1", 3); myBag.add("Test2"); Iverson_ch11.qxd 1/17/05 2:41 PM Page 141 d e s p a l l o c t e S t c a r t s b A n o i t c e l l o C d e d n u o B s e u l a V t e S y r t n E d e s p a l l o c d e s p a l l o c d e s p a l l o c r e f f u B o f i F r e d n u o B d e s p a l l o c d e s p a l l o c w e i V n o i t c e l l o C » e c n e r e e r « f » e c a f r e t n « i r e f f u B o f i F d e d n u o b n U d e s p a l l o c d e s p a l l o c » e c n e r e f e r « t s i L y a r r A p a M n a e B d e s p a l l o c d e s p a l l o c p a e H y r a n B i k c a t S y a r r A d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c t s i L y a r r A t s a F d e s p a l l o c d e s p a l l o c p a M e c n e r e f e R d e s p a l l o c d e s p a l l o c » e c n e r e e r « f » e c a f r e t i n « l e b a z i l a n r e t x E p a M d e r e d r O e b u o D l d e s p a l l o c d e s p a l l o c g a B p a M t l u a f e D » e c a t f r e n « i d e s p a l l o c d e s p a l l o c g a B d e t r o S d e s p a l l o c g a B h s a H d e s p a l l o c g a B e e r T d e s p a l l o c » e c n e r e e r « f » e c a f r e t n « i t e S » e c a f r e t n « i r e f f u B d e s p a l l o c » e c n e r e f e r « » e c a f r e t n « i e l b a e n o C l » e c n e r e f e r « p a M t c a r t s b A » e c a f r e t i n « g a B d e s p a l l o c p a M e e r T t s a F p a M h s a H t s a F d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c » e c n e r e f e r « » e c n e r e f e r « p a M e e r T p a M h s a H » e c n e r e f e r « » e c a f r e t n « i e l b a z i l a i r e S t e S y e K d e s p a l l o c » e c n e r e f e r « n o i t c e l l o C t c a r t s b A » e c n e r e f e r « » e c a f r e t n « i » e c a f r e t n « i e u e u Q y t i r o i r P d e s p a l l o c p a M U R L d e s p a l l o c d e s p a l l o c » e c n e r e e r « f » e c a f r e t i n « p a M t s i L y t i r o i r P d e z i n o r h c n y S e u e u Q d e s p a l l o c d e s p a l l o c p a M h s a H d e c n e u q e S d e s p a l l o c d e s p a l l o c p a M e l b a r e t I d e s p a l l o c d e s p a l l o c d e s p a l l o c » e c a f r e t n « i p a M t e k c u B c i t a t S p a M y x o r P d e s p a l l o c d e s p a l l o c i d e k n L e l b a r o s r u C t s i L d e s p a l l o c d e s p a l l o c t s i L b u S d e s p a l l o c d e s p a l l o c » e c a f r e t n « i r e m r o f s n a r T d e s p a l l o c e l b a t s i L d e s p a l l o c d e s p a l l o c t s i L b u S e l b a r o s r u C d e s p a l l o c d e s p a l l o c » e c a f r e t n « i e r u s o C l d e s p a l l o c p a M d e t r o S p a M d e r e d r O p a M d B i i » e c n e r e f e r « » e c a f r e t n « i » e c a f r e t i n « » e c a f r e t n « i » e c a f r e t n « i d e s p a l l o c d e s p a l l o c i i p a M d B d e t r o S i i p a M d B d e r e d r O d e s p a l l o c d e s p a l l o c » e c a f r e t i n « p a M i t l u M d e s p a l l o c » e c a f r e t i n « p a M d e d n u o B d e s p a l l o c 141 . w e i v r e v o s s a l c n o i t c e l l o C 1 - 1 1 e r u g F i Iverson_ch11.qxd 1/17/05 2:41 PM Page 142 142 Collections Chapter 11 echo(myBag); System.out.println(); myBag.remove("Test1"); echo(myBag); . . . produces the output: Test2 Test1 Test1 Test1 Test2 Warning: The Bag interface changes the interpretation of the Collection methods. This change in behavior can be a rude shock if you are not precisely familiar with the changes. Although changed methods are marked in the javadoc as being in violation, the changes are all related to the notion of Bag’s count tracking behavior. Note that some of the following classes are not actually subclasses but are instead intended to serve as wrappers for a Bag to add additional behavior. For example, the TypedBag class allows you to add type checking to a Bag. Related Classes: AbstractBagDecorator, AbstractMapBag, AbstractSortedBagDecorator, Bag BagUtils, DefaultMapBag, HashBag, PredicatedBag, PredicatedSortedBag, SortedBag, SynchronizedBag, SynchronizedSortedBag, TransformedBag, TransformedSortedBag, TreeBag, TypedBag, TypedSortedBag, UnmodifiableBag, UnmodifiableSortedBag Bean The BeanMap class allows you to wrap and present a JavaBean as a java.util.Map. The various properties of the JavaBean are treated as keys, with the property values exposed as Map properties. For more information on JavaBeans, see BeanUtils. For example, the code: java.awt.Button myButton = new java.awt.Button(); java.util.Map myMap = new org.apache.commons.collections.BeanMap( myButton); myMap.put("label", "hello"); Iverson_ch11.qxd 1/17/05 2:41 PM Page 143 . s e s s a l c g a B 2 - 1 1 e r u g F i 143 Iverson_ch11.qxd 1/17/05 2:41 PM Page 144 144 Collections Chapter 11 java.util.Set myKeys = myMap.keySet(); System.out.println("Keys:"); echo(myKeys); System.out.println(); System.out.println("Values:"); echo(myMap.values()); . . . produces the output: Keys: accessibleContext focusable actionListeners label enabled actionCommand visible background name foreground font Values: java.awt.Button$AccessibleAWTButton@17fa65e true [Ljava.awt.event.ActionListener;@18385e3 hello true hello true null button0 null null Related Classes: BeanMap BidiMap The BidiMap classes allow for bidirectional use of map. The default Map inter- face allows you to retrieve a value from a map with the key, but not the other way around (it is necessary to iterate through the keys and values to identify the value from the key, unless there is some other contract in play). The Commons BidiMap hierarchy is shown in Figure 11-3. The code: org.apache.commons.collections.BidiMap myBidiMap = new org.apache.commons.collections.bidimap.TreeBidiMap(); myBidiMap.put("Example", "1"); myBidiMap.put("Another", "2"); Iverson_ch11.qxd 1/17/05 2:41 PM Page 145 Collections Concepts 145 // Note easy (and fast) access to key from value System.out.println(myBidiMap.getKey("1")); System.out.println(myBidiMap.get("Another")); echo(myBidiMap); System.out.println("Notice the now missing Example key:"); myBidiMap.put("Another", "1"); echo(myBidiMap); . . . produces the output: Example 2 Another=2 Example=1 Notice the now missing Example key: Another=1 Warning: BidiMap enforces a strict 1:1 relationship between the keys and values. If one side of the key/value pair exists when a new key/value pair is added, the existing key/value pair will be removed. For example, if an A/B key/value pair exists, adding either A/C or C/B will cause the A/B value pair to be removed. Related Classes: AbstractBidiMapDecorator, AbstractDualBidiMap, AbstractOrderedBidiMapDecorator, AbstractSortedBidiMapDecorator, BidiMap, DualHashBidiMap, DualTreeBidiMap, OrderedBidiMap, SortedBidiMap, TreeBidiMap, UnmodifiableBidiMap, UnmodifiableOrderedBidiMap, UnmodifiableSortedBidiMap Blocking Used to decorate another Buffer class to make the get() and remove() methods block if the Buffer is empty. Note that this class extends SynchronizedBuffer and is thread-safe. Related Classes: BlockingBuffer Bounded The various Bounded collections are used to indicate that a maximum number of elements are allowed in the collection. An exception is thrown if an attempt is made to add an element to a full collection. Iverson_ch11.qxd 1/17/05 2:41 PM Page 146 . s e s s a l c p a M i d i B 3 - 1 1 e r u g F i 146 Iverson_ch11.qxd 1/17/05 2:41 PM Page 147 Collections Concepts 147 The code: java.util.Map myMap = new java.util.HashMap(); myMap.put("One", "1"); myMap.put("Two", "2"); myMap.put("Three", "3"); myMap = org.apache.commons.collections.map.FixedSizeMap .decorate(myMap); try { myMap.put("Four", "4"); } catch (Exception e) { System.out.println(e.getMessage()); } . . . produces the output: Cannot put new key/value pair - Map is fixed size Related Classes: BoundedCollection, BoundedFifoBuffer, BoundedMap, UnmodifiableBoundedCollection Buffer A buffer is used to describe a collection that expects to remove objects in a spe- cific order. Last-in-first-out (LIFO) buffer (ArrayStack), first-in-first-out (FIFO) buffer (UnboundedFifoBuffer), and java.util.Comparator-based (PriorityBuffer) implementations are provided, among others. The Commons Buffer hierarchy is shown in Figure 11-4. Related Classes: AbstractBufferDecorator, BlockingBuffer, BoundedFifoBuffer, BoundedFifoBuffer, Buffer, BufferOverflowException, BufferUnderflowException, BufferUtils, CircularFifoBuffer, PredicatedBuffer, PriorityBuffer, SynchronizedBuffer, TransformedBuffer, TypedBuffer, UnboundedFifoBuffer, UnboundedFifoBuffer, UnmodifiableBuffer Circular CircularFifoBuffer is a first-in-first-out buffer with a fixed size that replaces the least recently added element if full. It is both a bounded collection and a buffer. Related Classes: CircularFifoBuffer Closure A closure simply provides a simple interface with a single void execute(java.lang.Object input) method. The only failure signal is a thrown exception, implying that a closure method is not expected to fail. A closure is useful in conjunction with a transformer. Iverson_ch11.qxd 1/17/05 2:41 PM Page 148 . s e s s a l c r e f f u B 4 - 1 1 e r u g F i 148 Iverson_ch11.qxd 1/17/05 2:41 PM Page 149 Collections Concepts 149 See the Functor entry for more information. For example, the code: org.apache.commons.collections.Closure myEchoClosure = new org.apache.commons.collections.Closure() { public void execute(Object in) { System.out.println(in.toString()); } }; org.apache.commons.collections.Closure mySizeClosure = new org.apache.commons.collections.Closure() { public void execute(Object in) { System.out.println(in.toString() .length()); } }; java.util.Map myMap = new java.util.HashMap(); myMap = org.apache.commons.collections.map.TransformedMap .decorate( myMap, org.apache.commons.collections.functors.ClosureTransformer .getInstance(myEchoClosure), org.apache.commons.collections.functors.ClosureTransformer .getInstance(mySizeClosure)); myMap.put("Hello", "World"); myMap.put("Apple", "Orange"); myMap.put("One", "Example of a String"); . . . generates the output: Hello 5 Apple 6 One 19 You’ll notice in this example that the closures are used to echo values when elements are added to the Map. The first closure writes the value of the object to System.out, and the second closure writes the length of the String representation. Related Classes: ChainedClosure, Closure, ClosureTransformer, ClosureUtils, ExceptionClosure, ForClosure, IfClosure, NOPClosure, SwitchClosure, TransformerClosure, WhileClosure Iverson_ch11.qxd 1/17/05 2:41 PM Page 150 150 Collections Chapter 11 Collating A CollatingIterator can be used to sort an Iterator according to a particular Comparator. Even more powerful, a CollatingIterator can seamlessly weave together two or more Iterators as a single Iterator using the comparator provided. The code: java.util.SortedMap myMap = new java.util.TreeMap(); myMap.put("Hello", "World"); myMap.put("Apple", "Orange"); myMap.put("One", "Example of a String"); java.util.SortedSet mySet = new java.util.TreeSet(); mySet.add("Example"); mySet.add("Bingo"); org.apache.commons.collections.iterators.CollatingIterator myIterator = new org.apache.commons.collections.iterators.CollatingIterator(); myIterator.setComparator(java.text.Collator .getInstance()); myIterator.addIterator(myMap.keySet() .iterator()); myIterator.addIterator(mySet.iterator()); while (myIterator.hasNext()) System.out.println(myIterator.next()); . . . produces the output: Apple Bingo Example Hello One Note that the iterators supplied to the CollatingIterator are already sorted. Although CollatingIterator can be used to weave together an arbitrary num- ber of iterators into a single iterator, it will only produce properly sorted results if the supplied iterators are already sorted. Related Classes: CollatingIterator Comparator The built-in JDK comparator functionality is used to provide a relative order for two objects. This order is given an integer value. For example, the order between "A" and "D" might be expressed as 3, and "D" and "A" as -3. The Collections package makes heavy use of the Comparator interface, and it pro- vides a rich set of additional comparators, including comparators for handling null values, reversing a comparator, and chaining comparators (for example, combining the natural comparator with the null comparator). Iverson_ch11.qxd 1/17/05 2:41 PM Page 151 Collections Concepts 151 Related Classes: BooleanComparator, ComparableComparator, ComparatorChain, ComparatorUtils, FixedOrderComparator, NullComparator, ReverseComparator, TransformingComparator Composite This allows you to join a set of collections and provide them as a single, unified view. For example, given a map of cats and a map of dogs, you may want to present them as a single map. Changes to objects may be performed directly, but add and remove operations require the use of a custom CompositeCollection.CollectionMutator implementation to determine which collection will actually remove or add the object. Related Classes: CompositeCollection, CompositeMap, CompositeSet Cursorable Typically, changes to the owning collection are not possible from an iterator. The CursorableLinkedList class provides an exception to this rule—modifications the to CursorableLinkedList is operated on from a single thread, you can make modi- fications from either the owning collection or the iterator as needed. collection are possible iterator. As from the long as the For example: org.apache.commons.collections.list.CursorableLinkedList myList = new org.apache.commons.collections.list.CursorableLinkedList(); myList.add("1 (original)"); myList.add("2 (original)"); myList.add("3 (original)"); myList.add("4 (original)"); myList.add("5 (original)"); myList.add("6 (original)"); java.util.ListIterator myIterator = myList .listIterator(); while (myIterator.hasNext()) { System.out.println(myIterator.next()); int nextIndexValue = myIterator .nextIndex(); if (nextIndexValue < 5) myList.add((myList.size() + 1) + " (added)"); } . . . produces the output: 1 (original) 2 (original) 3 (original) Iverson_ch11.qxd 1/17/05 2:41 PM Page 152 152 Collections Chapter 11 4 (original) 5 (original) 6 (original) 7 (added) 8 (added) 9 (added) 10 (added) Notice that changes made to the list while processing the iterator actually cause the iterator to update. Related Classes: CursorableLinkedList Factory This is an interface corresponding to the popular design pattern. Default Factory implementations are provided for a variety of scenarios, including no- arg constructor classes, or even a factory for objects with a specific constructor and set of arguments. Factory implementations are useful in conjunction with Lazy collections. Related Classes: ConstantFactory, ExceptionFactory, Factory, FactoryTransformer, FactoryUtils, InstantiateFactory, PrototypeFactory Fast The various Fast classes are intended for use in multi-threaded environments in which the vast majority of the access is intended to be read-only. After a col- lection is created and the data is added, calling setFast(true) puts the collec- tion in a high performance mode. There is no advantage to using a "Fast" implementation on a single thread. If you have a Map that is expected to have three or fewer elements and performance is a consideration, you may want to consider the Flat3Map implementation. Related Classes: FastArrayList, FastHashMap, FastTreeMap Fifo Describes a first-in-first-out buffer. See Buffer for more information. Related Classes: BoundedFifoBuffer, BoundedFifoBuffer, CircularFifoBuffer, UnboundedFifoBuffer, UnboundedFifoBuffer FixedSize Allows you to decorate a given collection to indicate that the size of the col- lection is fixed—any attempt to add or remove an element is prohibited. An element may be replaced, however (as this would not change the size of the collection). Iverson_ch11.qxd 1/17/05 2:41 PM Page 153 Collections Concepts 153 Related Classes: FixedOrderComparator, FixedSizeList, FixedSizeMap, FixedSizeSortedMap Flat3 Describes a Map highly optimized for read/write access when less than three elements are present. When more than three elements are present, this class defaults to the HashMap implementation, with a slight penalty for the extra methods. Related Classes: Flat3Map Functor Functors describe a set of interfaces defining a single operation. For example, a closure simply provides an execute method, a predicate provides a function for boolean evaluation, a transformer provides a single method to produce an object given an object, and a factory provides a single method for creating a new object. Closures and predicates are only useful in conjunction with other classes, in particular a transformer. Custom functors are often passed as anonymous inner objects. When combined with the functors provided by the Collections package, complex operations can be wrapped and handled in con- junction with a collection. See Closure, Predicate, Transformer, and Factory for more information. Hash All Java objects extend java.lang.Object, which defines a method int hashCode(). This hash code is used by various hash implementations as values for optimizing access. For a more detailed explanation of the meaning and use of a hash-based collection, see http://www.linuxgazette.com/issue57/tindale .html. Note that the various hash collections rely on a "good" value to be returned by the hashCode() function. The org.apache.commons.lang.builder .HashCodeBuilder, part of the Lang package, can assist in creating hashCode() implementations. Related Classes: AbstractHashedMap, DualHashBidiMap, FastHashMap, HashBag, HashedMap, MultiHashMap, SequencedHashMap Identity Most collections use the Object.equals() method to determine if two objects are equal. The identity classes use the == operation to determine equality instead. The == operation compares the object reference identity of two objects. Two objects created independently with identical data may or may not have the same object reference identity, depending on the situation and compiler. Iverson_ch11.qxd 1/17/05 2:41 PM Page 154 154 Collections Chapter 11 Generally speaking, the == operation is useful for lower-level object compar- isons more concerned with the underlying thread, compiler, and class loader, whereas the equals() method is useful for business operations. Related Classes: IdentityMap, IdentityPredicate, ReferenceIdentityMap Lazy The Lazy classes allow you to decorate a collection, defining factories that will be used to automatically create objects when a null value would otherwise be returned. For example, if the tenth element of a lazy list with a size of six was requested, the lazy list would grow the size of the list to ten, create a new object at the tenth slot, and return the new object. For example, the code: org.apache.commons.collections.Factory factory = new org.apache.commons.collections.Factory() { public Object create() { return new java.util.Date(); } }; java.util.Map lazy = org.apache.commons.collections.map.LazyMap .decorate(new java.util.HashMap(), factory); String current = lazy.get("NOW").toString(); String second = lazy.get("SECOND").toString(); System.out.println(lazy.size()); . . . outputs the value 2. Related Classes: LazyList, LazyMap, LazySortedMap Linked A linked list simply provides bidirectional access to a list, allowing for easy retrieval of objects in either order. Related Classes: AbstractLinkedList, AbstractLinkedMap, CursorableLinkedList, CursorableLinkedList, LinkedMap, NodeCachingLinkedList List This is an ordered collection (also known as a sequence). The user of this inter- face has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list) and search for elements in the list. A list is the next step up from a simple array. A Iverson_ch11.qxd 1/17/05 2:41 PM Page 155 Collections Concepts 155 Figure 11-5 List classes. list is particularly useful in conjunction with a transformer. The Commons List hierarchy is shown in Figure 11-5. Related Classes: AbstractLinkedList, AbstractListDecorator, AbstractListIteratorDecorator, AbstractSerializableListDecorator, ArrayListIterator, CursorableLinkedList, CursorableLinkedList, EmptyListIterator, FastArrayList, FilterListIterator, FixedSizeList, Iverson_ch11.qxd 1/17/05 2:41 PM Page 156 156 Collections Chapter 11 LazyList, ListIteratorWrapper, ListOrderedMap ListOrderedSet, ListUtils, NodeCachingLinkedList, ObjectArrayListIterator, PredicatedList ProxyListIterator, ResettableListIterator, SetUniqueList, SingletonListIterator, SynchronizedList, TransformedList, TreeList, TypedList, UnmodifiableList, UnmodifiableListIterator LRU Refers to the notion that the fixed size map maintains a notion of the fre- quency of use, removing the "least recently used" entry when the map is full and a new entry is submitted. Only the put and get operations affect the track- ing of items—iteration and queries to verify the presence of a key or value do not affect the map. For example, the code: java.util.Map myMap = new org.apache.commons.collections.map.LRUMap(3); myMap.put("One", "1"); myMap.put("Two", "2"); myMap.put("Three", "3"); myMap.get("One"); myMap.get("Three"); myMap.put("Four", "4"); echo(myMap.keySet()); . . . produces the results: One Three Four Related Classes: LRUMap Map This is an object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value. A sorted map will maintain the keys in order. One of the most popular types of collection, the vast majority of the classes in the Collection package involve maps in one way or another. The Commons Map hierarchy is shown in Figure 11-6. Keep in mind that many of the map classes merely act as decorators for other map instances. For example, the MapUtils.typedSortedMap(java.util .SortedMap map, java.lang.Class keyType, java.lang.Class valueType) method allows you to take an existing HashMap, sort it using a comparator, and apply runtime type-checks to both the keys and values. Iverson_ch11.qxd 1/17/05 2:41 PM Page 157 . s e s s a l c p a M 6 - 1 1 e r u g F i 157 Iverson_ch11.qxd 1/17/05 2:41 PM Page 158 158 Multi Collections Chapter 11 A Multi map is used to track a map of maps. In other words, each element requires two identifying key values. For example, the code: String first = "Will"; String last = "Iverson"; String phone = "(321) 555-1212"; java.util.Map myMap = new java.util.HashMap(); org.apache.commons.collections.keyvalue.MultiKey multiKey = new org.apache.commons.collections.keyvalue.MultiKey( first, last); myMap.put(multiKey, phone); System.out.println(myMap.get(multiKey)); System.out.println(); echo(myMap); . . . produces the result: (321) 555-1212 MultiKey[Will, Iverson]=(321) 555-1212 Related Classes: MultiHashMap, MultiKey, MultiKeyMap, MultiMap NodeCaching By default, a List will use Node objects to maintain the items within. The NodeCachingLinkedList implementation attempts to reuse these Nodes to avoid excessive object creation and garbage collection. It is therefore particularly useful as a long-lived object that expects significant addition and removal of objects over time. Related Classes: NodeCachingLinkedList ObjectGraph Creates a single Iterator to walk down a complex graph of objects. This may be an Iterator that in turn contains an arbitrarily deep number of nested Iterators and objects, or a root object with a custom transformer (which returns either objects or Iterators as appropriate). For example, the code: org.apache.commons.collections.Transformer myTransformer = new org.apache.commons.collections.Transformer() { public Object transform(Object input) Iverson_ch11.qxd 1/17/05 2:41 PM Page 159 Collections Concepts 159 { } }; if (input instanceof java.util.Collection) { return ((java.util.Collection) input) .iterator(); } else return input; java.util.Set firstSet = new java.util.HashSet(); java.util.Set secondSet = new java.util.HashSet(); java.util.Set thirdSet = new java.util.HashSet(); firstSet.add("Orange"); firstSet.add("Apple"); secondSet.add("Radio"); secondSet.add("Television"); thirdSet.add("Fire"); thirdSet.add("Water"); firstSet.add(secondSet); firstSet.add(thirdSet); org.apache.commons.collections.iterators.ObjectGraphIterator myIterator = new org.apache.commons.collections.iterators.ObjectGraphIterator( firstSet, myTransformer); while (myIterator.hasNext()) System.out.println(myIterator.next()); . . . produces the output: Water Fire Apple Radio Television Orange Related Classes: ObjectArrayIterator, ObjectArrayListIterator, ObjectGraphIterator Ordered An ordered collection allows for both forward and backward iteration over the elements in the collection. This includes quick access to the first, last, next, and previous element. Related Classes: AbstractOrderedBidiMapDecorator, AbstractOrderedMapDecorator, AbstractOrderedMapIteratorDecorator, DoubleOrderedMap, EmptyOrderedIterator, EmptyOrderedMapIterator, ListOrderedMap, ListOrderedSet, OrderedBidiMap, OrderedIterator, OrderedMap, OrderedMapIterator, UnmodifiableOrderedBidiMap, UnmodifiableOrderedMap, UnmodifiableOrderedMapIterator Iverson_ch11.qxd 1/17/05 2:41 PM Page 160 160 Collections Chapter 11 Predicate A simple interface used to perform a test—a single method, boolean evaluate(java.lang.Object object). Unlike a closure, it returns true/false. For more information, see Functor. Related Classes: AllPredicate, AndPredicate, AnyPredicate, EqualPredicate, ExceptionPredicate, FalsePredicate, IdentityPredicate, InstanceofPredicate, NonePredicate, NotNullPredicate, NotPredicate, NullIsExceptionPredicate, NullIsFalsePredicate, NullIsTruePredicate, NullPredicate, OnePredicate, OrPredicate, Predicate, PredicatedBag, PredicatedBuffer, PredicatedCollection, PredicateDecorator, PredicatedList, PredicatedMap, PredicatedSet, PredicatedSortedBag, PredicatedSortedMap, PredicatedSortedSet, PredicateTransformer, PredicateUtils, TransformedPredicate, TransformerPredicate, TruePredicate, UniquePredicate Reference The various reference map collections allow you to specify that entries may be removed by the garbage collector. In other words, references from this collec- tion "don’t count" when the Java virtual machine is assessing an object as still being in use for purposes of garbage collection. Related Classes: AbstractReferenceMap, ReferenceIdentityMap, ReferenceMap Set This is a collection that contains no duplicate elements. More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2), and at most one null element. A sorted set will maintain the elements in order. The Commons Map hierarchy is shown in Figure 11-7. Related Classes: AbstractSerializableSetDecorator, AbstractSetDecorator, AbstractSortedSetDecorator, CompositeSet, EntrySetMapIterator, ListOrderedSet, MapBackedSet, PredicatedSet, PredicatedSortedSet, SetUniqueList, SetUtils SynchronizedSet, SynchronizedSortedSet, TransformedSet, TransformedSortedSet, TypedSet, TypedSortedSet, UnmodifiableEntrySet, UnmodifiableSet, UnmodifiableSortedSet Singleton This is a collection that may contain one and only one element. The element may be changed, but no operation that would result in zero or more than one element is allowed. Iverson_ch11.qxd 1/17/05 2:41 PM Page 161 . s e s s a l c t e S 7 - 1 1 e r u g F i 161 Iverson_ch11.qxd 1/17/05 2:41 PM Page 162 162 Collections Chapter 11 Related Classes: SingletonIterator, SingletonListIterator, SingletonMap StaticBucket An efficient, thread-safe Map, designed for situations in which the Map is expected to be accessed frequently by multiple threads. If you expect to only access the put, get, remove, and containsKey methods, this class will dramati- cally reduce thread contentions. Bulk operations, however, are not atomic, meaning that two or more threads operating on the same collection can have indeterminate results. Related Classes: StaticBucketMap Synchronized The various Synchronized collection classes allow you to decorate a collection, providing synchronized implementations of the collection methods, which are then passed along to the underlying collection. Related Classes: SynchronizedBag, SynchronizedBuffer, SynchronizedCollection, SynchronizedList, SynchronizedPriorityQueue, SynchronizedSet, SynchronizedSortedBag, SynchronizedSortedSet Transformed/Transformer The transformed classes allow a transform operation to be performed on objects as they are added to the collection. These classes merely decorate another implementation—they are not intended to serve as standalone implementations. The java.lang.Object transform(java.lang.Object input) method of the Transformer interface is used to perform the operation. Note that the input object is generally expected to be unchanged, and a new output object is generated. For an example of a transformation, see the previous entries on Closure and ObjectGraph. Related Classes: ChainedTransformer, CloneTransformer, ClosureTransformer, ConstantTransformer, ExceptionTransformer, FactoryTransformer, InstantiateTransformer, InvokerTransformer, MapTransformer, NOPTransformer, PredicateTransformer, StringValueTransformer, SwitchTransformer, TransformedBag, TransformedBuffer, TransformedCollection, TransformedList, TransformedMap, TransformedPredicate, TransformedSet, TransformedSortedBag, TransformedSortedMap, TransformedSortedSet, Transformer, TransformerClosure, TransformerPredicate, TransformerUtils, TransformingComparator, TransformIterator Iverson_ch11.qxd 1/17/05 2:41 PM Page 163 Collections Concepts Typed 163 Decorators that allow runtime type checks to be applied to a collection. Note that the addition of generics to Java 5.0 (also known as JDK 1.5) reduces the need for these type wrappers. For more information on generics, see http://java.sun.com/j2se/1.5.0/docs/guide/language/generics.html. For example, the code: java.util.Set mySet = new java.util.HashSet(); mySet = org.apache.commons.collections.set.TypedSet .decorate(mySet, Integer.class); mySet.add(new Integer(5)); mySet.add(new Integer(15)); try { mySet.add(new Long(100000)); } catch (Exception e) { System.out.println(e.getMessage()); } echo(mySet); . . . produces the result: Cannot add Object '100000' - Predicate rejected it 15 5 Related Classes: TypedBag, TypedMap, TypedSet, TypedSortedBag, TypedSortedMap, TypedSortedSet TypedCollection, TypedBuffer, TypedList, Unmodifiable This is a decorator that wraps a collection as unmodifiable. For example, a configuration collection may be initialized at application launch and then shared with a variety of resources over the course of the application’s life cycle, with changes to the configuration object disallowed by decorating the collection as unmodifiable. Related Classes: UnmodifiableBag, UnmodifiableBidiMap, UnmodifiableBoundedCollection, UnmodifiableBuffer, UnmodifiableCollection, UnmodifiableEntrySet, UnmodifiableIterator, UnmodifiableList, UnmodifiableListIterator, UnmodifiableMap, UnmodifiableMapEntry, UnmodifiableMapIterator, UnmodifiableOrderedBidiMap, UnmodifiableOrderedMap, UnmodifiableOrderedMapIterator, UnmodifiableSet, UnmodifiableSortedBag, UnmodifiableSortedBidiMap, UnmodifiableSortedMap, UnmodifiableSortedSet Iverson_ch11.qxd 1/17/05 2:41 PM Page 164 164 SUMMARY Collections Chapter 11 The Collections package provides a broad suite of functionality associated with managing relationships between objects. While many introductions to object-oriented development focus on the design of objects and the class hierarchy, the proper use of relationships to bind objects together is as, if not more, important. Project Ideas What user interfaces are best used to present the various collection types to users? How are these interfaces impacted by the size of the collection? Is this easier or harder in Swing or HTML? Consider applications that you have written using the collection types built in to Java. How hard would it be to add more control to the various collections using the Commons Collections package? Iverson_ch12.qxd 1/17/05 2:42 PM Page 165 C H A P T E R 12 Codec The term codec originates from the words compression/decompression (amus- ingly, the abbreviation is in a sense a form of compression). Popular codecs perform such functions as compressing and decompressing arbitrary data (e.g., ZIP, RAR), image-specific data (e.g., GIF, JPEG), or audio data (e.g., MP3, AIFF). Over time, the term codec has grown to include a wide variety of data translations, not all of which are useful for compression and decompression but instead serve other functions such as security, data transmission, or even spell-checking. While the JDK offers a variety of built-in handlers for dealing with popular compression formats such as ZIP, GIF, and JPG, the Apache Commons Codec project fills in other gaps in functionality. As of this writing, the Codec includes utilities in the following areas: ☞ Data transmission (Base64 and Hex encoding/decoding) ☞ Hash encoding (MD5 and SHA, useful for passwords and file signatures) ☞ Phonetic encoding (useful for features such as spell-checking) In this chapter, we will look at this functionality in a series of methods in a single class. Listing 12-1 shows the header information for the class—note the imports from the Codec package. Listing 12-1 Imports and Class Header package com.cascadetg.ch12; import java.io.FileInputStream; import java.io.UnsupportedEncodingException; import org.apache.commons.codec.binary.Base64; import org.apache.commons.codec.binary.Hex; import org.apache.commons.codec.digest.DigestUtils; import org.apache.commons.codec.language.DoubleMetaphone; import org.apache.commons.codec.language.Metaphone; import org.apache.commons.codec.language.RefinedSoundex; import org.apache.commons.codec.language.Soundex; import org.apache.commons.codec.net.URLCodec; (continues) 165 Iverson_ch12.qxd 1/17/05 2:42 PM Page 166 166 Codec Chapter 12 Listing 12-1 (continued ) // To change the default encoding, use the command // java -Dfile.encoding=UTF8 EncodingDemo // when launching. Keep in mind that if you change the encoding, // you should also change the encoding of the terminal to // match (an option not available on all systems). public class EncodingDemo { public static void printHeader(String title) { System.out.println(); System.out.println("================================"); System.out.println(title); System.out.println("================================"); } public static void main(String[] args) { fileEncodingDemo(); encodingDemo(); phoneticDemo(); hashEncodingDemo(); formURLEncodingDemo(); } ... // Rest of code follows. The imports refer to the various classes of the Codec package, as shown in Figure 12-1. The MD5 and SHA classes aren’t part of the rest of the hierarchy but are instead broken out into a utility class. All of the interfaces provided are intended for use with either String or byte[] parameters, not the more sophis- ticated stream interfaces present in the JDK. This is acceptable for most uses, but it does require the entire data set to be loaded into memory before use. CHARACTER ENCODINGS Let us start by considering basic facts about binary data. Generally speaking, binary data consists of streams of bytes. These bytes have numerical values from 0 to 255, as composed by 8 bits (zeros or ones). The meaning of the bytes depends on the application. Now, compare binary data with character data. At first, most English speakers think of ASCII as character data—an international standard for con- verting byte data (numbers from 0 to 255) to characters. However, ASCII only defines the meaning of the lower 128 values—the remaining 128 possible numbers (also known as high-bit characters) don’t correspond to a specific character. On some systems, these high-bit characters are used to represent locale-specific information. For example, a French system might use high-bit characters to represent French-specific information, whereas an English system might use the high-bit characters to represent special graphics (such as the trademark symbol). Iverson_ch12.qxd 1/17/05 2:42 PM Page 167 d e s p a l l o c d e s p a l l o c d d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c d e s p a l l o c . s e s s a l c c e d o C s n o m m o C e h c a p A 1 - 2 1 e r u g F i 167 Iverson_ch12.qxd 1/17/05 2:42 PM Page 168 168 Codec Chapter 12 As if high-bit characters weren’t complicated enough, many languages have far more than 255 characters. To support these languages, two or even three bytes may be required to store individual characters. Therefore, to prop- erly read and understand the character data represented by a stream of bytes, you must know the proper encoding for the data. In other words, the character encoding is a bit of information that lets your application know how to inter- pret the binary representation of the data as character data. Java uses Unicode, a unified international standard for representing character data, to store character data internally. So, a String in Java repre- sents a series of Unicode bytes. Listing 12-2 shows a bit of code that illustrates the various interpreta- tions of a bit of character data. The string highBitCharacters is used as our test case—this string contains a normal ASCII character and also several Unicode character points, expressed with the \u0000 format, that represent characters not common to all languages. The \u represents a Unicode escape sequence, and the 0000 represents the specific character. Listing 12-2 Encoding Example Source public static void encodingDemo() { // These strings are used to refer to specific // encoding types. String UTF8 = "UTF-8"; String WindowsLatin1 = "Cp1252"; // These characters are, in order, the ordinary ASCII letter X, // a pound sign (the UK currency), a latin capital letter C // with cedilla, a latin small letter e with diaeresis, and // registered sign (typically used to indicate a registered // trademark). These characters are represented internally // in the JVM as Unicode. Their output as bytes is // determined by the default encoding for the system, or // potentially by an overidden setting on a per-method basis. String highBitCharacters = "X\u00a3\u00c7\u00eb\u00ae"; printHeader("Encoding Demo"); System.out.print("Default JVM encoding: "); System.out.println(System.getProperty("file.encoding")); System.out.print("Test high bit character output: "); System.out.println(highBitCharacters); System.out.print("It takes "); System.out.print(highBitCharacters.getBytes().length); System.out.println(" bytes to store this string."); try { System.out.print("Windows Cp1252 Characters: "); String winstring = new String( highBitCharacters.getBytes(), WindowsLatin1); (continues) Iverson_ch12.qxd 1/17/05 2:42 PM Page 169 Character Encodings 169 Listing 12-2 (continued ) System.out.println(winstring); System.out.println(); System.out.println("Everything looks fine, but some"); System.out.println("systems automatically convert the"); System.out.println("data. Here, note the lossy "); System.out.println("conversion to ? characters:"); System.out.println(); System.out.print("ASCII Characters: "); String asciiString = new String(highBitCharacters.getBytes(), "ASCII"); System.out.println(asciiString); System.out.println(); System.out.println( "Commons Encoding supports converting"); System.out.println("bytes to two-digit 0-f hex codes."); System.out.println(); System.out.print("Hex Characters: "); byte[] hexresults; hexresults = new Hex().encode(highBitCharacters.getBytes()); System.out.println(new String(hexresults)); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } } As we can see in the output shown in Listing 12-3, converting the string from Unicode code points to Cp1252 (the default encoding on a US English Windows system) works fine, but the encoding conversion to pure ASCII results in the loss of information. Listing 12-3 Encoding Example Results ================================ Encoding Demo ================================ Default JVM encoding: Cp1252 Test high bit character output: X£Çë® It takes 5 bytes to store this string. Windows Cp1252 Characters: X£Çë® Everything looks fine, but some systems automatically convert the data. Here, note the lossy conversion to ? characters: ASCII Characters: X???? Commons Encoding supports converting bytes to two-digit 0-f hex codes. Hex Characters: 58a3c7ebae Iverson_ch12.qxd 1/17/05 2:42 PM Page 170 170 Codec Chapter 12 This example shows us the first use of the Apache Commons project—the abil- ity to translate a series of characters from raw byte data to a hex representa- tion. In a hex representation, each byte is transformed to a two-letter ASCII representation, 0-f. The hex format, while potentially useful for reading and writing binary data to an ASCII representation, is not as well known or popu- lar as the Base64 format. BASE64 ENCODING Having seen how character encodings can have a major impact on our data, let’s look at how the Base64 Codec can be used to convert binary data to a for- mat easily represented by ASCII characters. Many systems understand and can easily transmit binary data when encoding using Base64—in particular, Base64 encoding is commonly found when sending binary files as email attachments. Listing 12-4 shows how a binary file (in this case, a small GIF) can be loaded and converted to 7-bit ASCII characters. Generally speaking, 7-bit ASCII characters are safe for transmission across a variety of systems—even copying and pasting from one application to another on a wide variety of systems. Listing 12-4 Base64 File Encoding Source public static void fileEncodingDemo() { printHeader("Base64 File Encoding Test"); java.io.File myFile = new java.io.File("demo.gif"); try { if (myFile.exists()); { FileInputStream myFileContents = new FileInputStream(myFile); byte[] fileContents = new byte[(int)myFile.length()]; myFileContents.read(fileContents); String myGIF = new String(fileContents); System.out.println( "Notice the strange, non-ASCII characters..."); System.out.println(myGIF.substring(0, 79)); System.out.println(); byte[] result; result = Base64.encodeBase64Chunked(fileContents); System.out.println( "Note all ASCII characters, and that the data "); (continues) Iverson_ch12.qxd 1/17/05 2:42 PM Page 171 URL Form Encoding 171 Listing 12-4 (continued ) System.out.println( "is automatically formatted to 79 characters"); System.out.println(new String(result)); } } catch (Exception e) { e.printStackTrace(); } } When run, the application produces output as shown in Listing 12-5 (for a very small test GIF). You’ll notice that instead of using the simple encode() method, we took advantage of a encodeBase64Chunked() utility method to retrieve data already broken into 76 character wide columns—easily used on even legacy 80 character column terminal displays. Listing 12-5 Base64 File Encoding Results ================================ Base64 File Encoding Test ================================ Notice the strange, non-ASCII characters... GIF89a<> Note all ASCII characters, and that the data is automatically formatted to 76 characters R0lGODlhIAAgAIAAAP///wAAACwAAAAAIAAgAAACUkyAqcuNdpycAEaKk72Zbt45HxguI1k+Z8qc Bqu4L1zJaGbPaa6HfI/73UTCYatojCGTqiVmCfFAgaYpVWO91rIobrTqBYW/zTF2PENbtuq2pQAA Ow== URL FORM ENCODING Uniform Resource Locators (URLs) are wonderful things—they allow us to point to information all over the Internet and local networks. We are all famil- iar with such strings as http://www.example.com/page.jsp?id=1. If you have done much in the way of web application development, you recognize that this string points to a specific JSP called page.jsp on a web server with a domain name of www.example.com and is sending a parameter called id with a value of 1. Special characters, such as ? and =, are used as tokens by the server to indi- cate how to parse the incoming request. Now, let’s imagine that we want to use a parameter value that happens to have a ?, =, or even a space character. This is allowable according to the specification using a special encoding format (www-form-urlencoded, com- monly referred to as URL encoding). Make sure, however, that you are encod- ing the data to be sent along as a parameter, not the URL itself. Listing 12-6 shows an example of how a complex URL parameter is encoded and then appended to the URL. Iverson_ch12.qxd 1/17/05 2:42 PM Page 172 172 Codec Chapter 12 Listing 12-6 URL Parameter Encoding Source public static void formURLEncodingDemo() { printHeader("Form URL Encoding Demo"); try { String badParameterValue = "http://www.example.org/page.jsp?foo=bar next"; System.out.println( "Here is an example of a difficult "); System.out.println("string to use as a URL parameter:"); System.out.println(badParameterValue); byte[] badURLresult = new URLCodec().encode(badParameterValue.getBytes()); System.out.println(); System.out.println("Here is the string, properly"); System.out.println("formatted for use as a link:"); System.out.println( "http://www.example.com/view.jsp?url=" + new String(badURLresult)); System.out.println(); } catch (Exception e) { e.printStackTrace(); } } As shown in Listing 12-7, the parameter passed along is another URL. This could be useful in a variety of situations—for example, our web application might verify the availability of a web site, and so a URL needs to be passed along as a parameter. Listing 12-7 URL Parameter Encoding Results ================================ Form URL Encoding Demo ================================ Here is an example of a difficult string to use as a URL parameter: http://www.example.org/page.jsp?foo=bar next Here is the string, properly formatted for use as a link: http://www.example.com/view.jsp?url=http%3A%2F%2Fwww.example. org%2Fpage.jsp%3Ffoo%3Dbar+next Iverson_ch12.qxd 1/17/05 2:42 PM Page 173 Hash Generation 173 HASH GENERATION Not all encoding systems are bidirectional. Some, such as JPEG, are inherently lossy—the conversion process discards some data in the name of compression. MD5 and SHA, on the other hand, allow you to encode a particular stream of bytes to generate a hash—a fingerprint of that stream of bytes. This hash is specifically intended to not allow you to decode back to the original data. What Are SHA and MD5? "SHA-1: The Secure Hash Algorithm (SHA) was developed by NIST and is specified in the Secure Hash Standard (SHS, FIPS 180). SHA-1 is a revi- sion to this version and was published in 1994. It is also described in the ANSI X9.30 (part 2) standard. SHA-1 produces a 160-bit (20 byte) mes- sage digest. Although slower than MD5, this larger digest size makes it stronger against brute force attacks. MD5: MD5 was developed by Professor Ronald L. Rivest in 1994. Its 128 bit (16 byte) message digest makes it a faster implementation than SHA-1. In both cases, the fingerprint (message digest) is also non-reversible. . . . your data cannot be retrieved from the message digest, yet as stated ear- lier, the digest uniquely identifies the data." From http://www.secure-hash-algorithm-md5-sha-1.co.uk/ The precise use of this functionality is up to your application. For exam- ple, for security reasons, you may not want to store user passwords in your database as clear text but rather as an MD5 hash of the password. You may want to perform an MD5 hash of a file before sending it to someone and then send the hash in another email so the recipient can verify that the file sent is the same as the file received (you will often see reference to this on the Apache Software Foundation download pages). Many applications use an MD5 hash routine to generate serial numbers for registered users. Regardless of your particular application, Apache Codec provides a sim- ple, easy-to-use mechanism for generating MD5 and SHA hash values. Listing 12-8 shows how both a password and a bit of text can be converted to their hash values. Listing 12-8 MD5 and SHA Digest Generation Source public static void hashEncodingDemo() { String shakespeareText = "ROMEO : \n" + "Peace, peace, Mercutio, peace!\n" + "Thou talk'st of nothing.\n" + "\n" (continues) Iverson_ch12.qxd 1/17/05 2:42 PM Page 174 174 Codec Chapter 12 Listing 12-8 (continued ) + "MERCUTIO : \n" + "True, I talk of dreams,\n" + "Which are the children of an idle brain,\n" + "Begot of nothing but vain fantasy,\n" + "Which is as thin of substance as the air\n" + "And more inconstant than the wind, who wooes\n" + "Even now the frozen bosom of the north,\n" + "And, being anger'd, puffs away from thence,\n" + "Turning his face to the dew-dropping south."; printHeader("Hash Encoding Demo"); String password_text = "my_password"; System.out.println("MD5 Password Encryption:"); String encryption_result = DigestUtils.md5Hex(password_text); System.out.println(encryption_result); System.out.println(encryption_result.length()); System.out.println(); System.out.println("MD5 Document Fingerprint:"); encryption_result = DigestUtils.md5Hex(shakespeareText); System.out.println(encryption_result); System.out.println(encryption_result.length()); System.out.println(); System.out.println("SHA Password Encyption:"); encryption_result = DigestUtils.shaHex(password_text); System.out.println(encryption_result); System.out.println(encryption_result.length()); System.out.println(); System.out.println("SHA Document Fingerprint:"); encryption_result = DigestUtils.shaHex(shakespeareText); System.out.println(encryption_result); System.out.println(encryption_result.length()); } As can be seen from the results of the example, shown in Listing 12-9, MD5 generates 32-character-long hash codes. The hash is the same length for both a password less than 32 characters and a snippet of text much longer than 32 characters. SHA performs a similar function, taking a bit more time to gener- ate a more sophisticated (and secure) 40-character hash. Listing 12-9 MD5 and SHA Digest Generation Results ================================ Hash Encoding Demo ================================ MD5 Password Encryption: a865a7e0ddbf35fa6f6a232e0893bea4 32 MD5 Document Fingerprint: bf5dea92a8a43beee75a7d3f44b41cf4 32 (continues) Iverson_ch12.qxd 1/17/05 2:42 PM Page 175 Phonetic Analysis 175 Listing 12-9 (continued ) SHA Password Encyption: 5eb942810a75ebc850972a89285d570d484c89c4 40 SHA Document Fingerprint: 7b810d5b8e4853c91071895117543cd1927a4604 40 PHONETIC ANALYSIS In this chapter we’ve looked at traditional encoding methods and also hash generation, but Codec offers an additional set of classes for use in phonetic analysis. It’s beyond the scope of this text to delve into the theory behind Soundex and Metaphone phonetic analysis, but suffice to say that these algorithms pro- vide different mechanisms for generating a phonetic key. This key is designed to be able to help answer the question, "How much does this word sound like another?" Table 12-1 shows how different phonetic algorithms included with Codec translate words into phonetic keys. Depending on the application you are try- ing to build, different algorithms may be of interest. For example, a spell- checking application might use Metaphone to determine alternative words as part of a spell-checking routine, whereas a voice-recognition system might rely on the RefinedSoundEx algorithm to determine the most likely words the speaker is trying to convey. Notice that while SoundEx produces the same length key for all words, the other algorithms produce variable length keys. Table 12-1 Phonetic Algorithm Results Word hello fellow mellow monster monstrous SoundEx H400 F400 M400 M523 M523 RefinedSoundEx H070 F2070 M8070 M8083609 M80836903 Metaphone HL FL ML MNST MNST Double Metaphone HL FL ML MNST MNST By using these algorithms and a very large set of words, you can gener- ate a set of keys linking the words phonetically—the fundamentals needed for a spell checker. Listing 12-10 shows the code used to generate the terms as shown in Table 12-1. Iverson_ch12.qxd 1/17/05 2:42 PM Page 176 176 Codec Chapter 12 Listing 12-10 Phonetic Key Generation Source public static void phoneticDemo() { printHeader("Phonetic Demo"); String[] words = { "hello", "fellow", "mellow", "monster", "monstrous" }; System.out.println("Notice the sounds of the words, and"); System.out.println("how the sounds are translated into 4"); System.out.println("character character flags."); System.out.print("Word, SoundEx, RefinedSoundEx, "); System.out.println("Metaphone DoubleMetaphone"); for (int i = 0; i < words.length; i++) { System.out.print(words[i] + ", "); System.out.print(new Soundex().encode(words[i]) + ", "); System.out.print( new RefinedSoundex().encode(words[i]) + ", "); System.out.print( new Metaphone().encode(words[i]) + ", "); System.out.print( new DoubleMetaphone().encode(words[i])); System.out.println(); } } For more information on phonetic analysis, see the following sites: ☞ http://encyclopedia.thefreedictionary.com/Soundex ☞ http://www.archives.gov/research_room/genealogy/census/soundex.html ☞ http://aspell.sourceforge.net/metaphone/ SUMMARY The Codec package contains utilities that are useful in unusual places. For example, you might use the phonetic routines to help provide corrected spellings for free text searches. You also might use the encoding of binary data to a string to help send data over the network. By adding these to your tool- box, you can provide richer services while focusing on unique aspects of your application. Iverson_ch12.qxd 1/17/05 2:42 PM Page 177 Summary 177 Project Ideas Write an application that parses arbitrarily large bodies of text and gen- erates a database of phonetic data. What are the best ways to store this? How large is the generated database? Write an application that calculates the MD5 and SHA results for large bodies of text and binary data. What are the performance tradeoffs? How large does a data set have to be before this becomes an issue? Write a command-line application to convert files to Base64 and back again. How does this compare to converting files to .zip and back? When would you use Base64, and when would you use .zip? Iverson_ch12.qxd 1/17/05 2:42 PM Page 178 Iverson_ch13.qxd 1/17/05 2:36 PM Page 179 C H A P T E R 13 CLI (Command-Line Interface) The Apache Jakarta Commons CLI package is intended to assist in the cre- ation of command-line applications. In conjunction with the String manipula- tion afforded by the Commons Lang package, aspiring developers could potentially create quite sophisticated console applications. This package takes care of the complexities of parsing incoming arguments, validating the argu- ments, and displaying help information. In this chapter, a simple utility function (searching various paths for the location(s) of a particular class file) is first presented from a high level, then a command-line wrapper based on this utility using CLI is shown, and for com- pleteness, the full implementation of the class search tool is presented. CLASSPATHTOOL OVERVIEW The ClassPathTool utility is intended to allow a user to search class path(s) for a particular Java class file, specified by name. The ClassPathTool is smart enough to handle two special cases—first, searching for a particular path and file, and second, looking for a matching entry in a JAR or ZIP file. This serves two purposes: first, a user can search an arbitrary directory for a desired class file hidden in an unknown JAR file (for example, if a particular class is refer- enced by a source file). Second, a user may want to search the current class path to determine if the expected version of the class is actually on the class path. This is increasingly common given the complexity of server-side Java development and the proliferation of popular utility libraries (such as Jakarta Commons). The ClassPathTool utility, as shown in Figure 13-1, does not actually have a user interface. It is exposed as a simple JavaBean-style library, with proper- ties available to set options and a single getEntries() method to perform the search as configured. There is no reason that the ClassPathTool utility could not have a Swing or even web user interface, but those interfaces may be pro- hibitive in certain server environments. Therefore, the CommandLineDemo class is provided as a wrapper, making use of Commons CLI. 179 Iverson_ch13.qxd 1/17/05 2:36 PM Page 180 . w e i v r e v o e l p m a x e I L C 1 - 3 1 e r u g F i 180 Iverson_ch13.qxd 1/17/05 2:36 PM Page 181 Building a Command-Line Interface 181 BUILDING A COMMAND-LINE INTERFACE As shown in the preparation code of CommandLineDemo in Listing 13-1, the short versions of the arguments for the command-line application are provided as String values. These values are used in several places in the application. As part of the initialization, the getOptions() method returns a con- figured set of CLI options. These options are used both to parse the incom- ing arguments as well as generate the output of the "help" documentation displayed upon request or when a user enters incorrect input. Various Option objects are used to configure the various kinds of options—for example, some options are merely off/on switches, whereas others accept an additional argument. Listing 13-1 CLI Example Initialization package com.cascadetg.ch13; import java.util.Iterator; import java.util.Map; import org.apache.commons.cli.CommandLine; import org.apache.commons.cli.HelpFormatter; import org.apache.commons.cli.MissingArgumentException; import org.apache.commons.cli.Option; import org.apache.commons.cli.Options; import org.apache.commons.cli.PosixParser; import org.apache.commons.cli.CommandLineParser; import org.apache.commons.lang.SystemUtils; public class CommandLineDemo { public static final String VERBOSE = "v"; public static final String RECURSION = "r"; public static final String IGNORE_JAVA_CP = "ijcp"; public static final String IGNORE_BOOT_CP = "ibcp"; public static final String USER_CP = "p"; public static final String SEARCH = "s"; public static final String HELP = "?"; public static final boolean HAS_ARGUMENTS = true; public static final boolean NO_ARGUMENTS = false; public static Options getOptions() { Options myOptions = new Options(); Option verbose = new Option(VERBOSE, "verbose", NO_ARGUMENTS, "Show additional details"); Option help = new Option(HELP, "help", NO_ARGUMENTS, "Show available options"); (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 182 182 CLI (Command-Line Interface) Chapter 13 Listing 13-1 (continued ) Option recursive = new Option( RECURSION, "recursion", HAS_ARGUMENTS, "Search recursively in specified directories. Default (-1) is" + " unlimited depth. 0 for no recursion."); recursive.setType(Integer.class); recursive.setArgName("depth"); Option ignoreJavaClassPath = new Option(IGNORE_JAVA_CP, "ignoreJavaCP", NO_ARGUMENTS, "Ignore the system Java class path setting"); Option ignoreBootClassPath = new Option(IGNORE_BOOT_CP, "ignoreBootCP", NO_ARGUMENTS, "Ignore the Java boot class path setting"); Option searchClass = new Option(SEARCH, "search", HAS_ARGUMENTS, "REQUIRED: The fully qualified class name to find " + "(e.g. java.lang.String)"); searchClass.setArgName("classname"); searchClass.setType(String.class); Option searchDirectory = new Option(USER_CP, "path", HAS_ARGUMENTS, "Set additional user defined search path[s]"); searchDirectory.setArgName("path[" + SystemUtils.PATH_SEPARATOR + "path...]"); searchDirectory.setType(String.class); myOptions.addOption(searchClass); myOptions.addOption(verbose); myOptions.addOption(recursive); myOptions.addOption(ignoreJavaClassPath); myOptions.addOption(ignoreBootClassPath); myOptions.addOption(searchDirectory); myOptions.addOption(help); return myOptions; } Listing 13-2 shows how the output is generated upon successful configuration and execution of ClassPathTool. The returned information is a Map, with the key being the path of the located directory or file and the value being the time- stamp of the file. Listing 13-2 CLI Output public static void displayResults(ClassPathTool cp) { Map foundEntries = cp.getEntries(); if (foundEntries.size() > 0) { System.out.println(); System.out.println("Found " + cp.getSearchClass() + " at :"); (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 183 Building a Command-Line Interface 183 Listing 13-2 (continued ) Iterator found = foundEntries.keySet().iterator(); while (found.hasNext()) { Object foundFile = found.next(); System.out.print("["); System.out.print(foundEntries.get(foundFile)); System.out.print("] "); System.out.println(foundFile.toString()); } System.out.println(); System.out.println("Files checked: " + cp.filesChecked); System.out.println("Directories checked: " + cp.directoriesChecked); System.out.println("Elapsed time: " + cp.getTimeElapsed() / 1000 + "." + cp.getTimeElapsed() % 1000 + " sec"); } else { System.out.println("Unable to find entry."); } } Listing 13-3 shows how the command-line options parsed by CLI (via the CommandLine object) are used to configure the ClassPathTool instance. Given that the CommandLine object performs the "heavy lifting" of parsing the input, the actual configuration and execution of ClassPathTool is quite straightforward. Listing 13-3 Using CLI to Configure ClassPathTool public static void useApp(CommandLine line) throws Exception { if (!line.hasOption(SEARCH)) { throw new MissingArgumentException( "No search class specified."); } else { System.out.println("Searching for " + line.getOptionValue(SEARCH) + "..."); } ClassPathTool cp = new ClassPathTool(); cp.setSearchClass(line.getOptionValue(SEARCH)); if (line.hasOption(RECURSION)) { cp.setMaxSearchDepth(Integer.parseInt(line .getOptionValue(RECURSION))); } (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 184 184 CLI (Command-Line Interface) Chapter 13 Listing 13-3 (continued ) if (line.hasOption(VERBOSE)) cp.setVerbose(true); if (line.hasOption(IGNORE_JAVA_CP)) cp.setUseJavaClassPath(false); if (line.hasOption(IGNORE_BOOT_CP)) cp.setUseBootClassPath(false); if (line.hasOption(USER_CP)) cp.setUserDefinedClassPath(line .getOptionValue(USER_CP)); displayResults(cp); } Listing 13-4 shows the actual main() method and the core process behind the use of CLI. A CommandLineParser is created, the options defined in getOptions and the command-line arguments are passed to the parser, and assuming no exceptions are thrown, execution proceeds normally. If the user entered -? as an option or an exception is thrown, the application prints the help output and terminates. Note that the same options used to configure the parser are used to generate the help information. Listing 13-4 Running ClassPathTool with CLI public static void main(String[] args) { try { CommandLineParser parser = new PosixParser(); CommandLine line = parser.parse(getOptions(), args); if (line.hasOption("?")) { HelpFormatter formatter = new HelpFormatter(); formatter.printHelp("CommandLineDemo", getOptions()); } else { useApp(line); } } catch (Exception e) { System.out.println("ERROR: " + e.getClass()); System.out.println(e.getMessage()); HelpFormatter formatter = new HelpFormatter(); formatter.printHelp("CommandLineDemo", getOptions()); } } } RUNNING COMMAND LINE As shown in Figure 13-2, running the command line with no arguments results in the display of the help text, generated by the options passed to CLI. Iverson_ch13.qxd 1/17/05 2:36 PM Page 185 Running Command Line 185 Figure 13-2 Running without arguments. Passing in a single -s java.lang.String argument, as shown in Figure 13-3, searches the default system class path. As can be seen, the class can be found in the rt.jar file supplied with the JRE. Figure 13-3 A simple search. As shown in Figure 13-4, a more complex search can be performed by passing -s org.apache.commons.lang.StringUtils -p C:\devenv\ -r 6 as an argu- ment. This searches for all instances of org.apache.commons.lang.StringUtils in the C:\devenv\ directory, with a maximum recursion depth of 6. As can be seen, a number of instances of the Lang library were found on my system. Some of these explicitly contain a reference to the version of the library; several do not. It’s easy to imagine running this utility to search the installation of an applica- tion server to troubleshoot class path problems. Iverson_ch13.qxd 1/18/05 11:50 AM Page 186 186 CLI (Command-Line Interface) Chapter 13 Figure 13-4 A complex search. BEHIND THE SCENES WITH CLASSPATHTOOL Finally, for the sake of completeness, Listing 13-5 shows the source for the class path search routines used by ClassPathTool. It is highly recursive, and on systems with symbolic links (such as most UNIX systems), you may want to either change the default maximum search depth or be sure to set the recur- sion (-r) to a non-negative number. Listing 13-5 Searching for Classes package com.cascadetg.ch13; import java.io.File; import java.util.*; import java.util.zip.*; (continues) Iverson_ch13.qxd 1/18/05 11:50 AM Page 187 Behind the Scenes with ClassPathTool 187 Listing 13-5 (continued ) import org.apache.commons.lang.SystemUtils; public class ClassPathTool { // Utility values, initialized once static Properties systemProps = System.getProperties(); // Class configuration boolean verbose = false; boolean useJavaClassPath = true; boolean useBootClassPath = true; String userDefinedClassPath; String searchClass = "java.lang.String"; // Reporting statistics int filesChecked = 0; int directoriesChecked = 0; long timeElapsed = 0; // The maximum recursion depth to check, or -1 for infinite int maxSearchDepth = -1; // Used during search, the directory version (e.g. // \java\lang\String.class private String directorySearch; // Used during search, the ZIP entry version (e.g. // /java/lang/String.class private String zipEntrySearch; public List getPaths() { String[] paths = new String[3]; if (useJavaClassPath) paths[0] = System.getProperty("java.class.path"); if (useBootClassPath) paths[1] = System .getProperty("sun.boot.class.path"); paths[2] = userDefinedClassPath; java.util.List results = new LinkedList(); for (int i = 0; i < 3; i++) { if (paths[i] != null) { new StringTokenizer( StringTokenizer myJavaClassPathTokenizer = paths[i], SystemUtils.PATH_SEPARATOR, false); while (myJavaClassPathTokenizer .hasMoreElements()) results.add(myJavaClassPathTokenizer .nextElement()); } } return results; } (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 188 188 CLI (Command-Line Interface) Chapter 13 Listing 13-5 (continued ) public void findItem(Map foundEntries, String directory, int depth) { boolean pathIsZip = false; if (directory.endsWith(".jar")) pathIsZip = true; if (directory.endsWith(".zip")) pathIsZip = true; File myFile = new File(directory); if (myFile.isDirectory()) { directoriesChecked++; File checkLoc = new File(myFile.getPath() + SystemUtils.FILE_SEPARATOR + directorySearch); if (checkLoc.exists()) { foundEntries.put(checkLoc.getAbsolutePath(), new java.util.Date(checkLoc .lastModified()) .toLocaleString()); } if (maxSearchDepth != 0) { File[] items = myFile.listFiles(); for (int i = 0; i < items.length; i++) { boolean keepRecursing = true; if (maxSearchDepth != -1) if (depth > maxSearchDepth) keepRecursing = false; if (keepRecursing) { findItem(foundEntries, items[i] .getAbsolutePath(), (depth + 1)); } } } } if (pathIsZip) { ZipFile myZip = null; try { if (myFile.exists()) { filesChecked++; myZip = new ZipFile(myFile, ZipFile.OPEN_READ); ZipEntry myEntry = myZip .getEntry(zipEntrySearch); if (myEntry != null) { foundEntries.put(myZip.getName(), (continues) Iverson_ch13.qxd 1/18/05 11:50 AM Page 189 Behind the Scenes with ClassPathTool 189 Listing 13-5 (continued ) new java.util.Date(myFile .lastModified()) .toLocaleString()); } } } catch (Exception e) { System.err.print("While opening file: " + directory + " "); if (verbose) { e.printStackTrace(); } else { System.err.println(e.getMessage()); } } finally { try { if (myZip != null) myZip.close(); } catch (Exception e) { // Silent failure. } } } } /** Performs the search based on the current settings. */ public java.util.Map getEntries() { long startTime = System.currentTimeMillis(); HashMap foundEntries = new HashMap(); Iterator paths = getPaths().iterator(); directorySearch = searchClass.replace('.', SystemUtils.FILE_SEPARATOR.charAt(0)); directorySearch = directorySearch + ".class"; zipEntrySearch = searchClass.replace('.', '/'); zipEntrySearch = zipEntrySearch + ".class"; while (paths.hasNext()) { String current = (String) paths.next(); if (verbose) System.out findItem(foundEntries, current, 0); .println("Base search: " + current); } timeElapsed = System.currentTimeMillis() - startTime; return foundEntries; } (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 190 190 CLI (Command-Line Interface) Chapter 13 Listing 13-5 (continued ) public void listProp() { Iterator myPropKeys = systemProps.keySet().iterator(); while (myPropKeys.hasNext()) { String key = myPropKeys.next().toString(); System.out.print(key); System.out.print(":"); System.out.println(systemProps.getProperty(key)); } } public static void main(String[] argv) { ClassPathTool cp = new ClassPathTool(); String input = "org.hsqldb.Database"; cp.setUserDefinedClassPath("C:\\devenv\\"); cp.setVerbose(false); cp.setMaxSearchDepth(4); Map foundEntries = cp.getEntries(); System.out.println("Files checked: " + cp.filesChecked); System.out.println("Directories checked: " + cp.directoriesChecked); System.out.println("Elapsed time: " + cp.getTimeElapsed() / 1000 + "." + cp.getTimeElapsed() % 1000 + " sec"); if (foundEntries.size() > 0) { System.out.println("Found in:"); Iterator found = foundEntries.keySet().iterator(); while (found.hasNext()) { Object foundFile = found.next(); System.out.print(foundFile.toString()); System.out.print(" ["); System.out.print(foundEntries.get(foundFile)); System.out.println("]"); } } else { System.out.println("Unable to find entry."); } } public boolean isVerbose() { return verbose; } public void setVerbose(boolean verbose) { this.verbose = verbose; } public String getUserDefinedClassPath() { return userDefinedClassPath; } public void setUserDefinedClassPath(String userDefinedClassPath) { this.userDefinedClassPath = userDefinedClassPath; } public String getSearchClass() { return searchClass; } public void setSearchClass(String searchClass) { this.searchClass = searchClass; } public boolean isUseBootClassPath() { return useBootClassPath; } (continues) Iverson_ch13.qxd 1/17/05 2:36 PM Page 191 Summary 191 Listing 13-5 (continued ) public void setUseBootClassPath(boolean useBootClassPath) { this.useBootClassPath = useBootClassPath; } public boolean isUseJavaClassPath() { return useJavaClassPath; } public void setUseJavaClassPath(boolean useJavaClassPath) { this.useJavaClassPath = useJavaClassPath; } public int getDirectoriesChecked() { return directoriesChecked; } public int getFilesChecked() { return filesChecked; } public int getMaxSearchDepth() { return maxSearchDepth; } public void setMaxSearchDepth(int maxSearchDepth) { this.maxSearchDepth = maxSearchDepth; } public long getTimeElapsed() { return timeElapsed; } } SUMMARY While many applications provide a graphical user interface via Swing or HTML, it’s not always the appropriate interface. System administrators in particular often appreciate a command-line interface, as it is easier to work into a scripting environment or via a remote login (such as SSH). By building an application using the CLI package, system administrators will find your software to be easier to use. Project Ideas How hard is it to convert an existing Swing application to support a command-line interface? Instead of accepting arguments via main(), try adding a command-line text box to a Swing application. Is this interactive application easier to use? How about speed of command entry? Iverson_ch13.qxd 1/17/05 2:36 PM Page 192 Iverson_ch14.qxd 1/17/05 2:42 PM Page 193 C H A P T E R 14 Other Projects In addition to the projects described in this book, a variety of Commons proj- ects, both proper and sandbox, are available for further exploration. ADDITIONAL COMMONS PROPER PROJECTS The Commons proper projects not described in detail in this book are described in a bit more detail in the following. For more information on these packages, visit the http://jakarta.apache.org/commons/ web site. Betwixt Services for mapping JavaBeans to XML documents, and vice versa. Intended for use when a JavaBean wants to be serialized to XML. Note that JDK 1.4 introduced long-term serialization-to-XML capability (http://java.sun.com/ j2se/1.4.2/docs/guide/beans/changes14.html). Chain Provides a "Chain of Responsibility" pattern implementation for organizing complex processing flows. As of this writing, despite the status as a proper package (not sandbox), there have been no official releases. Configuration Tools to assist in the reading of configuration/preferences files in various for- mats. Allows for configuration information from Properties files, XML docu- ments, JNDI, and JDBC data sources to be accessed in a unified manner. Daemon An alternative invocation mechanism for UNIX-daemon-like Java code. Speci- fically, this project contains native code for receiving system status notifications 193 Iverson_ch14.qxd 1/17/05 2:42 PM Page 194 194 Other Projects Chapter 14 from the operating system for both UNIX and Windows. If you are writing server code and are interested in this project, you may also be interested in the JDesktop Integration Components (JDIC), https://jdic.dev.java.net/. DbUtils JDBC helper library that factors out mundane resource cleanup code for com- mon database tasks. DbUtils is intended to remove the drudgery of raw JDBC, but it is not an object/relational database package. It is simply a helper library. Digester An XML-to-Java-object mapping utility commonly used for parsing XML configuration files. Intended to serve as a common framework for dealing with large configuration files; for many application developers, starting with a generic XML library (such as JDOM, http://www.jdom.org/) may be more appropriate. Discovery Provides tools for locating resources (including classes) by mapping service/reference names to resource names using a variety of schemes. It is only at a 0.2 release. EL An interpreter for the Expression Language defined by the JavaServer Pages™ specification, version 2.0. This might be useful as a scripting language to be embedded in certain applications. IO Collection of I/O utilities, including stream implementations, file filters, and endian classes. The org.apache.commons.io.CopyUtils class contains a compre- hensive set of static methods for copying from a String, byte[], InputStream, or Reader to an OutputStream or Writer. Similarly, the org.apache.commons. io.IOUtils class contains additional tools for safely closing streams and cre- ating String and byte arrays from streams and readers. The org.apache. commons.io.FileUtils class contains methods for retrieving different compo- nents of a file path (directory name, file base name, file extension), methods for copying files to other files and directories, and methods for querying, delet- ing, and cleaning directories. Additional classes provide filters for use with FileDialog, or for converting the endian ordering of bytes. Iverson_ch14.qxd 1/17/05 2:42 PM Page 195 Additional Commons Proper Projects 195 Jelly XML-based scripting and processing engine. While Jelly has found some suc- cess in projects such as Maven, the general consensus is that XML is a poor choice for a programming language—even the creator of Jelly apologized at http://radio.weblogs.com/0112098/2004/03/26.html#a472. Jexl An expression language that extends the Expression Language of the JSTL. Note that this package is not compatible with JSTL or JSP—it is a nonstan- dard expression language. Latka An HTTP functional testing suite for automated QA, acceptance, and regres- sion testing. XML is used to define HTTP(S) requests and validation tests. Launcher Cross-platform Java application launcher. Eliminates the need for a batch or shell script to launch a Java class. Originally developed for Tomcat, it allows for complex configurations of class path and system properties. Math Library of lightweight, self-contained mathematics and statistics components addressing the common practical problems not immediately available in the Java programming language. This includes basic statistics and linear equa- tion support. Modeler Provides mechanisms to create Model MBeans compatible with the Java Management Extensions (JMX) specification. If you wish to expose manage- ment of your application via JMX, you will likely want to investigate this package. Primitives Smaller, faster, and easier to work with types supporting Java primitive types, with an emphasis on collections. The provided collection of types and utilities is optimized for working with Java primitives (boolean, byte, char, double, float, int, long, short). Iverson_ch14.qxd 1/17/05 2:42 PM Page 196 196 Other Projects Chapter 14 Validator Simple, extendable framework to define validation methods and validation rules in an XML file. Supports internationalization of rules and error mes- sages. Includes basic validation rules for credit card numbers, dates, email addresses, and URLs. SANDBOX PROJECTS The sandbox projects, generally speaking, are not as stable or popular as the proper projects. You should expect both functionality and interfaces to change. Virtually all of the sandbox projects have not released official binary or source releases—expect to use CVS to access the latest source. Attributes Attributes provides a runtime API to metadata attributes such as doclet tags, inspired by the Nanning and XRAI projects, as well as JSR 175 and C# attrib- utes. Values may be specified in code using a @@ symbol, similar to Java 5.0 (aka JDK 1.5) annotations as specified by JSR 175 (http://www.jcp.org/en/ jsr/detail?id=175) or XDoclet (http://xdoclet.sourceforge.net/). The Attri- butes package will parse your source files and generate Java source files corre- sponding to the attributes. Cache Cache provides object-caching services. As of this writing, this project has not released any official binary builds. Clazz Clazz focuses on introspection and class manipulation. As of this writing, this project has not released any official binary builds. Compress Commons Compress defines an API for working with tar, zip, and bzip2 files. The JDK offers built-in support for ZIP files, and while this project has not released any official binary builds as of this writing, you may want to investi- gate the CVS repository if you need access to tar or bzip2 files. Convert Convert aims to provide a single library dedicated to the task of converting an object of one type to another. No official binary builds have been released. Iverson_ch14.qxd 1/17/05 2:42 PM Page 197 Sandbox Projects Email 197 Email provides a simple library for sending email from Java. It aims to sim- plify certain tasks on top of the JavaMail API (http://java.sun.com/products/ javamail/), in particular multipart email and HTML email with embedded images. No official binary builds have been released. Events Events provides additional classes for firing and handling events. It focuses on the Java Collections Framework, providing decorators to other collections that fire events. No official binary builds have been released. FeedParser Generic FeedParser interface and concrete implementations for Atom, FOAF, OPML and RSS. No official binary builds have been released. Functor A functor is a function that can be manipulated as an object, or an object rep- resenting a single, generic function. While this package has not released any official binary releases, additional information on functors is available as part of the Collections package. Id Id is a component used to generate unique identifiers, including numeric, long, session, alphanumeric, and UUID identifiers. No official binary releases. JJar Jakarta JAR Archive Repository. An attempt to build a single online repository to access binaries for various projects. For example, you might want to distrib- ute an Ant task that will automatically download a required library if it’s not present. Therefore, this project does not represent a particular lump of code so much as a common point for downloading other Jakarta projects. This project is largely considered superseded by the Apache Depot project (http://incubator.apache.org/depot/). Mapper Mapper is a thin abstraction layer around a project’s chosen data mapping technology (a.k.a. DAO pattern). It purports to isolate an application from the underlying persistence store—it is unclear how effective this is in practice. Iverson_ch14.qxd 1/17/05 2:42 PM Page 198 198 Other Projects Chapter 14 Messenger Messenger is an easy to use and lightweight framework for working with JMS in the web tier. Intended to put a friendly face on JMS, it also can serve as a bridge between two different JMS engines. Resources Resources provides a lightweight framework for defining and looking up inter- nationalized message strings keyed by a java.util.Locale and a message key. Scaffold Scaffold is a toolkit for building web applications. As of this writing, it consists of a variety of loosely coupled utility methods. SQL Commons SQL is a component for working with databases and generating DDL. It contains a simple set of beans that represent a relational database schema such as a Database, Table, Column, etc. It even allows for simple map- pings of a table to objects. Most projects will likely want to adopt a more robust object/relational package. ThreadPool ThreadPool is a simple component for asynchronously dispatching work to another thread in a pool for simple multithreaded programming. This project has largely been superseded by the util.concurrency package available at http://gee.cs.oswego.edu/dl and included in Java 2 5.0 (a.k.a. JDK 1.5). Transaction Transaction provides a set of utility classes for transactional data structures, locks, and a transactional file system. Of particular interest is support for dec- orating a Map to render it capable of transactional behavior (with an optional interface to plug in to a JCA implementation and participate in distributed JTA transactions). A locking package and transactional file system wrapper are also provided. VFS VFS is a Virtual File System component for treating various file systems as a single logical file system. File systems supported include CIFS, FTP, local files, HTTP/HTTPS, SFTP, temporary files, WebDAV, ZIP, and JAR. Iverson_ch14.qxd 1/17/05 2:42 PM Page 199 Summary Workflow 199 Workflow provides a framework for building workflow management systems in XML. No official binary releases have been produced. SUMMARY The Apache Jakarta Commons project is a unique repository of open source Java components. As you take advantage of the Commons, keep in mind the hard work that has gone into developing and maintaining this software. The Apache license represents one of the least selfish approaches toward software in the world, and this is repaid in tremendous goodwill and respect. If you can, con- sider donating some of your own time to this project. Download the source via CVS, participate on the mailing lists, and contribute code. Learn, listen, and comment with grace, and you will be repaid many times over. Iverson_ch14.qxd 1/17/05 2:42 PM Page 200 Iverson_appA.qxd 1/17/05 2:37 PM Page 201 A P P E N D I X A Lang Reference This appendix provides a summary of the javadoc for a subset of the most com- monly used portions of the Commons Lang package. This includes all of the classes in the org.apache.commons.lang.* package and org.apache.commons.lang .time.* package. ORG.APACHE.COMMONS.LANG ArrayUtils Operations on arrays, primitive arrays (like int[]) and primitive wrapper arrays (like Integer[]). BitField Operations on bit-mapped fields. BooleanUtils Operations on boolean primitives and Boolean objects. CharRange A contiguous range of characters, optionally negated. CharSet A set of characters. CharSetUtils Operations on CharSets. 201 Iverson_appA.qxd 1/17/05 2:37 PM Page 202 202 Lang Reference Appendix A ClassUtils Operates on classes without using reflection. ObjectUtils Operations on Object. ObjectUtils.Null Class used as a null placeholder where null has another meaning. RandomStringUtils Operations for random strings. SerializationUtils Assists with the serialization process and performs additional functionality based on serialization. StringEscapeUtils Escapes and unescapes strings for Java, Java Script, HTML, XML, and SQL. StringUtils Operations on String that are null safe. SystemUtils Helpers for java.lang.System. Validate Assists in validating arguments. WordUtils Operations on strings that contain words. ORG.APACHE.COMMONS.LANG.ARRAYUTILS Operations on arrays, primitive arrays (like int[]), and primitive wrapper arrays (like Integer[]). Iverson_appA.qxd 1/17/05 2:37 PM Page 203 org.apache.commons.lang.ArrayUtils 203 This class tries to handle null input gracefully. An exception will not be thrown for a null array input. However, an object array that contains a null element may throw an exception. Each method documents its behavior. public static final java.lang.Object[] EMPTY_OBJECT_ARRAY An empty immutable Object array. public static final java.lang.Class[] EMPTY_CLASS_ARRAY An empty immutable Class array. public static final java.lang.String[] EMPTY_STRING_ARRAY An empty immutable String array. public static final long[] EMPTY_LONG_ARRAY An empty immutable long array. public static final java.lang.Long[] EMPTY_LONG_OBJECT_ARRAY An empty immutable Long array. public static final int[] EMPTY_INT_ARRAY An empty immutable int array. public static final java.lang.Integer[] EMPTY_INTEGER_OBJECT_ARRAY An empty immutable Integer array. public static final short[] EMPTY_SHORT_ARRAY An empty immutable short array. public static final java.lang.Short[] EMPTY_SHORT_OBJECT_ARRAY An empty immutable Short array. public static final byte[] EMPTY_BYTE_ARRAY An empty immutable byte array. public static final java.lang.Byte[] EMPTY_BYTE_OBJECT_ARRAY An empty immutable Byte array. public static final double[] EMPTY_DOUBLE_ARRAY Iverson_appA.qxd 1/17/05 2:37 PM Page 204 204 Lang Reference Appendix A An empty immutable double array. public static final java.lang.Double[] EMPTY_DOUBLE_OBJECT_ARRAY An empty immutable Double array. public static final float[] EMPTY_FLOAT_ARRAY An empty immutable float array. static final java.lang.Float[] EMPTY_FLOAT_OBJECT_ARRAY An empty immutable Float array. public static final boolean[] EMPTY_BOOLEAN_ARRAY An empty immutable boolean array. public static final java.lang.Boolean[] EMPTY_BOOLEAN_OBJECT_ARRAY An empty immutable Boolean array. public static final char[] EMPTY_CHAR_ARRAY An empty immutable char array. public static final java.lang.Character[] EMPTY_CHARACTER_OBJECT_ARRAY An empty immutable Character array. Constructor Detail public ArrayUtils() ArrayUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ArrayUtils.clone (new int[] {2}). This con- structor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String toString(java.lang.Object array) Outputs an array as a String, treating null as an empty array. Multi- dimensional arrays are handled correctly, including multi-dimensional primi- tive arrays. The format is that of Java source code, for example {a,b}. Parameters: array—the array to get a toString for, may be null Returns: a String representation of the array, '{}' if null array input public static java.lang.String toString(java.lang.Object array, java.lang.String stringIfNull) Iverson_appA.qxd 1/17/05 2:37 PM Page 205 org.apache.commons.lang.ArrayUtils 205 Outputs an array as a String handling nulls. Multi-dimensional arrays are handled correctly, including multi-dimensional primitive arrays. The format is that of Java source code, for example {a,b}. Parameters: array—the array to get a toString for, may be null stringIfNull—the String to return if the array is null Returns: a String representation of the array public static int hashCode(java.lang.Object array) Get a hashCode for an array handling multi-dimensional arrays correctly. Multi-dimensional primitive arrays are also handled correctly by this method. Parameters: array—the array to get a hashCode for, may be null Returns: a hashCode for the array, zero if null array input public static boolean isEquals(java.lang.Object array1, java.lang.Object array2) Compares two arrays, using equals(), handling multi-dimensional arrays cor- rectly. Multi-dimensional primitive arrays are also handled correctly by this method. Parameters: array1—the array to get a hashCode for, may be null array2—the array to get a hashCode for, may be null Returns: true if the arrays are equal public static java.util.Map toMap(java.lang.Object[] array) Converts the given array into a Map. Each element of the array must be either a Map.Entry or an array, containing at least two elements, where the first ele- ment is used as key and the second as value. This method can be used to initialize: // Create a Map mapping colors. Map colorMap = MapUtils.toMap(new String[][] {{ {"RED", "#FF0000"}, {"GREEN", "#00FF00"}, {"BLUE", "#0000FF"}}); This method returns null if null array input. Parameters: array—an array whose elements are either a Map.Entry or an array containing at least two elements, may be null Returns: a Map that was created from the array Throws: java.lang.IllegalArgumentException—if one element of this array is itself an array containing less then two elements java.lang.IllegalArgumentException—if the array contains elements other than Map.Entry and an array public static java.lang.Object[] clone(java.lang.Object[] array) Iverson_appA.qxd 1/17/05 2:37 PM Page 206 206 Lang Reference Appendix A Shallow clones an array returning a typecast result and handling null. The objects in the array are not cloned; thus there is no special handling for multi- dimensional arrays. This method returns null if null array input. Parameters: array—the array to shallow clone, may be null Returns: the cloned array, null if null input public static long[] clone(long[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static int[] clone(int[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static short[] clone(short[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static char[] clone(char[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static byte[] clone(byte[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static double[] clone(double[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Iverson_appA.qxd 1/17/05 2:37 PM Page 207 org.apache.commons.lang.ArrayUtils 207 Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static float[] clone(float[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static boolean[] clone(boolean[] array) Clones an array returning a typecast result and handling null. This method returns null if null array input. Parameters: array—the array to clone, may be null Returns: the cloned array, null if null input public static boolean isSameLength(java.lang.Object[] array1, java.lang.Object[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Any multi-dimensional aspects of the arrays are ignored. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(long[] array1, long[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(int[] array1, int[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(short[] array1, short[] array2) Iverson_appA.qxd 1/17/05 2:37 PM Page 208 208 Lang Reference Appendix A Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(char[] array1, char[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(byte[] array1, byte[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(double[] array1, double[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(float[] array1, float[] array2) Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameLength(boolean[] array1, boolean[] array2) Iverson_appA.qxd 1/17/05 2:37 PM Page 209 org.apache.commons.lang.ArrayUtils 209 Checks whether two arrays are the same length, treating null arrays as length 0. Parameters: array1—the first array, may be null array2—the second array, may be null Returns: true if length of arrays matches, treating null as an empty array public static boolean isSameType(java.lang.Object array1, java.lang.Object array2) Checks whether two arrays are the same type, taking into account multi- dimensional arrays. Parameters: array1—the first array, must not be null array2—the second array, must not be null Returns: true if type of arrays matches Throws: java.lang.IllegalArgumentException—if either array is null public static void reverse(java.lang.Object[] array) Reverses the order of the given array. There is no special handling for multi- dimensional arrays. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(long[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(int[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(short[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(char[] array) Reverses the order of the given array. This method does nothing if null array input. Iverson_appA.qxd 1/17/05 2:37 PM Page 210 210 Lang Reference Appendix A Parameters: array—the array to reverse, may be null public static void reverse(byte[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(double[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(float[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static void reverse(boolean[] array) Reverses the order of the given array. This method does nothing if null array input. Parameters: array—the array to reverse, may be null public static int indexOf(java.lang.Object[] array, java.lang.Object objectToFind) Find the index of the given object in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null objectToFind—the object to find, may be null Returns: the index of the object within the array, -1 if not found or null array input public static int indexOf(java.lang.Object[] array, java.lang.Object objectToFind, int startIndex) Find the index of the given object in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null objectToFind—the object to find, may be null startIndex—the index to start searching at Iverson_appA.qxd 1/17/05 2:37 PM Page 211 org.apache.commons.lang.ArrayUtils 211 Returns: the index of the object within the array starting at the index, -1 if not found or null array input public static int lastIndexOf(java.lang.Object[] array, java.lang.Object objectToFind) Find the last index of the given object within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null objectToFind—the object to find, may be null Returns: the last index of the object within the array, -1 if not found or null array input public static int lastIndexOf(java.lang.Object[] array, java.lang.Object objectToFind, int startIndex) Find the last index of the given object in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null objectToFind—the object to find, may be null startIndex—the start index to traverse backward from Returns: the last index of the object within the array, -1 if not found or null array input public static boolean contains(java.lang.Object[] array, java.lang.Object objectToFind) Checks if the object is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through objectToFind—the object to find Returns: true if the array contains the object public static int indexOf(long[] array, long valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(long[] array, long valueToFind, int startIndex) Iverson_appA.qxd 1/17/05 2:37 PM Page 212 212 Lang Reference Appendix A Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(long[] array, long valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(long[] array, long valueToFind, int startIndex) Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(long[] array, long valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static int indexOf(int[] array, int valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Iverson_appA.qxd 1/17/05 2:37 PM Page 213 org.apache.commons.lang.ArrayUtils 213 Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(int[] array, int valueToFind, int startIndex) Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(int[] array, int valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(int[] array, int valueToFind, int startIndex) Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(int[] array, int valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through Iverson_appA.qxd 1/17/05 2:37 PM Page 214 214 Lang Reference Appendix A valueToFind—the value to find Returns: true if the array contains the object public static int indexOf(short[] array, short valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(short[] array, short valueToFind, int startIndex) Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(short[] array, short valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(short[] array, short valueToFind, int startIndex) Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Iverson_appA.qxd 1/17/05 2:37 PM Page 215 org.apache.commons.lang.ArrayUtils 215 Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(short[] array, short valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static int indexOf(byte[] array, byte valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(byte[] array, byte valueToFind, int startIndex) Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(byte[] array, byte valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(byte[] array, byte valueToFind, int startIndex) Iverson_appA.qxd 1/17/05 2:37 PM Page 216 216 Lang Reference Appendix A Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(byte[] array, byte valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static int indexOf(double[] array, double valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(double[] array, double valueToFind, double tolerance) Find the index of the given value within a given tolerance in the array. This method will return the index of the first value which falls between the region defined by valueToFind - tolerance and valueToFind + tolerance. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find tolerance—tolerance of the search Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(double[] array, double valueToFind, int startIndex) Iverson_appA.qxd 1/17/05 2:37 PM Page 217 org.apache.commons.lang.ArrayUtils 217 Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(double[] array, double valueToFind, int startIndex, double tolerance) Find the index of the given value in the array starting at the given index. This method will return the index of the first value which falls between the region defined by valueToFind - tolerance and valueToFind + tolerance. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at tolerance—tolerance of the search Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(double[] array, double valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(double[] array, double valueToFind, double tolerance) Find the last index of the given value within a given tolerance in the array. This method will return the index of the last value which falls between the region defined by valueToFind - tolerance and valueToFind + tolerance. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null Iverson_appA.qxd 1/17/05 2:37 PM Page 218 218 Lang Reference Appendix A valueToFind—the value to find tolerance—tolerance of the search Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(double[] array, double valueToFind, int startIndex) Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(double[] array, double valueToFind, int startIndex, double tolerance) Find the last index of the given value in the array starting at the given index. This method will return the index of the last value which falls between the region defined by valueToFind - tolerance and valueToFind + tolerance. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from tolerance—search for value within plus/minus this amount Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(double[] array, double valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static boolean contains(double[] array, double valueToFind, double tolerance) Iverson_appA.qxd 1/17/05 2:37 PM Page 219 org.apache.commons.lang.ArrayUtils 219 Checks if a value falling within the given tolerance is in the given array. If the array contains a value within the inclusive range defined by (value - tolerance) to (value + tolerance). The method returns false if a null array is passed in. Parameters: array—the array to search valueToFind—the value to find tolerance—the array contains the tolerance of the search Returns: true if value falling within tolerance is in array public static int indexOf(float[] array, float valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(float[] array, float valueToFind, int startIndex) Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(float[] array, float valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(float[] array, float valueToFind, int startIndex) Iverson_appA.qxd 1/17/05 2:37 PM Page 220 220 Lang Reference Appendix A Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(float[] array, float valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static int indexOf(boolean[] array, boolean valueToFind) Find the index of the given value in the array. This method returns -1 if null array input. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find Returns: the index of the value within the array, -1 if not found or null array input public static int indexOf(boolean[] array, boolean valueToFind, int startIndex) Find the index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex is treated as zero. A startIndex larger than the array length will return -1. Parameters: array—the array to search through for the object, may be null valueToFind—the value to find startIndex—the index to start searching at Returns: the index of the value within the array, -1 if not found or null array input public static int lastIndexOf(boolean[] array, boolean valueToFind) Find the last index of the given value within the array. This method returns -1 if null array input. Iverson_appA.qxd 1/17/05 2:37 PM Page 221 org.apache.commons.lang.ArrayUtils 221 Parameters: array—the array to traverse backward looking for the object, may be null valueToFind—the object to find Returns: the last index of the value within the array, -1 if not found or null array input public static int lastIndexOf(boolean[] array, boolean valueToFind, int startIndex) Find the last index of the given value in the array starting at the given index. This method returns -1 if null array input. A negative startIndex will return -1. A startIndex larger than the array length will search from the end of the array. Parameters: array—the array to traverse looking for the object, may be null valueToFind—the value to find startIndex—the start index to traverse backward from Returns: the last index of the value within the array, -1 if not found or null array input public static boolean contains(boolean[] array, boolean valueToFind) Checks if the value is in the given array. The method returns false if a null array is passed in. Parameters: array—the array to search through valueToFind—the value to find Returns: true if the array contains the object public static long[] toPrimitive(java.lang.Long[] array) Converts an array of object Longs to primitives. This method returns null if null array input. Parameters: array—a Long array, may be null Returns: a long array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static long[] toPrimitive(java.lang.Long[] array, long valueForNull) Converts an array of object Long to primitives handling null. This method returns null if null array input. Parameters: array—a Long array, may be null valueForNull—the value to insert if null found Returns: a long array, null if null array input public static java.lang.Long[] toObject(long[] array) Iverson_appA.qxd 1/17/05 2:37 PM Page 222 222 Lang Reference Appendix A Converts an array of primitive longs to objects. This method returns null if null array input. Parameters: array—a long array Returns: a Long array, null if null array input public static int[] toPrimitive(java.lang.Integer[] array) Converts an array of object Integers to primitives. This method returns null if null array input. Parameters: array—an Integer array, may be null Returns: an int array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static int[] toPrimitive(java.lang.Integer[] array, int valueForNull) Converts an array of object Integer to primitives handling null. This method returns null if null array input. Parameters: array—an Integer array, may be null valueForNull—the value to insert if null found Returns: an int array, null if null array input public static java.lang.Integer[] toObject(int[] array) Converts an array of primitive ints to objects. This method returns null if null array input. Parameters: array—an int array Returns: an Integer array, null if null array input public static short[] toPrimitive(java.lang.Short[] array) Converts an array of object Shorts to primitives. This method returns null if null array input. Parameters: array—a Short array, may be null Returns: a byte array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static short[] toPrimitive(java.lang.Short[] array, short valueForNull) Converts an array of object Short to primitives handling null. This method returns null if null array input. Parameters: array—a Short array, may be null valueForNull—the value to insert if null found Returns: a byte array, null if null array input Iverson_appA.qxd 1/17/05 2:37 PM Page 223 org.apache.commons.lang.ArrayUtils 223 public static java.lang.Short[] toObject(short[] array) Converts an array of primitive shorts to objects. This method returns null if null array input. Parameters: array—a short array Returns: a Short array, null if null array input public static byte[] toPrimitive(java.lang.Byte[] array) Converts an array of object Bytes to primitives. This method returns null if null array input. Parameters: array—a Byte array, may be null Returns: a byte array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static byte[] toPrimitive(java.lang.Byte[] array, byte valueForNull) Converts an array of object Bytes to primitives handling null. This method returns null if null array input. Parameters: array—a Byte array, may be null valueForNull—the value to insert if null found Returns: a byte array, null if null array input public static java.lang.Byte[] toObject(byte[] array) Converts an array of primitive bytes to objects. This method returns null if null array input. Parameters: array—a byte array Returns: a Byte array, null if null array input public static double[] toPrimitive(java.lang.Double[] array) Converts an array of object Doubles to primitives. This method returns null if null array input. Parameters: array—a Double array, may be null Returns: a double array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static double[] toPrimitive(java.lang.Double[] array, double valueForNull) Converts an array of object Doubles to primitives handling null. This method returns null if null array input. Parameters: array—a Double array, may be null valueForNull—the value to insert if null found Iverson_appA.qxd 1/17/05 2:37 PM Page 224 224 Lang Reference Appendix A Returns: a double array, null if null array input public static java.lang.Double[] toObject(double[] array) Converts an array of primitive doubles to objects. This method returns null if null array input. Parameters: array—a double array Returns: a Double array, null if null array input public static float[] toPrimitive(java.lang.Float[] array) Converts an array of object Floats to primitives. This method returns null if null array input. Parameters: array—a Float array, may be null Returns: a float array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static float[] toPrimitive(java.lang.Float[] array, float valueForNull) Converts an array of object Floats to primitives handling null. This method returns null if null array input. Parameters: array—a Float array, may be null valueForNull—the value to insert if null found Returns: a float array, null if null array input public static java.lang.Float[] toObject(float[] array) Converts an array of primitive floats to objects. This method returns null if null array input. Parameters: array—a float array Returns: a Float array, null if null array input public static boolean[] toPrimitive(java.lang.Boolean[] array) Converts an array of object Booleans to primitives. This method returns null if null array input. Parameters: array—a Boolean array, may be null Returns: a boolean array, null if null array input Throws: java.lang.NullPointerException—if array content is null public static boolean[] toPrimitive(java.lang.Boolean[] array, boolean valueForNull) Converts an array of object Booleans to primitives handling null. This method returns null if null array input. Iverson_appA.qxd 1/17/05 2:37 PM Page 225 org.apache.commons.lang.BitField 225 Parameters: array—a Boolean array, may be null valueForNull—the value to insert if null found Returns: a boolean array, null if null array input public static java.lang.Boolean[] toObject(boolean[] array) Converts an array of primitive booleans to objects. This method returns null if null array input. Parameters: array—a boolean array Returns: a Boolean array, null if null array input ORG.APACHE.COMMONS.LANG.BITFIELD Operations on bit-mapped fields. Constructor Detail public BitField(int mask) Creates a BitField instance. Parameters: mask—the mask specifying which bits apply to this BitField. Bits that are set in this mask are the bits that this BitField operates on Method Detail public int getValue(int holder) Obtains the value for the specified BitField, appropriately shifted right. Many users of a BitField will want to treat the specified bits as an int value, and will not want to be aware that the value is stored as a BitField (and so shifted left so many bits). Parameters: holder—the int data containing the bits we’re interested in Returns: the selected bits, shifted right appropriately See Also: setValue(int, int) public short getShortValue(short holder) Obtains the value for the specified BitField, appropriately shifted right, as a short. Many users of a BitField will want to treat the specified bits as an int value, and will not want to be aware that the value is stored as a BitField (and so shifted left so many bits). Parameters: holder—the short data containing the bits we’re inter- ested in Iverson_appA.qxd 1/17/05 2:37 PM Page 226 226 Lang Reference Appendix A Returns: the selected bits, shifted right appropriately See Also: setShortValue(short, short) public int getRawValue(int holder) Obtains the value for the specified BitField, unshifted. Parameters: holder—the int data containing the bits we’re interested in Returns: the selected bits public short getShortRawValue(short holder) Obtains the value for the specified BitField, unshifted. Parameters: holder—the short data containing the bits we’re inter- ested in Returns: the selected bits public boolean isSet(int holder) Returns whether the field is set or not. This is most commonly used for a single-bit field, which is often used to represent a boolean value; the result of using it for a multi-bit field is to deter- mine whether *any* of its bits are set. Parameters: holder—the int data containing the bits we’re interested in Returns: true if any of the bits are set, else false public boolean isAllSet(int holder) Returns whether all of the bits are set or not. This is a stricter test than isSet(int), in that all of the bits in a multi-bit set must be set for this method to return true. Parameters: holder—the int data containing the bits we’re interested in Returns: true if all of the bits are set, else false public int setValue(int holder, int value) Replaces the bits with new values. Parameters: holder—the int data containing the bits we’re interested in value—the new value for the specified bits Returns: the value of holder with the bits from the value parameter replacing the old bits See Also: getValue(int) public short setShortValue(short holder, short value) Replaces the bits with new values. Iverson_appA.qxd 1/17/05 2:37 PM Page 227 org.apache.commons.lang.BitField 227 Parameters: holder—the short data containing the bits we’re inter- ested in value—the new value for the specified bits Returns: the value of holder with the bits from the value parameter replacing the old bits See Also: getShortValue(short) public int clear(int holder) Clears the bits. Parameters: holder—the int data containing the bits we’re interested in Returns: the value of holder with the specified bits cleared (set to 0) public short clearShort(short holder) Clears the bits. Parameters: holder—the short data containing the bits we’re inter- ested in Returns: the value of holder with the specified bits cleared (set to 0) public byte clearByte(byte holder) Clears the bits. Parameters: holder—the byte data containing the bits we’re interested in Returns: the value of holder with the specified bits cleared (set to 0) public int set(int holder) Sets the bits. Parameters: holder—the int data containing the bits we’re interested in Returns: the value of holder with the specified bits set to 1 public short setShort(short holder) Sets the bits. Parameters: holder—the short data containing the bits we’re inter- ested in Returns: the value of holder with the specified bits set to 1 public byte setByte(byte holder) Sets the bits. Parameters: holder—the byte data containing the bits we’re interested in Returns: the value of holder with the specified bits set to 1 public int setBoolean(int holder, boolean flag) Iverson_appA.qxd 1/17/05 2:37 PM Page 228 228 Lang Reference Appendix A Sets a boolean BitField. Parameters: holder—the int data containing the bits we’re interested in flag—indicating whether to set or clear the bits Returns: the value of holder with the specified bits set or cleared public short setShortBoolean(short holder, boolean flag) Sets a boolean BitField. Parameters: holder—the short data containing the bits we’re inter- ested in flag—indicating whether to set or clear the bits Returns: the value of holder with the specified bits set or cleared public byte setByteBoolean(byte holder, boolean flag) Sets a boolean BitField. Parameters: holder—the byte data containing the bits we’re interested in flag—indicating whether to set or clear the bits Returns: the value of holder with the specified bits set or cleared ORG.APACHE.COMMONS.LANG.BOOLEANUTILS java.lang.Object org.apache.commons.lang.BooleanUtils Operations on boolean primitives and Boolean objects. This class tries to handle null input gracefully. An exception will not be thrown for a null input. Each method documents its behavior in more detail. Constructor Detail public BooleanUtils() BooleanUtils instances should NOT be constructed in standard programming. Instead, the class should be used as BooleanUtils.toBooleanObject(true);. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.Boolean negate(java.lang.Boolean bool) Negates the specified boolean. If null is passed in, null will be returned. Parameters: bool—the Boolean to negate, may be null Iverson_appA.qxd 1/17/05 2:37 PM Page 229 org.apache.commons.lang.BooleanUtils 229 Returns: the negated Boolean, or null if null input public static java.lang.Boolean toBooleanObject(boolean bool) Boolean factory that avoids creating new Boolean objecs all the time. This method was added to JDK1.4 but is available here for earlier JDKs. Parameters: bool—the boolean to convert Returns: Boolean.TRUE or Boolean.FALSE as appropriate public static boolean toBoolean(java.lang.Boolean bool) Converts a Boolean to a boolean handling null by returning false. Parameters: bool—the boolean to convert Returns: true or false, null returns false public static boolean toBooleanDefaultIfNull(java.lang.Boolean bool, boolean valueIfNull) Converts a Boolean to a boolean handling null. Parameters: bool—the boolean to convert valueIfNull—the boolean value to return if null Returns: true or false public static boolean toBoolean(int value) Converts an int to a boolean using the convention that zero is false. Parameters: value—the int to convert Returns: true if non-zero, false if zero public static java.lang.Boolean toBooleanObject(int value) Converts an int to a Boolean using the convention that zero is false. Parameters: value—the int to convert Returns: Boolean.TRUE if non-zero, Boolean.FALSE if zero, null if null public static java.lang.Boolean toBooleanObject(java.lang.Integer value) Converts an Integer to a Boolean using the convention that zero is false. null will be converted to null. Parameters: value—the Integer to convert Returns: Boolean.TRUE if non-zero, Boolean.FALSE if zero, null if null input public static boolean toBoolean(int value, int trueValue, int falseValue) Iverson_appA.qxd 1/17/05 2:37 PM Page 230 230 Lang Reference Appendix A Converts an int to a boolean specifying the conversion values. Parameters: value—the Integer to convert trueValue—the value to match for true falseValue—the value to match for false Returns: true or false Throws: java.lang.IllegalArgumentException—if no match public static boolean toBoolean(java.lang.Integer value, java.lang.Integer trueValue, java.lang.Integer falseValue) Converts an Integer to a boolean specifying the conversion values. Parameters: value—the Integer to convert trueValue—the value to match for true, may be null falseValue—the value to match for false, may be null Returns: true or false Throws: java.lang.IllegalArgumentException—if no match public static java.lang.Boolean toBooleanObject(int value, int trueValue, int falseValue, int nullValue) Converts an int to a Boolean specifying the conversion values. Parameters: value—the Integer to convert trueValue—the value to match for true falseValue—the value to match for false nullValue—the value to match for null Returns: Boolean.TRUE, Boolean.FALSE, or null Throws: java.lang.IllegalArgumentException—if no match public static java.lang.Boolean toBooleanObject(java.lang.Integer value, java.lang.Integer trueValue, java.lang.Integer falseValue, java.lang.Integer nullValue) Converts an Integer to a Boolean specifying the conversion values. Parameters: value—the Integer to convert trueValue—the value to match for true, may be null falseValue—the value to match for false, may be null nullValue—the value to match for null, may be null Returns: Boolean.TRUE, Boolean.FALSE, or null Throws: java.lang.IllegalArgumentException—if no match public static int toInteger(boolean bool) Converts a boolean to an int using the convention that zero is false. Parameters: bool—the boolean to convert Returns: one if true, zero if false public static java.lang.Integer toIntegerObject(boolean bool) Iverson_appA.qxd 1/17/05 2:37 PM Page 231 org.apache.commons.lang.BooleanUtils 231 Converts a boolean to an Integer using the convention that zero is false. Parameters: bool—the Boolean to convert Returns: one if true, zero if false public static java.lang.Integer toIntegerObject(java.lang.Boolean bool) Converts a Boolean to a Integer using the convention that zero is false. null will be converted to null. Parameters: bool—the Boolean to convert Returns: one if Boolean.TRUE, zero if Boolean.FALSE, null if null public static int toInteger(boolean bool, int trueValue, int falseValue) Converts a boolean to an int specifying the conversion values. Parameters: bool—the Boolean to convert trueValue—the value to return if true falseValue—the value to return if false Returns: the appropriate value public static int toInteger(java.lang.Boolean bool, int trueValue, int falseValue, int nullValue) Converts a Boolean to an int specifying the conversion values. Parameters: bool—the Boolean to convert trueValue—the value to return if true falseValue—the value to return if false nullValue—the value to return if null Returns: the appropriate value public static java.lang.Integer toIntegerObject(boolean bool, java.lang.Integer trueValue, java.lang.Integer falseValue) Converts a boolean to an Integer specifying the conversion values. Parameters: bool—the Boolean to convert trueValue—the value to return if true, may be null falseValue—the value to return if false, may be null Returns: the appropriate value public static java.lang.Integer toIntegerObject(java.lang.Boolean bool, java.lang.Integer trueValue, java.lang.Integer falseValue, java.lang.Integer nullValue) Converts a Boolean to an Integer specifying the conversion values. Parameters: bool—the Boolean to convert trueValue—the value to return if true, may be null Iverson_appA.qxd 1/17/05 2:37 PM Page 232 232 Lang Reference Appendix A falseValue—the value to return if false, may be null nullValue—the value to return if null, may be null Returns: the appropriate value public static java.lang.Boolean toBooleanObject(java.lang.String str) Converts a String to a Boolean. 'true', 'on' or 'yes' (case insensitive) will return true. 'false', 'off ' or 'no' (case insensitive) will return false. Otherwise, null is returned. Parameters: str—the String to check Returns: the Boolean value of the string, null if no match or null input public static java.lang.Boolean toBooleanObject(java.lang.String str, java.lang.String trueString, java.lang.String falseString, java.lang.String nullString) Converts a String to a Boolean throwing an exception if no match. Parameters: str—the String to check trueString—the String to match for true (case sensitive), may be null falseString—the String to match for false (case sensitive), may be null nullString—the String to match for null (case sensitive), may be null Returns: the Boolean value of the string, null if no match or null input public static boolean toBoolean(java.lang.String str) Converts a String to a boolean. 'true', 'on' or 'yes' (case insensitive) will return true. Otherwise, false is returned. Parameters: str—the String to check Returns: the boolean value of the string, false if no match public static boolean toBoolean(java.lang.String str, java.lang.String trueString, java.lang.String falseString) Converts a String to a Boolean throwing an exception if no match found. null is returned if there is no match. Parameters: str—the String to check trueString—the String to match for true (case sensitive), may be null falseString—the String to match for false (case sensitive), may be null Returns: the boolean value of the string Throws: java.lang.IllegalArgumentException—if the String doesn’t match public static java.lang.String toStringTrueFalse(java.lang.Boolean bool) Iverson_appA.qxd 1/17/05 2:37 PM Page 233 org.apache.commons.lang.BooleanUtils 233 Converts a Boolean to a String returning 'true', 'false', or null. Parameters: bool—the Boolean to check Returns: 'true', 'false', or null public static java.lang.String toStringOnOff(java.lang.Boolean bool) Converts a Boolean to a String returning 'on', 'off ', or null. Parameters: bool—the Boolean to check Returns: 'on', 'off', or null public static java.lang.String toStringYesNo(java.lang.Boolean bool) Converts a Boolean to a String returning 'yes', 'no', or null. Parameters: bool—the Boolean to check Returns: 'yes', 'no', or null public static java.lang.String toString(java.lang.Boolean bool, java.lang.String trueString, java.lang.String falseString, java.lang.String nullString) Converts a Boolean to a String returning one of the input Strings. Parameters: bool—the Boolean to check trueString—the String to return if true, may be null falseString—the String to return if false, may be null nullString—the String to return if null, may be null Returns: one of the three input Strings public static java.lang.String toStringTrueFalse(boolean bool) Converts a boolean to a String returning 'true' or 'false'. Parameters: bool—the Boolean to check Returns: 'true', 'false', or null public static java.lang.String toStringOnOff(boolean bool) Converts a boolean to a String returning 'on' or 'off '. Parameters: bool—the Boolean to check Returns: 'on', 'off', or null public static java.lang.String toStringYesNo(boolean bool) Converts a boolean to a String returning 'yes' or 'no'. Parameters: bool—the Boolean to check Returns: 'yes', 'no', or null Iverson_appA.qxd 1/17/05 2:37 PM Page 234 234 Lang Reference Appendix A public static java.lang.String toString(boolean bool, java.lang.String trueString, java.lang.String falseString) Converts a boolean to a String returning one of the input Strings. Parameters: bool—the Boolean to check trueString—the String to return if true, may be null falseString—the String to return if false, may be null Returns: one of the two input Strings public static boolean xor(boolean[] array) Performs an xor on a set of booleans. Parameters: array—an array of booleans Returns: true if the xor is successful. Throws: java.lang.IllegalArgumentException—if array is null java.lang.IllegalArgumentException—if array is empty. public static java.lang.Boolean xor(java.lang.Boolean[] array) Performs an xor on an array of Booleans. Parameters: array—an array of Booleans Returns: true if the xor is successful Throws: java.lang.IllegalArgumentException—if array is null java.lang.IllegalArgumentException—if array is empty. java.lang.IllegalArgumentException—if array contains a null org.apache.commons.lang.CharRange public final class CharRange implements java.io.Serializable A contiguous range of characters, optionally negated. Instances are immutable. Constructor Detail public CharRange(char ch) Constructs a CharRange over a single character. Parameters: ch—only character in this range public CharRange(char ch, boolean negated) Constructs a CharRange over a single character, optionally negating the range. A negated range includes everything except the specified char. Parameters: ch—only character in this range Iverson_appA.qxd 1/17/05 2:37 PM Page 235 org.apache.commons.lang.BooleanUtils 235 negated—true to express everything except the range public CharRange(char start, char end) Constructs a CharRange over a set of characters. Parameters: start—first character, inclusive, in this range end—last character, inclusive, in this range public CharRange(char start, char end, boolean negated) Constructs a CharRange over a set of characters, optionally negating the range. A negated range includes everything except that defined by the start and end characters. If start and end are in the wrong order, they are reversed. Thus a-e is the same as e-a. Parameters: start—first character, inclusive, in this range end—last character, inclusive, in this range negated—true to express everything except the range Method Detail public char getStart() Gets the start character for this character range. Returns: the start char (inclusive) public char getEnd() Gets the end character for this character range. Returns: the end char (inclusive) public boolean isNegated() Is this CharRange negated. A negated range includes everything except that defined by the start and end characters. Returns: true is negated public boolean contains(char ch) Is the character specified contained in this range. Parameters: ch—the character to check Returns: true if this range contains the input character public boolean contains(CharRange range) Are all the characters of the passed in range contained in this range. Parameters: range—the range to check against Iverson_appA.qxd 1/17/05 2:37 PM Page 236 236 Lang Reference Appendix A Returns: true if this range entirely contains the input range Throws: java.lang.IllegalArgumentException—if null input public boolean equals(java.lang.Object obj) Compares two CharRange objects, returning true if they represent exactly the same range of characters defined in the same way. Parameters: obj—the object to compare to Returns: true if equal public int hashCode() Gets a hashCode compatable with the equals method. Returns: a suitable hashCode public java.lang.String toString() Gets a string representation of the character range. Returns: string representation of this range org.apache.commons.lang.CharSet public class CharSet implements java.io.Serializable A set of characters. Instances are immutable, but instances of subclasses may not be. Field Summary public static final CharSet EMPTY A CharSet defining no characters. public static final CharSet ASCII_ALPHA A CharSet defining ASCII alphabetic characters "a-zA-Z". public static final CharSet ASCII_ALPHA_LOWER A CharSet defining ASCII alphabetic characters "a-z". public static final CharSet ASCII_ALPHA_UPPER A CharSet defining ASCII alphabetic characters "A-Z". public static final CharSet ASCII_NUMERIC A CharSet defining ASCII alphabetic characters "0-9". Iverson_appA.qxd 1/17/05 2:37 PM Page 237 org.apache.commons.lang.BooleanUtils 237 Method Detail public static CharSet getInstance(java.lang.String setStr) Factory method to create a new CharSet using a special syntax. ☞ null or empty string (" ")—set containing no characters ☞ Single character, such as "a"—set containing just that character ☞ Multi character, such as "a-e"—set containing characters from one char- acter to the other ☞ Negated, such as "^a" or "^a-e"—set containing all characters except those defined ☞ Combinations, such as "abe-g"—set containing all the characters from the individual sets The matching order is: 1. Negated multi character range, such as "^a-e" 2. Ordinary multi character range, such as "a-e" 3. Negated single character, such as "^a" 4. Ordinary single character, such as "a" Matching works left to right. Once a match is found the search starts again from the next character. If the same range is defined twice using the same syntax, only one range will be kept. Thus, "a-ca-c" creates only one range of "a-c". If the start and end of a range are in the wrong order, they are reversed. Thus "a-e" is the same as "e-a". As a result, "a-ee-a" would create only one range, as the "a-e" and "e-a" are the same. The set of characters represented is the union of the specified ranges. All CharSet objects returned by this method will be immutable. Parameters: setStr—the String describing the set, may be null Returns: a CharSet instance public CharRange[] getCharRanges() Gets the internal set as an array of CharRange objects. Returns: an array of immutable CharRange objects public boolean contains(char ch) Does the CharSet contain the specified character ch. Parameters: ch—the character to check for Returns: true if the set contains the characters public boolean equals(java.lang.Object obj) Compares two CharSet objects, returning true if they represent exactly the same set of characters defined in the same way. Iverson_appA.qxd 1/17/05 2:37 PM Page 238 238 Lang Reference Appendix A The two sets abc and a-c are not equal according to this method. Parameters: obj—the object to compare to Returns: true if equal public int hashCode() Gets a hashCode compatible with the equals method. Returns: a suitable hashCode public java.lang.String toString() Gets a string representation of the set. Returns: string representation of the set org.apache.commons.lang.CharSetUtils This class handles null input gracefully. An exception will not be thrown for a null input. Each method documents its behavior in more detail. Constructor Detail public CharSetUtils() CharSetUtils instances should NOT be constructed in standard programming. Instead, the class should be used as CharSetUtils.evaluateSet(null);. This con- structor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String squeeze(java.lang.String str, java.lang.String set) Squeezes any repetitions of a character that is mentioned in the supplied set. CharSetUtils.squeeze(null, *) = null CharSetUtils.squeeze("", *) = "" CharSetUtils.squeeze(*, null) = * CharSetUtils.squeeze(*, "") = * CharSetUtils.squeeze("hello", "k-p") = "helo" CharSetUtils.squeeze("hello", "a-e") = "hello" Parameters: str—the string to squeeze, may be null set—the character set to use for manipulation, may be null Returns: modified String, null if null string input See Also: for set-syntax. public static java.lang.String squeeze(java.lang.String str, java.lang.String[] set) Iverson_appA.qxd 1/17/05 2:37 PM Page 239 org.apache.commons.lang.BooleanUtils 239 Squeezes any repetitions of a character that is mentioned in the supplied set. An example is: squeeze("hello", {"el"}) => "helo" Parameters: str—the string to squeeze, may be null set—the character set to use for manipulation, may be null Returns: modified String, null if null string input See Also: for set-syntax. public static int count(java.lang.String str, java.lang.String set) Takes an argument in set-syntax, see evaluateSet, and returns the number of characters present in the specified string. CharSetUtils.count(null, *) = 0 CharSetUtils.count("", *) = 0 CharSetUtils.count(*, null) = 0 CharSetUtils.count(*, "") = 0 CharSetUtils.count("hello", "k-p") = 3 CharSetUtils.count("hello", "a-e") = 1 Parameters: str—String to count characters in, may be null set—String set of characters to count, may be null Returns: character count, zero if null string input See Also: for set-syntax. public static int count(java.lang.String str, java.lang.String[] set) Takes an argument in set-syntax, see evaluateSet, and returns the number of characters present in the specified string. An example would be: count("hello", {"c-f", "o"}) returns 2. Parameters: str—String to count characters in, may be null set—String[] set of characters to count, may be null Returns: character count, zero if null string input See Also: for set-syntax. public static java.lang.String keep(java.lang.String str, java.lang.String set) Takes an argument in set-syntax, see evaluateSet, and keeps any of the char- acters present in the specified string. CharSetUtils.keep(null, *) = null CharSetUtils.keep("", *) = "" CharSetUtils.keep(*, null) = "" Iverson_appA.qxd 1/17/05 2:37 PM Page 240 240 Lang Reference Appendix A CharSetUtils.keep(*, "") = "" CharSetUtils.keep("hello", "hl") = "hll" CharSetUtils.keep("hello", "le") = "ell" Parameters: str—String to keep characters from, may be null set—String set of characters to keep, may be null Returns: modified String, null if null string input See Also: for set-syntax. public static java.lang.String keep(java.lang.String str, java.lang.String[] set) Takes an argument in set-syntax, see evaluateSet, and keeps any of the char- acters present in the specified string. An example would be: keep("hello", {"c-f", "o"}) returns "hll" Parameters: str—String to keep characters from, may be null set—String[] set of characters to keep, may be null Returns: modified String, null if null string input See Also: for set-syntax. public static java.lang.String delete(java.lang.String str, java.lang.String set) Takes an argument in set-syntax, see evaluateSet, and deletes any of the char- acters present in the specified string. CharSetUtils.delete(null, *) = null CharSetUtils.delete("", *) = "" CharSetUtils.delete(*, null) = * CharSetUtils.delete(*, "") = * CharSetUtils.delete("hello", "hl") = "hll" CharSetUtils.delete("hello", "le") = "ell" Parameters: str—String to delete characters from, may be null set—String set of characters to delete, may be null Returns: modified String, null if null string input See Also: for set-syntax. public static java.lang.String delete(java.lang.String str, java.lang.String[] set) Takes an argument in set-syntax, see evaluateSet, and deletes any of the char- acters present in the specified string. An example would be: delete("hello", {"c-f", "o"}) returns "hll" Iverson_appA.qxd 1/17/05 2:37 PM Page 241 org.apache.commons.lang.BooleanUtils 241 Parameters: str—String to delete characters from, may be null set—String[] set of characters to delete, may be null Returns: modified String, null if null string input See Also: for set-syntax. org.apache.commons.lang.ClassUtils Operates on classes without using reflection. This class handles invalid null inputs as best it can. Each method docu- ments its behavior in more detail. Field Detail public static final char PACKAGE_SEPARATOR_CHAR The package separator character: .. See Also: Constant Field Values public static final java.lang.String PACKAGE_SEPARATOR The package separator String: . . public static final char INNER_CLASS_SEPARATOR_CHAR The inner class separator character: $. See Also: Constant Field Values public static final java.lang.String INNER_CLASS_SEPARATOR The inner class separator String: $. Constructor Detail public ClassUtils() ClassUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ClassUtils.getShortClassName(cls). This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String getShortClassName(java.lang.Object object, java.lang.String valueIfNull) Gets the class name minus the package name for an Object. Parameters: object—the class to get the short name for, may be null valueIfNull—the value to return if null Iverson_appA.qxd 1/17/05 2:37 PM Page 242 242 Lang Reference Appendix A Returns: the class name of the object without the package name, or the null value public static java.lang.String getShortClassName(java.lang.Class cls) Gets the class name minus the package name from a Class. Parameters: cls—the class to get the short name for, must not be null Returns: the class name without the package name Throws: java.lang.IllegalArgumentException—if the class is null public static java.lang.String getShortClassName(java.lang.String className) Gets the class name minus the package name from a String. The string passed in is assumed to be a class name—it is not checked. Parameters: className—the className to get the short name for, must not be empty or null Returns: the class name of the class without the package name Throws: java.lang.IllegalArgumentException—if the className is empty public static java.lang.String getPackageName(java.lang.Object object, java.lang.String valueIfNull) Gets the package name of an Object. Parameters: object—the class to get the package name for, may be null valueIfNull—the value to return if null Returns: the package name of the object, or the null value public static java.lang.String getPackageName(java.lang.Class cls) Gets the package name of a Class. Parameters: cls—the class to get the package name for, must not be null Returns: the package name Throws: java.lang.IllegalArgumentException—if the class is null public static java.lang.String getPackageName(java.lang.String className) Gets the package name from a String. The string passed in is assumed to be a class name—it is not checked. Parameters: className—the className to get the package name for, must not be empty or null Returns: the package name Throws: java.lang.IllegalArgumentException—if the className is empty Iverson_appA.qxd 1/17/05 2:37 PM Page 243 org.apache.commons.lang.BooleanUtils 243 public static java.util.List getAllSuperclasses(java.lang.Class cls) Gets a List of superclasses for the given class. Parameters: cls—the class to look up, must not be null Returns: the List of superclasses in order going up from this one, null if null input public static java.util.List getAllInterfaces(java.lang.Class cls) Gets a List of all interfaces implemented by the given class and its super- classes. The order is determined by looking through each interface in turn as declared in the source file and following its hieracrchy up. Then each super- class is considered in the same way. Later duplicates are ignored, so the order is maintained. Parameters: cls—the class to look up, must not be null Returns: the List of interfaces in order, null if null input public static java.util.List convertClassNamesToClasses(java.util.List classNames) Given a List of class names, this method converts them into classes. A new List is returned. If the class name cannot be found, null is stored in the List. If the class name in the List is null, null is stored in the output List. Parameters: classNames—the classNames to change Returns: a List of Class objects corresponding to the class names, null if null input Throws: java.lang.ClassCastException—if classNames contains a non String entry public static java.util.List convertClassesToClassNames(java.util.List classes) Given a List of Class objects, this method converts them into class names. A new List is returned. null objects will be copied into the returned list as null. Parameters: classes—the classes to change Returns: a List of Class objects corresponding to the class names, null if null input Throws: java.lang.ClassCastException—if classNames contains a non Class or null entry public static boolean isAssignable(java.lang.Class[] classArray, java.lang.Class[] toClassArray) Iverson_appA.qxd 1/17/05 2:37 PM Page 244 244 Lang Reference Appendix A Checks if an array of Classes can be assigned to another array of Classes. This method calls isAssignable for each Class pair in the input arrays. It can be used to check if a set of arguments (the first parameter) are suitably compatible with a set of method parameter types (the second parameter). Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls. Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases. Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive. Specifically, this method tests whether the type represented by the speci- fied Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details. Parameters: classArray—the array of Classes to check, may be null toClassArray—the array of Classes to try to assign into, may be null Returns: true if assignment possible public static boolean isAssignable(java.lang.Class cls, java.lang.Class toClass) Checks if one Class can be assigned to a variable of another Class. Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls. Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases. Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive. Specifically, this method tests whether the type represented by the speci- fied Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details. Parameters: cls—the Class to check, may be null toClass—the Class to try to assign into, returns false if null Returns: true if assignment possible public static boolean isInnerClass(java.lang.Class cls) Is the specified class an inner class or static nested class. Parameters: cls—the class to check Returns: true if the class is an inner or static nested class, false if not or null Iverson_appA.qxd 1/17/05 2:37 PM Page 245 org.apache.commons.lang.BooleanUtils 245 org.apache.commons.lang.ObjectUtils This class tries to handle null input gracefully. An exception will generally not be thrown for a null input. Each method documents its behavior in more detail. Nested Class Summary static class ObjectUtils.Null Field Detail public static final ObjectUtils.Null NULL Singleton used as a null placeholder where null has another meaning. For example, in a HashMap the HashMap.get(java.lang.Object) method returns null if the Map contains null or if there is no matching key. The Null placeholder can be used to distinguish between these two cases. Another example is Hashtable, where null cannot be stored. This instance is Serializable. Constructor Detail public ObjectUtils() ObjectUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ObjectUtils.defaultIfNull("a","b");. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.Object defaultIfNull(java.lang.Object object, java.lang.Object defaultValue) Returns a default value if the object passed is null. ObjectUtils.defaultIfNull(null, null) = null ObjectUtils.defaultIfNull(null, "") = "" ObjectUtils.defaultIfNull(null, "zz") = "zz" ObjectUtils.defaultIfNull("abc", *) = "abc" ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE Parameters: object—the Object to test, may be null defaultValue—the default value to return, may be null Returns: object if it is not null, defaultValue otherwise public static boolean equals(java.lang.Object object1, java.lang.Object object2) Iverson_appA.qxd 1/17/05 2:37 PM Page 246 246 Lang Reference Appendix A Compares two objects for equality, where either one or both objects may be null. ObjectUtils.equals(null, null) = true ObjectUtils.equals(null, "") = false ObjectUtils.equals("", null) = false ObjectUtils.equals("", "") = true ObjectUtils.equals(Boolean.TRUE, null) = false ObjectUtils.equals(Boolean.TRUE, "true") = false ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false Parameters: object1—the first object, may be null object2—the second object, may be null Returns: true if the values of both objects are the same public static java.lang.String identityToString(java.lang.Object object) Gets the toString that would be produced by Object if a class did not override toString itself. null will return null. ObjectUtils.identityToString(null) = null ObjectUtils.identityToString("") = "java.lang.String@1e23" ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa" Parameters: object—the object to create a toString for, may be null Returns: the default toString text, or null if null passed in public static java.lang.StringBuffer appendIdentityToString(java.lang.StringBuffer buffer, java.lang.Object object) Appends the toString that would be produced by Object if a class did not over- ride toString itself. null will return null. ObjectUtils.appendIdentityToString(*, null) = null ObjectUtils.appendIdentityToString(null, "") = "java.lang.String@1e23" ObjectUtils.appendIdentityToString(null, Boolean.TRUE) = "java.lang.Boolean@7fa" ObjectUtils.appendIdentityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa") Parameters: buffer—the buffer to append to, may be null object—the object to create a toString for, may be null Returns: the default toString text, or null if null passed in public static java.lang.String toString(java.lang.Object obj) Gets the toString of an Object returning an empty string (" ") if null input. Iverson_appA.qxd 1/17/05 2:37 PM Page 247 org.apache.commons.lang.BooleanUtils 247 ObjectUtils.toString(null) = "" ObjectUtils.toString("") = "" ObjectUtils.toString("bat") = "bat" ObjectUtils.toString(Boolean.TRUE) = "true" Parameters: obj—the Object to toString, may be null Returns: the passed in Object’s toString, or nullStr if null input See Also: StringUtils.defaultString(String), String.valueOf(Object) public static java.lang.String toString(java.lang.Object obj, java.lang.String nullStr) Gets the toString of an Object returning a specified text if null input. ObjectUtils.toString(null, null) = null ObjectUtils.toString(null, "null") = "null" ObjectUtils.toString("", "null") = "" ObjectUtils.toString("bat", "null") = "bat" ObjectUtils.toString(Boolean.TRUE, "null") = "true" Parameters: obj—the Object to toString, may be null nullStr—the String to return if null input, may be null Returns: the passed in Object’s toString, or nullStr if null input See Also: StringUtils.defaultString(String,String), String.valueOf(Object) org.apache.commons.lang.ObjectUtils.Null public static class ObjectUtils.Null implements java.io.Serializable Class used as a null placeholder where null has another meaning. For example, in a HashMap the HashMap.get(java.lang.Object) method returns null if the Map contains null or if there is no matching key. The Null placeholder can be used to distinguish between these two cases. Another example is Hashtable, where null cannot be stored. See Also: Serialized Form org.apache.commons.lang.RandomStringUtils Operations for random Strings. Constructor Detail public RandomStringUtils() RandomStringUtils instances should NOT be constructed in standard pro- gramming. Instead, the class should be used as RandomStringUtils.random(5);. Iverson_appA.qxd 1/17/05 2:37 PM Page 248 248 Lang Reference Appendix A This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String random(int count) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of all characters. Parameters: count—the length of random string to create Returns: the random string public static java.lang.String randomAscii(int count) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of characters whose ASCII value is between 32 and 126 (inclusive). Parameters: count—the length of random string to create Returns: the random string public static java.lang.String randomAlphabetic(int count) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of alphabetic characters. Parameters: count—the length of random string to create Returns: the random string public static java.lang.String randomAlphanumeric(int count) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of alpha-numeric characters. Parameters: count—the length of random string to create Returns: the random string public static java.lang.String randomNumeric(int count) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of numeric characters. Parameters: count—the length of random string to create Returns: the random string public static java.lang.String random(int count, boolean letters, boolean numbers) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of alpha-numeric characters as indi- cated by the arguments. Iverson_appA.qxd 1/17/05 2:37 PM Page 249 org.apache.commons.lang.BooleanUtils 249 Parameters: count—the length of random string to create letters—if true, generated string will include alphabetic characters numbers—if true, generatd string will include numeric characters Returns: the random string public static java.lang.String random(int count, int start, int end, boolean letters, boolean numbers) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of alpha-numeric characters as indi- cated by the arguments. Parameters: count—the length of random string to create start—the position in set of chars to start at end—the position in set of chars to end before letters—if true, generated string will include alphabetic characters numbers—if true, generated string will include numeric characters Returns: the random string public static java.lang.String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) Creates a random string based on a variety of options, using default source of randomness. This method has exactly the same semantics as random(int,int,int,boolean,boolean,char[],Random), but instead of using an externally supplied source of randomness, it uses the internal static Random instance. Parameters: count—the length of random string to create start—the position in set of chars to start at end—the position in set of chars to end before letters—only allow letters? numbers—only allow numbers? chars—the set of chars to choose randoms from. If null, then it will use the set of all chars. Returns: the random string Throws: java.lang.ArrayIndexOutOfBoundsException—if there are not (end—start) + 1 characters in the set array. public static java.lang.String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars, java.util.Random random) Creates a random string based on a variety of options, using supplied source of randomness. If start and end are both 0, start and end are set to ' ' and 'z', the ASCII printable characters will be used, unless letters and numbers are both false, in which case, start and end are set to 0 and Integer.MAX_VALUE. If set is not null, characters between start and end are chosen. Iverson_appA.qxd 1/17/05 2:37 PM Page 250 250 Lang Reference Appendix A This method accepts a user-supplied Random instance to use as a source of randomness. By seeding a single Random instance with a fixed seed and using it for each call, the same random sequence of strings can be generated repeatedly and predictably. Parameters: count—the length of random string to create start—the position in set of chars to start at end—the position in set of chars to end before letters—only allow letters? numbers—only allow numbers? chars—the set of chars to choose randoms from. If null, then it will use the set of all chars. random—a source of randomness Returns: the random string Throws: java.lang.ArrayIndexOutOfBoundsException—if there are not (end—start) + 1 characters in the set array. java.lang.IllegalArgumentException—if count < 0. public static java.lang.String random(int count, java.lang.String chars) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of characters specified. Parameters: count—the length of random string to create chars—the String containing the set of characters to use, may be null Returns: the random string Throws: java.lang.IllegalArgumentException—if count < 0. public static java.lang.String random(int count, char[] chars) Creates a random string whose length is the number of characters specified. Characters will be chosen from the set of characters specified. Parameters: count—the length of random string to create chars—the character array containing the set of characters to use, may be null Returns: the random string Throws: java.lang.IllegalArgumentException—if count < 0. org.apache.commons.lang.SerializationUtils Assists with the serialization process and performs additional functionality based on serialization. ☞ Deep clone using serialization ☞ Serialize managing finally and IOException ☞ Deserialize managing finally and IOException Iverson_appA.qxd 1/17/05 2:37 PM Page 251 org.apache.commons.lang.BooleanUtils 251 This class throws exceptions for invalid null inputs. Each method documents its behavior in more detail. Constructor Detail public SerializationUtils() SerializationUtils instances should NOT be constructed in standard program- ming. Instead, the class should be used as SerializationUtils.clone(object). This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.Object clone(java.io.Serializable object) Deep clone an Object using serialization. This is many times slower than writ- ing clone methods by hand on all objects in your object graph. However, for complex object graphs, or for those that don’t support deep cloning, this can be a simple alternative implementation. Of course all the objects must be Serializable. Parameters: object—the Serializable object to clone Returns: the cloned object Throws: SerializationException—(runtime) if the serialization fails public static void serialize(java.io.Serializable obj, java.io.OutputStream outputStream) Serializes an Object to the specified stream. The stream will be closed once the object is written. This avoids the need for a finally clause, and maybe also exception handling, in the application code. The stream passed in is not buffered internally within this method. This is the responsibility of your application if desired. Parameters: obj—the object to serialize to bytes, may be null outputStream—the stream to write to, must not be null Throws: java.lang.IllegalArgumentException—if outputStream is null SerializationException—(runtime) if the serialization fails public static byte[] serialize(java.io.Serializable obj) Serializes an Object to a byte array for storage/serialization. Parameters: obj—the object to serialize to bytes Returns: a byte[] with the converted Serializable Throws: SerializationException—(runtime) if the serialization fails public static java.lang.Object deserialize(java.io.InputStream inputStream) Iverson_appA.qxd 1/17/05 2:37 PM Page 252 252 Lang Reference Appendix A Deserializes an Object from the specified stream. The stream will be closed once the object is written. This avoids the need for a finally clause, and maybe also exception handling, in the application code. The stream passed in is not buffered internally within this method. This is the responsibility of your application if desired. Parameters: inputStream—the serialized object input stream, must not be null Returns: the deserialized object Throws: java.lang.IllegalArgumentException—if inputStream is null SerializationException—(runtime) if the serialization fails public static java.lang.Object deserialize(byte[] objectData) Deserializes a single Object from an array of bytes. Parameters: objectData—the serialized object, must not be null Returns: the deserialized object Throws: java.lang.IllegalArgumentException—if objectData is null SerializationException—(runtime) if the serialization fails org.apache.commons.lang.StringEscapeUtils Escapes and unescapes Strings for Java, Java Script, HTML, XML, and SQL. Constructor Detail public StringEscapeUtils() StringEscapeUtils instances should NOT be constructed in standard program- ming. Instead, the class should be used as: StringEscapeUtils.escapeJava("foo"); This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String escapeJava(java.lang.String str) Escapes the characters in a String using Java String rules. Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.). So a tab becomes the characters '\\' and 't'. The only difference between Java strings and JavaScript strings is that in JavaScript, a single quote must be escaped. Example: input string: He didn't say, "Stop!" output string: He didn't say, \"Stop!\" Iverson_appA.qxd 1/17/05 2:37 PM Page 253 org.apache.commons.lang.BooleanUtils 253 Parameters: str—String to escape values in, may be null Returns: String with escaped values, null if null string input public static void escapeJava(java.io.Writer out, java.lang.String str) throws java.io.IOException Escapes the characters in a String using Java String rules to a Writer. A null string input has no effect. Parameters: out—Writer to write escaped string into str—String to escape values in, may be null Throws: java.lang.IllegalArgumentException—if the Writer is null java.io.IOException—if error occurs on underlying Writer See Also: escapeJava(java.lang.String) public static java.lang.String escapeJavaScript(java.lang.String str) Escapes the characters in a String using JavaScript String rules. Escapes any values it finds into their JavaScript String form. Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.). So a tab becomes the characters '\\' and 't'. The only difference between Java strings and JavaScript strings is that in JavaScript, a single quote must be escaped. Example: input string: He didn't say, "Stop!" output string: He didn\'t say, \"Stop!\" Parameters: str—String to escape values in, may be null Returns: String with escaped values, null if null string input public static void escapeJavaScript(java.io.Writer out, java.lang.String str) throws java.io.IOException Escapes the characters in a String using JavaScript String rules to a Writer. A null string input has no effect. Parameters: out—Writer to write escaped string into str—String to escape values in, may be null Throws: java.lang.IllegalArgumentException—if the Writer is null java.io.IOException—if error occurs on underlying Writer See Also: escapeJavaScript(java.lang.String) public static java.lang.String unescapeJava(java.lang.String str) Unescapes any Java literals found in the String. For example, it will turn a sequence of '\' and 'n' into a newline character, unless the '\' is preceded by another '\'. Iverson_appA.qxd 1/17/05 2:37 PM Page 254 254 Lang Reference Appendix A Parameters: str—the String to unescape, may be null Returns: a new unescaped String, null if null string input public static void unescapeJava(java.io.Writer out, java.lang.String str) throws java.io.IOException Unescapes any Java literals found in the String to a Writer. For example, it will turn a sequence of '\' and 'n' into a newline character, unless the '\' is pre- ceded by another '\'. A null string input has no effect. Parameters: out—the Writer used to output unescaped characters str—the String to unescape, may be null Throws: java.lang.IllegalArgumentException—if the Writer is null java.io.IOException—if error occurs on underlying Writer public static java.lang.String unescapeJavaScript(java.lang.String str) Unescapes any JavaScript literals found in the String. For example, it will turn a sequence of '\' and 'n' into a newline character, unless the '\' is pre- ceded by another '\'. Parameters: str—the String to unescape, may be null Returns: A new unescaped String, null if null string input See Also: unescapeJava(String) public static void unescapeJavaScript(java.io.Writer out, java.lang.String str) throws java.io.IOException Unescapes any JavaScript literals found in the String to a Writer. For example, it will turn a sequence of '\' and 'n' into a newline character, unless the '\' is preceded by another '\'. A null string input has no effect. Parameters: out—the Writer used to output unescaped characters str—the String to unescape, may be null Throws: java.lang.IllegalArgumentException—if the Writer is null java.io.IOException—if error occurs on underlying Writer See Also: unescapeJava(Writer,String) public static java.lang.String escapeHtml(java.lang.String str) Escapes the characters in a String using HTML entities. For example: "butter". "bread" & "butter" => "bread" & Supports all known HTML 4.0 entities, including funky accents. Parameters: str—the String to escape, may be null Returns: a new escaped String, null if null string input Iverson_appA.qxd 1/17/05 2:37 PM Page 255 org.apache.commons.lang.BooleanUtils 255 See Also: unescapeHtml(String), ISO Entities, HTML 3.2 Character Entities for ISO Latin-1, HTML 4.0 Character entity references, HTML 4.01 Character References, HTML 4.01 Code positions public static java.lang.String unescapeHtml(java.lang.String str) Unescapes a string containing entity escapes to a string containing the actual Unicode characters corresponding to the escapes. Supports HTML 4.0 entities. "<Français>" will become For example, the string "" If an entity is unrecognized, it is left alone, and inserted verbatim into the result string. e.g. ">&zzzz;x" will become ">&zzzz;x". Parameters: str—the String to unescape, may be null Returns: a new unescaped String, null if null string input See Also: escapeHtml(String) public static java.lang.String escapeXml(java.lang.String str) Escapes the characters in a String using XML entities. For example: "butter". "bread" & "butter" => "bread" & Supports only the four basic XML entities (gt, lt, quot, amp). Does not support DTDs or external entities. Parameters: str—the String to escape, may be null Returns: a new escaped String, null if null string input See Also: unescapeXml(java.lang.String) public static java.lang.String unescapeXml(java.lang.String str) Unescapes a string containing XML entity escapes to a string containing the actual Unicode characters corresponding to the escapes. Supports only the four basic XML entities (gt, lt, quot, amp). Does not support DTDs or external entities. Parameters: str—the String to unescape, may be null Returns: a new unescaped String, null if null string input See Also: escapeXml(String) public static java.lang.String escapeSql(java.lang.String str) Escapes the characters in a String to be suitable to pass to an SQL query. For example, statement.executeQuery("SELECT * FROM MOVIES WHERE TITLE='" + StringEscapeUtils.escapeSql("McHale's Navy") + "'"); Iverson_appA.qxd 1/17/05 2:37 PM Page 256 256 Lang Reference Appendix A At present, this method only turns single-quotes into doubled single-quotes ("McHale’s Navy" => "McHale’s Navy"). It does not handle the cases of percent (%) or underscore (_) for use in LIKE clauses. see http://www.jguru.com/faq/view.jsp?EID=8881 Parameters: str—the string to escape, may be null Returns: a new String, escaped for SQL, null if null string input org.apache.commons.lang.StringUtils Operations on String that are null safe. ☞ IsEmpty/IsBlank—checks if a String contains text ☞ Trim/Strip—removes leading and trailing whitespace ☞ Equals—compares two strings null-safe ☞ IndexOf/LastIndexOf/Contains—null-safe index-of checks ☞ IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut—index-of any of a set of Strings ☞ ContainsOnly/ContainsNone—does String contains only/none of these char- acters ☞ Substring/Left/Right/Mid—null-safe substring extractions ☞ SubstringBefore/SubstringAfter/SubstringBetween—substring extraction relative to other strings ☞ Split/Join—splits a String into an array of substrings and vice versa ☞ Replace/Delete/Overlay—Searches a String and replaces one String with another ☞ Chomp/Chop—removes the last part of a String ☞ LeftPad/RightPad/Center/Repeat—pads a String ☞ UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize—changes the case of a String ☞ CountMatches—counts the number of occurrences of one String in another ☞ IsAlpha/IsNumeric/IsWhitespace—checks the characters in a String ☞ DefaultString—protects against a null input String ☞ Reverse/ReverseDelimited—reverses a String ☞ Abbreviate—abbreviates a String using ellipsis ☞ Difference—compares two strings and reports on their differences ☞ LevensteinDistance—the number of changes needed to change one String into another The StringUtils class defines certain words related to String handling. ☞ null—null ☞ empty—a zero-length string ("") Iverson_appA.qxd 1/17/05 2:37 PM Page 257 org.apache.commons.lang.BooleanUtils 257 ☞ space—the space character (' ', char 32) ☞ whitespace—the characters defined by Character.isWhitespace(char) ☞ trim—the characters <= 32 as in String.trim() StringUtils handles null input Strings quietly. That is to say that a null input will return null. Where a boolean or int is being returned, details vary by method. A side effect of the null handling is that a NullPointerException should be considered a bug in StringUtils (except for deprecated methods). Methods in this class give sample code to explain their operation. The symbol * is used to indicate any input including null. Field Detail public static final java.lang.String EMPTY The empty String "". See Also: Constant Field Values Constructor Detail public StringUtils() StringUtils instances should NOT be constructed in standard programming. Instead, the class should be used as StringUtils.trim("foo");. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static boolean isEmpty(java.lang.String str) Checks if a String is empty (" ") or null. StringUtils.isEmpty(null) = true StringUtils.isEmpty("") = true StringUtils.isEmpty(" ") = false StringUtils.isEmpty("bob") = false StringUtils.isEmpty(" bob ") = false NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank(). Parameters: str—the String to check, may be null Returns: true if the String is empty or null public static boolean isNotEmpty(java.lang.String str) Iverson_appA.qxd 1/17/05 2:37 PM Page 258 258 Lang Reference Appendix A Checks if a String is not empty (" ") and not null. StringUtils.isNotEmpty(null) = false StringUtils.isNotEmpty("") = false StringUtils.isNotEmpty(" ") = true StringUtils.isNotEmpty("bob") = true StringUtils.isNotEmpty(" bob ") = true Parameters: str—the String to check, may be null Returns: true if the String is not empty and not null public static boolean isBlank(java.lang.String str) Checks if a String is whitespace, empty (" ") or null. StringUtils.isBlank(null) = true StringUtils.isBlank("") = true StringUtils.isBlank(" ") = true StringUtils.isBlank("bob") = false StringUtils.isBlank(" bob ") = false Parameters: str—the String to check, may be null Returns: true if the String is null, empty or whitespace public static boolean isNotBlank(java.lang.String str) Checks if a String is not empty (" "), not null and not whitespace only. StringUtils.isNotBlank(null) = false StringUtils.isNotBlank("") = false StringUtils.isNotBlank(" ") = false StringUtils.isNotBlank("bob") = true StringUtils.isNotBlank(" bob ") = true Parameters: str—the String to check, may be null Returns: true if the String is not empty and not null and not whitespace public static java.lang.String trim(java.lang.String str) Removes control characters (char <= 32) from both ends of this String, han- dling null by returning null. The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use strip(String). To trim your choice of characters, use the strip(String, String) methods. StringUtils.trim(null) = null StringUtils.trim("") = "" StringUtils.trim(" ") = "" StringUtils.trim("abc") = "abc" StringUtils.trim(" abc ") = "abc" Iverson_appA.qxd 1/17/05 2:37 PM Page 259 org.apache.commons.lang.BooleanUtils 259 Parameters: str—the String to be trimmed, may be null Returns: the trimmed string, null if null String input public static java.lang.String trimToNull(java.lang.String str) Removes control characters (char <= 32) from both ends of this String return- ing null if the String is empty (" ") after the trim or if it is null. The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToNull(String). StringUtils.trimToNull(null) = null StringUtils.trimToNull("") = null StringUtils.trimToNull(" ") = null StringUtils.trimToNull("abc") = "abc" StringUtils.trimToNull(" abc ") = "abc" Parameters: str—the String to be trimmed, may be null Returns: the trimmed String, null if only chars <= 32, empty or null String input public static java.lang.String trimToEmpty(java.lang.String str) Removes control characters (char <= 32) from both ends of this String return- ing an empty String (" ") if the String is empty (" ") after the trim or if it is null. The String is trimmed using String.trim(). Trim removes start and end characters <= 32. To strip whitespace use stripToEmpty(String). StringUtils.trimToEmpty(null) = "" StringUtils.trimToEmpty("") = "" StringUtils.trimToEmpty(" ") = "" StringUtils.trimToEmpty("abc") = "abc" StringUtils.trimToEmpty(" abc ") = "abc" Parameters: str—the String to be trimmed, may be null Returns: the trimmed String, or an empty String if null input public static java.lang.String strip(java.lang.String str) Strips whitespace from the start and end of a String. This is similar to trim(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char). A null input String returns null. StringUtils.strip(null) = null StringUtils.strip("") = "" StringUtils.strip(" ") = "" StringUtils.strip("abc") = "abc" Iverson_appA.qxd 1/17/05 2:37 PM Page 260 260 Lang Reference Appendix A StringUtils.strip(" abc") = "abc" StringUtils.strip("abc ") = "abc" StringUtils.strip(" abc ") = "abc" StringUtils.strip(" ab c ") = "ab c" Parameters: str—the String to remove whitespace from, may be null Returns: the stripped String, null if null String input public static java.lang.String stripToNull(java.lang.String str) Strips whitespace from the start and end of a String returning null if the String is empty (" ") after the strip. This is similar to trimToNull(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char). StringUtils.strip(null) = null StringUtils.strip("") = null StringUtils.strip(" ") = null StringUtils.strip("abc") = "abc" StringUtils.strip(" abc") = "abc" StringUtils.strip("abc ") = "abc" StringUtils.strip(" abc ") = "abc" StringUtils.strip(" ab c ") = "ab c" Parameters: str—the String to be stripped, may be null Returns: the stripped String, null if whitespace, empty or null String input public static java.lang.String stripToEmpty(java.lang.String str) Strips whitespace from the start and end of a String returning an empty String if null input. This is similar to trimToEmpty(String) but removes whitespace. Whitespace is defined by Character.isWhitespace(char). StringUtils.strip(null) = "" StringUtils.strip("") = "" StringUtils.strip(" ") = "" StringUtils.strip("abc") = "abc" StringUtils.strip(" abc") = "abc" StringUtils.strip("abc ") = "abc" StringUtils.strip(" abc ") = "abc" StringUtils.strip(" ab c ") = "ab c" Parameters: str—the String to be stripped, may be null Returns: the trimmed String, or an empty String if null input public static java.lang.String strip(java.lang.String str, java.lang.String stripChars) Iverson_appA.qxd 1/17/05 2:37 PM Page 261 org.apache.commons.lang.BooleanUtils 261 Strips any of a set of characters from the start and end of a String. This is sim- ilar to String.trim() but allows the characters to be stripped to be controlled. A null input String returns null. An empty string ("") input returns the empty string. If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char). Alternatively use strip(String). StringUtils.strip(null, *) = null StringUtils.strip("", *) = "" StringUtils.strip("abc", null) = "abc" StringUtils.strip(" abc", null) = "abc" StringUtils.strip("abc ", null) = "abc" StringUtils.strip(" abc ", null) = "abc" StringUtils.strip(" abcyx", "xyz") = " abc" Parameters: str—the String to remove characters from, may be null stripChars—the characters to remove, null treated as whitespace Returns: the stripped String, null if null String input public static java.lang.String stripStart(java.lang.String str, java.lang.String stripChars) Strips any of a set of characters from the start of a String. A null input String returns null. An empty string (" ") input returns the empty string. If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char). StringUtils.stripStart(null, *) = null StringUtils.stripStart("", *) = "" StringUtils.stripStart("abc", "") = "abc" StringUtils.stripStart("abc", null) = "abc" StringUtils.stripStart(" abc", null) = "abc" StringUtils.stripStart("abc ", null) = "abc " StringUtils.stripStart(" abc ", null) = "abc " StringUtils.stripStart("yxabc ", "xyz") = "abc " Parameters: str—the String to remove characters from, may be null stripChars—the characters to remove, null treated as whitespace Returns: the stripped String, null if null String input public static java.lang.String stripEnd(java.lang.String str, java.lang.String stripChars) Strips any of a set of characters from the end of a String. A null input String returns null. An empty string (" ") input returns the empty string. If the stripChars String is null, whitespace is stripped as defined by Character.isWhitespace(char). StringUtils.stripEnd(null, *) = null StringUtils.stripEnd("", *) = "" StringUtils.stripEnd("abc", "") = "abc" Iverson_appA.qxd 1/17/05 2:37 PM Page 262 262 Lang Reference Appendix A StringUtils.stripEnd("abc", null) = "abc" StringUtils.stripEnd(" abc", null) = " abc" StringUtils.stripEnd("abc ", null) = "abc" StringUtils.stripEnd(" abc ", null) = " abc" StringUtils.stripEnd(" abcyx", "xyz") = " abc" Parameters: str—the String to remove characters from, may be null stripChars—the characters to remove, null treated as whitespace Returns: the stripped String, null if null String input public static java.lang.String[] stripAll(java.lang.String[] strs) Strips whitespace from the start and end of every String in an array. Whitespace is defined by Character.isWhitespace(char). A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored. StringUtils.stripAll(null) = null StringUtils.stripAll([]) = [] StringUtils.stripAll(["abc", " abc"]) = ["abc", "abc"] StringUtils.stripAll(["abc ", null]) = ["abc", null] Parameters: strs—the array to remove whitespace from, may be null Returns: the stripped Strings, null if null array input public static java.lang.String[] stripAll(java.lang.String[] strs, java.lang.String stripChars) Strips any of a set of characters from the start and end of every String in an array. Whitespace is defined by Character.isWhitespace(char). A new array is returned each time, except for length zero. A null array will return null. An empty array will return itself. A null array entry will be ignored. A null stripChars will strip whitespace as defined by Character.isWhitespace(char). StringUtils.stripAll(null, *) = null StringUtils.stripAll([], *) = [] StringUtils.stripAll(["abc", " abc"], null) = ["abc", "abc"] StringUtils.stripAll(["abc ", null], null) = ["abc", null] StringUtils.stripAll(["abc ", null], "yz") = ["abc ", null] StringUtils.stripAll(["yabcz", null], "yz") = ["abc", null] Parameters: strs—the array to remove characters from, may be null stripChars—the characters to remove, null treated as whitespace Returns: the stripped Strings, null if null array input public static boolean equals(java.lang.String str1, java.lang.String str2) Iverson_appA.qxd 1/17/05 2:37 PM Page 263 org.apache.commons.lang.BooleanUtils 263 Compares two Strings, returning true if they are equal. nulls are handled without exceptions. Two null references are considered to be equal. The com- parison is case sensitive. StringUtils.equals(null, null) = true StringUtils.equals(null, "abc") = false StringUtils.equals("abc", null) = false StringUtils.equals("abc", "abc") = true StringUtils.equals("abc", "ABC") = false Parameters: str1—the first String, may be null str2—the second String, may be null Returns: true if the Strings are equal, case sensitive, or both null See Also: String.equals(Object) public static boolean equalsIgnoreCase(java.lang.String str1, java.lang.String str2) Compares two Strings, returning true if they are equal ignoring the case. nulls are handled without exceptions. Two null references are considered equal. Comparison is case insensitive. StringUtils.equalsIgnoreCase(null, null) = true StringUtils.equalsIgnoreCase(null, "abc") = false StringUtils.equalsIgnoreCase("abc", null) = false StringUtils.equalsIgnoreCase("abc", "abc") = true StringUtils.equalsIgnoreCase("abc", "ABC") = true Parameters: str1—the first String, may be null str2—the second String, may be null Returns: true if the Strings are equal, case insensitive, or both null See Also: String.equalsIgnoreCase(String) public static int indexOf(java.lang.String str, char searchChar) Finds the first index within a String, handling null. This method uses String.indexOf(int). A null or empty (" ") String will return -1. StringUtils.indexOf(null, *) = -1 StringUtils.indexOf("", *) = -1 StringUtils.indexOf("aabaabaa", 'a') = 0 StringUtils.indexOf("aabaabaa", 'b') = 2 Parameters: str—the String to check, may be null searchChar—the character to find Returns: the first index of the search character, -1 if no match or null string input public static int indexOf(java.lang.String str, char searchChar, int startPos) Iverson_appA.qxd 1/17/05 2:37 PM Page 264 264 Lang Reference Appendix A Finds the first index within a String from a start position, handling null. This method uses String.indexOf(int, int). A null or empty (" ") String will return -1. A negative start position is treated as zero. A start position greater than the string length returns -1. StringUtils.indexOf(null, *, *) = -1 StringUtils.indexOf("", *, *) = -1 StringUtils.indexOf("aabaabaa", 'b', 0) = 2 StringUtils.indexOf("aabaabaa", 'b', 3) = 5 StringUtils.indexOf("aabaabaa", 'b', 9) = -1 StringUtils.indexOf("aabaabaa", 'b', -1) = 2 Parameters: str—the String to check, may be null searchChar—the character to find startPos—the start position, negative treated as zero Returns: the first index of the search character, -1 if no match or null string input public static int indexOf(java.lang.String str, java.lang.String searchStr) Finds the first index within a String, handling null. This method uses String.indexOf(String). A null String will return -1. StringUtils.indexOf(null, *) = -1 StringUtils.indexOf(*, null) = -1 StringUtils.indexOf("", "") = 0 StringUtils.indexOf("aabaabaa", "a") = 0 StringUtils.indexOf("aabaabaa", "b") = 2 StringUtils.indexOf("aabaabaa", "ab") = 1 StringUtils.indexOf("aabaabaa", "") = 0 Parameters: str—the String to check, may be null searchStr—the String to find, may be null Returns: the first index of the search String, -1 if no match or null string input public static int indexOf(java.lang.String str, java.lang.String searchStr, int startPos) Finds the first index within a String, handling null. This method uses String.indexOf(String, int). A null String will return -1. A negative start position is treated as zero. An empty (" ") search String always matches. A start position greater than the string length only matches an empty search String. StringUtils.indexOf(null, *, *) = -1 StringUtils.indexOf(*, null, *) = -1 StringUtils.indexOf("", "", 0) = 0 StringUtils.indexOf("aabaabaa", "a", 0) = 0 Iverson_appA.qxd 1/17/05 2:37 PM Page 265 org.apache.commons.lang.BooleanUtils 265 StringUtils.indexOf("aabaabaa", "b", 0) = 2 StringUtils.indexOf("aabaabaa", "ab", 0) = 1 StringUtils.indexOf("aabaabaa", "b", 3) = 5 StringUtils.indexOf("aabaabaa", "b", 9) = -1 StringUtils.indexOf("aabaabaa", "b", -1) = 2 StringUtils.indexOf("aabaabaa", "", 2) = 2 StringUtils.indexOf("abc", "", 9) = 3 Parameters: str—the String to check, may be null searchStr—the String to find, may be null startPos—the start position, negative treated as zero Returns: the first index of the search String, -1 if no match or null string input public static int lastIndexOf(java.lang.String str, char searchChar) Finds the last index within a String, handling null. This method uses String.lastIndexOf(int). A null or empty (" ") String will return -1. StringUtils.lastIndexOf(null, *) = -1 StringUtils.lastIndexOf("", *) = -1 StringUtils.lastIndexOf("aabaabaa", 'a') = 7 StringUtils.lastIndexOf("aabaabaa", 'b') = 5 Parameters: str—the String to check, may be null searchChar—the character to find Returns: the last index of the search character, -1 if no match or null string input public static int lastIndexOf(java.lang.String str, char searchChar, int startPos) Finds the last index within a String from a start position, handling null. This method uses String.lastIndexOf(int, int). A null or empty (" ") String will return -1. A negative start position returns -1. A start position greater than the string length searches the whole string. StringUtils.lastIndexOf(null, *, *) = -1 StringUtils.lastIndexOf("", *, *) = -1 StringUtils.lastIndexOf("aabaabaa", 'b', 8) = 5 StringUtils.lastIndexOf("aabaabaa", 'b', 4) = 2 StringUtils.lastIndexOf("aabaabaa", 'b', 0) = -1 StringUtils.lastIndexOf("aabaabaa", 'b', 9) = 5 StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1 StringUtils.lastIndexOf("aabaabaa", 'a', 0) = 0 Parameters: str—the String to check, may be null searchChar—the character to find startPos—the start position Iverson_appA.qxd 1/17/05 2:37 PM Page 266 266 Lang Reference Appendix A Returns: the last index of the search character, -1 if no match or null string input public static int lastIndexOf(java.lang.String str, java.lang.String searchStr) Finds the last index within a String, handling null. This method uses String.lastIndexOf(String). A null String will return -1. StringUtils.lastIndexOf(null, *) = -1 StringUtils.lastIndexOf(*, null) = -1 StringUtils.lastIndexOf("", "") = 0 StringUtils.lastIndexOf("aabaabaa", "a") = 0 StringUtils.lastIndexOf("aabaabaa", "b") = 2 StringUtils.lastIndexOf("aabaabaa", "ab") = 1 StringUtils.lastIndexOf("aabaabaa", "") = 8 Parameters: str—the String to check, may be null searchStr—the String to find, may be null Returns: the last index of the search String, -1 if no match or null string input public static int lastIndexOf(java.lang.String str, java.lang.String searchStr, int startPos) Finds the first index within a String, handling null. This method uses String.lastIndexOf(String, int). A null String will return -1. A negative start position returns -1. An empty (" ") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string. StringUtils.lastIndexOf(null, *, *) = -1 StringUtils.lastIndexOf(*, null, *) = -1 StringUtils.lastIndexOf("aabaabaa", "a", 8) = 7 StringUtils.lastIndexOf("aabaabaa", "b", 8) = 5 StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4 StringUtils.lastIndexOf("aabaabaa", "b", 9) = 5 StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1 StringUtils.lastIndexOf("aabaabaa", "a", 0) = 0 StringUtils.lastIndexOf("aabaabaa", "b", 0) = -1 Parameters: str—the String to check, may be null searchStr—the String to find, may be null startPos—the start position, negative treated as zero Returns: the first index of the search String, -1 if no match or null string input public static boolean contains(java.lang.String str, char searchChar) Iverson_appA.qxd 1/17/05 2:37 PM Page 267 org.apache.commons.lang.BooleanUtils 267 Checks if String contains a search character, handling null. This method uses String.indexOf(int). A null or empty (" ") String will return false. StringUtils.contains(null, *) = false StringUtils.contains("", *) = false StringUtils.contains("abc", 'a') = true StringUtils.contains("abc", 'z') = false Parameters: str—the String to check, may be null searchChar—the character to find Returns: true if the String contains the search character, false if not or null string input public static boolean contains(java.lang.String str, java.lang.String searchStr) Find the first index within a String, handling null. This method uses String.indexOf(int). A null String will return false. StringUtils.contains(null, *) = false StringUtils.contains(*, null) = false StringUtils.contains("", "") = true StringUtils.contains("abc", "") = true StringUtils.contains("abc", "a") = true StringUtils.contains("abc", "z") = false Parameters: str—the String to check, may be null searchStr—the String to find, may be null Returns: true if the String contains the search character, false if not or null string input public static int indexOfAny(java.lang.String str, char[] searchChars) Search a String to find the first index of any character in the given set of characters. A null String will return -1. A null or zero length search array will return -1. StringUtils.indexOfAny(null, *) = -1 StringUtils.indexOfAny("", *) = -1 StringUtils.indexOfAny(*, null) = -1 StringUtils.indexOfAny(*, []) = -1 StringUtils.indexOfAny("zzabyycdxx",['z','a']) = 0 StringUtils.indexOfAny("zzabyycdxx",['b','y']) = 3 StringUtils.indexOfAny("aba", ['z']) = -1 Parameters: str—the String to check, may be null searchChars—the chars to search for, may be null Iverson_appA.qxd 1/17/05 2:37 PM Page 268 268 Lang Reference Appendix A Returns: the index of any of the chars, -1 if no match or null input public static int indexOfAny(java.lang.String str, java.lang.String searchChars) Search a String to find the first index of any character in the given set of characters. A null String will return -1. A null search string will return -1. StringUtils.indexOfAny(null, *) = -1 StringUtils.indexOfAny("", *) = -1 StringUtils.indexOfAny(*, null) = -1 StringUtils.indexOfAny(*, "") = -1 StringUtils.indexOfAny("zzabyycdxx", "za") = 0 StringUtils.indexOfAny("zzabyycdxx", "by") = 3 StringUtils.indexOfAny("aba","z") = -1 Parameters: str—the String to check, may be null searchChars—the chars to search for, may be null Returns: the index of any of the chars, -1 if no match or null input public static int indexOfAnyBut(java.lang.String str, char[] searchChars) Search a String to find the first index of any character not in the given set of characters. A null String will return -1. A null or zero length search array will return -1. StringUtils.indexOfAnyBut(null, *) = -1 StringUtils.indexOfAnyBut("", *) = -1 StringUtils.indexOfAnyBut(*, null) = -1 StringUtils.indexOfAnyBut(*, []) = -1 StringUtils.indexOfAnyBut("zzabyycdxx",'za') = 3 StringUtils.indexOfAnyBut("zzabyycdxx", '') = 0 StringUtils.indexOfAnyBut("aba", 'ab') = -1 Parameters: str—the String to check, may be null searchChars—the chars to search for, may be null Returns: the index of any of the chars, -1 if no match or null input public static int indexOfAnyBut(java.lang.String str, java.lang.String searchChars) Search a String to find the first index of any character not in the given set of characters. A null String will return -1. A null search string will return -1. StringUtils.indexOfAnyBut(null, *) = -1 StringUtils.indexOfAnyBut("", *) = -1 StringUtils.indexOfAnyBut(*, null) = -1 Iverson_appA.qxd 1/17/05 2:37 PM Page 269 org.apache.commons.lang.BooleanUtils 269 StringUtils.indexOfAnyBut(*, "") = -1 StringUtils.indexOfAnyBut("zzabyycdxx", "za") = 3 StringUtils.indexOfAnyBut("zzabyycdxx", "") = 0 StringUtils.indexOfAnyBut("aba","ab") = -1 Parameters: str—the String to check, may be null searchChars—the chars to search for, may be null Returns: the index of any of the chars, -1 if no match or null input public static boolean containsOnly(java.lang.String str, char[] valid) Checks if the String contains only certain characters. A null String will return false. A null valid character array will return false. An empty String (" ") always returns true. StringUtils.containsOnly(null, *) = false StringUtils.containsOnly(*, null) = false StringUtils.containsOnly("", *) = true StringUtils.containsOnly("ab", '') = false StringUtils.containsOnly("abab", 'abc') = true StringUtils.containsOnly("ab1", 'abc') = false StringUtils.containsOnly("abz", 'abc') = false Parameters: str—the String to check, may be null valid—an array of valid chars, may be null Returns: true if it only contains valid chars and is non-null public static boolean containsOnly(java.lang.String str, java.lang.String validChars) Checks if the String contains only certain characters. A null String will return false. A null valid character String will return false. An empty String (" ") always returns true. StringUtils.containsOnly(null, *) = false StringUtils.containsOnly(*, null) = false StringUtils.containsOnly("", *) = true StringUtils.containsOnly("ab", "") = false StringUtils.containsOnly("abab", "abc") = true StringUtils.containsOnly("ab1", "abc") = false StringUtils.containsOnly("abz", "abc") = false Parameters: str—the String to check, may be null validChars—a String of valid chars, may be null Returns: true if it only contains valid chars and is non-null public static boolean containsNone(java.lang.String str, char[] invalidChars) Checks that the String does not contain certain characters. Iverson_appA.qxd 1/17/05 2:37 PM Page 270 270 Lang Reference Appendix A A null String will return true. A null invalid character array will return true. An empty String (" ") always returns true. StringUtils.containsNone(null, *) = true StringUtils.containsNone(*, null) = true StringUtils.containsNone("", *) = true StringUtils.containsNone("ab", '') = true StringUtils.containsNone("abab", 'xyz') = true StringUtils.containsNone("ab1", 'xyz') = true StringUtils.containsNone("abz", 'xyz') = false Parameters: str—the String to check, may be null invalidChars—an array of invalid chars, may be null Returns: true if it contains none of the invalid chars, or is null public static boolean containsNone(java.lang.String str, java.lang.String invalidChars) Checks that the String does not contain certain characters. A null String will return true. A null invalid character array will return true. An empty String (" ") always returns true. StringUtils.containsNone(null, *) = true StringUtils.containsNone(*, null) = true StringUtils.containsNone("", *) = true StringUtils.containsNone("ab", "") = true StringUtils.containsNone("abab", "xyz") = true StringUtils.containsNone("ab1", "xyz") = true StringUtils.containsNone("abz", "xyz") = false Parameters: str—the String to check, may be null invalidChars—a String of invalid chars, may be null Returns: true if it contains none of the invalid chars, or is null public static int indexOfAny(java.lang.String str, java.lang.String[] searchStrs) Find the first index of any of a set of potential substrings. A null String will return -1. A null or zero length search array will return -1. A null search array entry will be ignored, but a search array containing " " will return 0 if str is not null. This method uses String.indexOf(String). StringUtils.indexOfAny(null, *) = -1 StringUtils.indexOfAny(*, null) = -1 StringUtils.indexOfAny(*, []) = -1 StringUtils.indexOfAny("zzabyycdxx", ["ab","cd"]) = 2 StringUtils.indexOfAny("zzabyycdxx", ["cd","ab"]) = 2 StringUtils.indexOfAny("zzabyycdxx", ["mn","op"]) = -1 StringUtils.indexOfAny("zzabyycdxx", ["zab","aby"]) = 1 StringUtils.indexOfAny("zzabyycdxx", [""]) = 0 StringUtils.indexOfAny("", [""]) = 0 StringUtils.indexOfAny("", ["a"]) = -1 Iverson_appA.qxd 1/17/05 2:37 PM Page 271 org.apache.commons.lang.BooleanUtils 271 Parameters: str—the String to check, may be null searchStrs—the Strings to search for, may be null Returns: the first index of any of the searchStrs in str, -1 if no match public static int lastIndexOfAny(java.lang.String str, java.lang.String[] searchStrs) Find the latest index of any of a set of potential substrings. A null String will return -1. A null search array will return -1. A null or zero length search array entry will be ignored, but a search array containing " " will return the length of str if str is not null. This method uses String.indexOf(String). StringUtils.lastIndexOfAny(null, *) = -1 StringUtils.lastIndexOfAny(*, null) = -1 StringUtils.lastIndexOfAny(*, []) = -1 StringUtils.lastIndexOfAny(*, [null]) = -1 StringUtils.lastIndexOfAny("zzabyycdxx", ["ab","cd"]) = 6 StringUtils.lastIndexOfAny("zzabyycdxx", ["cd","ab"]) = 6 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1 StringUtils.lastIndexOfAny("zzabyycdxx", ["mn",""]) = 10 Parameters: str—the String to check, may be null searchStrs—the Strings to search for, may be null Returns: the last index of any of the Strings, -1 if no match public static java.lang.String substring(java.lang.String str, int start) Gets a substring from the specified String avoiding exceptions. A negative start position can be used to start n characters from the end of the String. A null String will return null. An empty (" ") String will return " ". StringUtils.substring(null, *) = null StringUtils.substring("", *) = "" StringUtils.substring("abc", 0) = "abc" StringUtils.substring("abc", 2) = "c" StringUtils.substring("abc", 4) = "" StringUtils.substring("abc", -2) = "bc" StringUtils.substring("abc", -4) = "abc" Parameters: str—the String to get the substring from, may be null start—the position to start from, negative means count back from the end of the String by this many characters Returns: substring from start position, null if null String input public static java.lang.String substring(java.lang.String str, int start, int end) Iverson_appA.qxd 1/17/05 2:37 PM Page 272 272 Lang Reference Appendix A Gets a substring from the specified String avoiding exceptions. A negative start position can be used to start/end n characters from the end of the String. The returned substring starts with the character in the start position and ends before the end position. All postion counting is zero-based—i.e., to start at the beginning of the string, use start = 0. Negative start and end posi- tions can be used to specify offsets relative to the end of the String. If start is not strictly to the left of end, " " is returned. StringUtils.substring(null, *, *) = null StringUtils.substring("", * , *) = ""; StringUtils.substring("abc", 0, 2) = "ab" StringUtils.substring("abc", 2, 0) = "" StringUtils.substring("abc", 2, 4) = "c" StringUtils.substring("abc", 4, 6) = "" StringUtils.substring("abc", 2, 2) = "" StringUtils.substring("abc", -2, -1) = "b" StringUtils.substring("abc", -4, 2) = "ab" Parameters: str—the String to get the substring from, may be null start—the position to start from, negative means count back from the end of the String by this many characters end—the position to end at (exclusive), negative means count back from the end of the String by this many characters Returns: substring from start position to end positon, null if null String input public static java.lang.String left(java.lang.String str, int len) Gets the leftmost len characters of a String. If len characters are not available, or the String is null, the String will be returned without an exception. An exception is thrown if len is negative. StringUtils.left(null, *) = null StringUtils.left(*, -ve) = "" StringUtils.left("", *) = "" StringUtils.left("abc", 0) = "" StringUtils.left("abc", 2) = "ab" StringUtils.left("abc", 4) = "abc" Parameters: str—the String to get the leftmost characters from, may be null len—the length of the required String, must be zero or positive Returns: the leftmost characters, null if null String input public static java.lang.String right(java.lang.String str, int len) Gets the rightmost len characters of a String. Iverson_appA.qxd 1/17/05 2:37 PM Page 273 org.apache.commons.lang.BooleanUtils 273 If len characters are not available, or the String is null, the String will be returned without an an exception. An exception is thrown if len is negative. StringUtils.right(null, *) = null StringUtils.right(*, -ve) = "" StringUtils.right("", *) = "" StringUtils.right("abc", 0) = "" StringUtils.right("abc", 2) = "bc" StringUtils.right("abc", 4) = "abc" Parameters: str—the String to get the rightmost characters from, may be null len—the length of the required String, must be zero or positive Returns: the rightmost characters, null if null String input public static java.lang.String mid(java.lang.String str, int pos, int len) Gets len characters from the middle of a String. If len characters are not available, the remainder of the String will be returned without an exception. If the String is null, null will be returned. An exception is thrown if len is negative. StringUtils.mid(null, *, *) = null StringUtils.mid(*, *, -ve) = "" StringUtils.mid("", 0, *) = "" StringUtils.mid("abc", 0, 2) = "ab" StringUtils.mid("abc", 0, 4) = "abc" StringUtils.mid("abc", 2, 4) = "c" StringUtils.mid("abc", 4, 2) = "" StringUtils.mid("abc", -2, 2) = "ab" Parameters: str—the String to get the characters from, may be null pos—the position to start from, negative treated as zero len—the length of the required String, must be zero or positive Returns: the middle characters, null if null String input public static java.lang.String substringBefore(java.lang.String str, java.lang.String separator) Gets the substring before the first occurence of a separator. The separator is not returned. A null string input will return null. An empty (" ") string input will return the empty string. A null separator will return the input string. StringUtils.substringBefore(null, *) = null StringUtils.substringBefore("", *) = "" StringUtils.substringBefore("abc", "a") = "" StringUtils.substringBefore("abcba", "b") = "a" StringUtils.substringBefore("abc", "c") = "ab" Iverson_appA.qxd 1/17/05 2:37 PM Page 274 274 Lang Reference Appendix A StringUtils.substringBefore("abc", "d") = "abc" StringUtils.substringBefore("abc", "") = "" StringUtils.substringBefore("abc", null) = "abc" Parameters: str—the String to get a substring from, may be null separator—the String to search for, may be null Returns: the substring before the first occurence of the separator, null if null String input public static java.lang.String substringAfter(java.lang.String str, java.lang.String separator) Gets the substring after the first occurence of a separator. The separator is not returned. A null string input will return null. An empty (" ") string input will return the empty string. A null separator will return the empty string if the input string is not null. StringUtils.substringAfter(null, *) = null StringUtils.substringAfter("", *) = "" StringUtils.substringAfter(*, null) = "" StringUtils.substringAfter("abc", "a") = "bc" StringUtils.substringAfter("abcba", "b") = "cba" StringUtils.substringAfter("abc", "c") = "" StringUtils.substringAfter("abc", "d") = "" StringUtils.substringAfter("abc", "") = "abc" Parameters: str—the String to get a substring from, may be null separator—the String to search for, may be null Returns: the substring after the first occurence of the separator, null if null String input public static java.lang.String substringBeforeLast(java.lang.String str, java.lang.String separator) Gets the substring before the last occurence of a separator. The separator is not returned. A null string input will return null. An empty (" ") string input will return the empty string. An empty or null separator will return the input string. StringUtils.substringBeforeLast(null, *) = null StringUtils.substringBeforeLast("", *) = "" StringUtils.substringBeforeLast("abcba", "b") = "abc" StringUtils.substringBeforeLast("abc", "c") = "ab" StringUtils.substringBeforeLast("a", "a") = "" StringUtils.substringBeforeLast("a", "z") = "a" StringUtils.substringBeforeLast("a", null) = "a" StringUtils.substringBeforeLast("a", "") = "a" Iverson_appA.qxd 1/17/05 2:37 PM Page 275 org.apache.commons.lang.BooleanUtils 275 Parameters: str—the String to get a substring from, may be null separator—the String to search for, may be null Returns: the substring before the last occurence of the separator, null if null String input public static java.lang.String substringAfterLast(java.lang.String str, java.lang.String separator) Gets the substring after the last occurence of a separator. The separator is not returned. A null string input will return null. An empty (" ") string input will return the empty string. An empty or null separator will return the empty string if the input string is not null. StringUtils.substringAfterLast(null, *) = null StringUtils.substringAfterLast("", *) = "" StringUtils.substringAfterLast(*, "") = "" StringUtils.substringAfterLast(*, null) = "" StringUtils.substringAfterLast("abc", "a") = "bc" StringUtils.substringAfterLast("abcba", "b") = "a" StringUtils.substringAfterLast("abc", "c") = "" StringUtils.substringAfterLast("a", "a") = "" StringUtils.substringAfterLast("a", "z") = "" Parameters: str—the String to get a substring from, may be null separator—the String to search for, may be null Returns: the substring after the last occurence of the separator, null if null String input public static java.lang.String substringBetween(java.lang.String str, java.lang.String tag) Gets the String that is nested in between two instances of the same String. A null input String returns null. A null tag returns null. StringUtils.substringBetween(null, *) = null StringUtils.substringBetween("", "") = "" StringUtils.substringBetween("", "tag") = null StringUtils.substringBetween("tagabctag", null) = null StringUtils.substringBetween("tagabctag", "") = "" StringUtils.substringBetween("tagabctag", "tag") = "abc" Parameters: str—the String containing the substring, may be null tag—the String before and after the substring, may be null Returns: the substring, null if no match public static java.lang.String substringBetween(java.lang.String str, java.lang.String open, java.lang.String close) Gets the String that is nested in between two Strings. Only the first match is returned. Iverson_appA.qxd 1/17/05 2:37 PM Page 276 276 Lang Reference Appendix A A null input String returns null. A null open/close returns null (no match). An empty (" ") open/close returns an empty string. StringUtils.substringBetween(null, *, *) = null StringUtils.substringBetween("", "", "") = "" StringUtils.substringBetween("", "", "tag") = null StringUtils.substringBetween("", "tag", "tag") = null StringUtils.substringBetween("yabcz", null, null) = null StringUtils.substringBetween("yabcz", "", "") = "" StringUtils.substringBetween("yabcz", "y", "z") = "abc" StringUtils.substringBetween("yabczyabcz", "y", "z") = "abc" Parameters: str—the String containing the substring, may be null open—the String before the substring, may be null close—the String after the substring, may be null Returns: the substring, null if no match public static java.lang.String[] split(java.lang.String str) Splits the provided text into an array, using whitespace as the separator. Whitespace is defined by Character.isWhitespace(char). The separator is not included in the returned String array. Adjacent separators are treated as one separator. A null input String returns null. StringUtils.split(null) = null StringUtils.split("") = [] StringUtils.split("abc def") = ["abc", "def"] StringUtils.split("abc def") = ["abc", "def"] StringUtils.split(" abc ") = ["abc"] Parameters: str—the String to parse, may be null Returns: an array of parsed Strings, null if null String input public static java.lang.String[] split(java.lang.String str, char separatorChar) Splits the provided text into an array, separator specified. This is an alterna- tive to using StringTokenizer. The separator is not included in the returned String array. Adjacent separators are treated as one separator. A null input String returns null. StringUtils.split(null, *) = null StringUtils.split("", *) = [] StringUtils.split("a.b.c", '.') = ["a", "b", "c"] StringUtils.split("a..b.c", '.') = ["a", "b", "c"] StringUtils.split("a:b:c", '.') = ["a:b:c"] StringUtils.split("a\tb\nc", null) = ["a", "b", "c"] StringUtils.split("a b c", ' ') = ["a", "b", "c"] Iverson_appA.qxd 1/17/05 2:37 PM Page 277 org.apache.commons.lang.BooleanUtils 277 Parameters: str—the String to parse, may be null separatorChar—the character used as the delimiter, null splits on whitespace Returns: an array of parsed Strings, null if null String input public static java.lang.String[] split(java.lang.String str, java.lang.String separatorChars) Splits the provided text into an array, separators specified. This is an alterna- tive to using StringTokenizer. The separator is not included in the returned String array. Adjacent sep- arators are treated as one separator. A null input String returns null. A null separatorChars splits on whitespace. StringUtils.split(null, *) = null StringUtils.split("", *) = [] StringUtils.split("abc def", null) = ["abc", "def"] StringUtils.split("abc def", " ") = ["abc", "def"] StringUtils.split("abc def", " ") = ["abc", "def"] StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"] Parameters: str—the String to parse, may be null separatorChars—the characters used as the delimiters, null splits on whitespace Returns: an array of parsed Strings, null if null String input public static java.lang.String[] split(java.lang.String str, java.lang.String separatorChars, int max) Splits the provided text into an array, separators specified. This is an alterna- tive to using StringTokenizer. The separator is not included in the returned String array. Adjacent sep- arators are treated as one separator. A null input String returns null. A null separatorChars splits on whitespace. StringUtils.split(null, *, *) = null StringUtils.split("", *, *) = [] StringUtils.split("ab de fg", null, 0) = ["ab", "cd", "ef"] StringUtils.split("ab de fg", null, 0) = ["ab", "cd", "ef"] StringUtils.split("ab:cd:ef", ":", 0) = ["ab", "cd", "ef"] StringUtils.split("ab:cd:ef", ":", 2) = ["ab", "cdef"] Parameters: str—the String to parse, may be null separatorChars—the characters used as the delimiters, null splits on whitespace max—the maximum number of elements to include in the array. A zero or negative value implies no limit Iverson_appA.qxd 1/17/05 2:37 PM Page 278 278 Lang Reference Appendix A Returns: an array of parsed Strings, null if null String input public static java.lang.String join(java.lang.Object[] array) Joins the elements of the provided array into a single String containing the provided list of elements. No separator is added to the joined String. Null objects or empty strings within the array are represented by empty strings. StringUtils.join(null) = null StringUtils.join([]) = "" StringUtils.join([null]) = "" StringUtils.join(["a", "b", "c"]) = "abc" StringUtils.join([null, "", "a"]) = "a" Parameters: array—the array of values to join together, may be null Returns: the joined String, null if null array input public static java.lang.String join(java.lang.Object[] array, char separator) Joins the elements of the provided array into a single String containing the provided list of elements. No delimiter is added before or after the list. Null objects or empty strings within the array are represented by empty strings. StringUtils.join(null, *) = null StringUtils.join([], *) = "" StringUtils.join([null], *) = "" StringUtils.join(["a", "b", "c"], ';') = "a;b;c" StringUtils.join(["a", "b", "c"], null) = "abc" StringUtils.join([null, "", "a"], ';') = ";;a" Parameters: array—the array of values to join together, may be null separator—the separator character to use Returns: the joined String, null if null array input public static java.lang.String join(java.lang.Object[] array, java.lang.String separator) Joins the elements of the provided array into a single String containing the provided list of elements. No delimiter is added before or after the list. A null separator is the same as an empty String (" "). Null objects or empty strings within the array are rep- resented by empty strings. StringUtils.join(null, *) = null StringUtils.join([], *) = "" StringUtils.join([null], *) = "" Iverson_appA.qxd 1/17/05 2:37 PM Page 279 org.apache.commons.lang.BooleanUtils 279 StringUtils.join(["a", "b", "c"], "--") = "a--b--c" StringUtils.join(["a", "b", "c"], null) = "abc" StringUtils.join(["a", "b", "c"], "") = "abc" StringUtils.join([null, "", "a"], ',') = ",,a" Parameters: array—the array of values to join together, may be null separator—the separator character to use, null treated as " " Returns: the joined String, null if null array input public static java.lang.String join(java.util.Iterator iterator, char separator) Joins the elements of the provided Iterator into a single String containing the provided elements. No delimiter is added before or after the list. Null objects or empty strings within the iteration are represented by empty strings. See the examples here: join(Object[],char). Parameters: iterator—the Iterator of values to join together, may be null separator—the separator character to use Returns: the joined String, null if null iterator input public static java.lang.String join(java.util.Iterator iterator, java.lang.String separator) Joins the elements of the provided Iterator into a single String containing the provided elements. No delimiter is added before or after the list. A null separator is the same as an empty String (" "). See the examples here: join(Object[],String). Parameters: iterator—the Iterator of values to join together, may be null separator—the separator character to use, null treated as " " Returns: the joined String, null if null iterator input public static java.lang.String deleteWhitespace(java.lang.String str) Deletes all whitespaces from a String as defined by Character.isWhitespace(char). StringUtils.deleteWhitespace(null) = null StringUtils.deleteWhitespace("") = "" StringUtils.deleteWhitespace("abc") = "abc" StringUtils.deleteWhitespace(" ab c ") = "abc" Parameters: str—the String to delete whitespace from, may be null Returns: the String without whitespaces, null if null String input public static java.lang.String replaceOnce(java.lang.String text, java.lang.String repl, java.lang.String with) Iverson_appA.qxd 1/17/05 2:37 PM Page 280 280 Lang Reference Appendix A Replaces a String with another String inside a larger String, once. A null reference passed to this method is a no-op. StringUtils.replaceOnce(null, *, *) = null StringUtils.replaceOnce("", *, *) = "" StringUtils.replaceOnce("aba", null, null) = "aba" StringUtils.replaceOnce("aba", null, null) = "aba" StringUtils.replaceOnce("aba", "a", null) = "aba" StringUtils.replaceOnce("aba", "a", "") = "aba" StringUtils.replaceOnce("aba", "a", "z") = "zba" Parameters: text—text to search and replace in, may be null repl—the String to search for, may be null with—the String to replace with, may be null Returns: the text with any replacements processed, null if null String input See Also: replace(String text, String repl, String with, int max) public static java.lang.String replace(java.lang.String text, java.lang.String repl, java.lang.String with) Replaces all occurances of a String within another String. A null reference passed to this method is a no-op. StringUtils.replace(null, *, *) = null StringUtils.replace("", *, *) = "" StringUtils.replace("aba", null, null) = "aba" StringUtils.replace("aba", null, null) = "aba" StringUtils.replace("aba", "a", null) = "aba" StringUtils.replace("aba", "a", "") = "aba" StringUtils.replace("aba", "a", "z") = "zbz" Parameters: text—text to search and replace in, may be null repl—the String to search for, may be null with—the String to replace with, may be null Returns: the text with any replacements processed, null if null String input See Also: replace(String text, String repl, String with, int max) public static java.lang.String replace(java.lang.String text, java.lang.String repl, java.lang.String with, int max) Replaces a String with another String inside a larger String, for the first max values of the search String. A null reference passed to this method is a no-op. StringUtils.replace(null, *, *, *) = null StringUtils.replace("", *, *, *) = "" StringUtils.replace("abaa", null, null, 1) = "abaa" Iverson_appA.qxd 1/17/05 2:37 PM Page 281 org.apache.commons.lang.BooleanUtils 281 StringUtils.replace("abaa", null, null, 1) = "abaa" StringUtils.replace("abaa", "a", null, 1) = "abaa" StringUtils.replace("abaa", "a", "", 1) = "abaa" StringUtils.replace("abaa", "a", "z", 0) = "abaa" StringUtils.replace("abaa", "a", "z", 1) = "zbaa" StringUtils.replace("abaa", "a", "z", 2) = "zbza" StringUtils.replace("abaa", "a", "z", -1) = "zbzz" Parameters: text—text to search and replace in, may be null repl—the String to search for, may be null with—the String to replace with, may be null max—maximum number of values to replace, or -1 if no maximum Returns: the text with any replacements processed, null if null String input public static java.lang.String replaceChars(java.lang.String str, char searchChar, char replaceChar) Replaces all occurrences of a character in a String with another. This is a null-safe version of String.replace(char, char). A null string input returns null. An empty (" ") string input returns an empty string. StringUtils.replaceChars(null, *, *) = null StringUtils.replaceChars("", *, *) = "" StringUtils.replaceChars("abcba", 'b', 'y') = "aycya" StringUtils.replaceChars("abcba", 'z', 'y') = "abcba" Parameters: str—String to replace characters in, may be null searchChar—the character to search for, may be null replaceChar—the character to replace, may be null Returns: modified String, null if null String input public static java.lang.String replaceChars(java.lang.String str, java.lang.String searchChars, java.lang.String replaceChars) Replaces multiple characters in a String in one go. This method can also be used to delete characters. For example: replaceChars("hello", "ho", "jy") = jelly. A null string input returns null. An empty ("") string input returns an empty string. A null or empty set of search characters returns the input string. The length of the search characters should normally equal the length of the replace characters. If the search characters are longer, then the extra search characters are deleted. If the search characters are shorter, then the extra replace characters are ignored. Iverson_appA.qxd 1/17/05 2:37 PM Page 282 282 Lang Reference Appendix A StringUtils.replaceChars(null, *, *) = null StringUtils.replaceChars("", *, *) = "" StringUtils.replaceChars("abc", null, *) = "abc" StringUtils.replaceChars("abc", "", *) = "abc" StringUtils.replaceChars("abc", "b", null) = "ac" StringUtils.replaceChars("abc", "b", "") = "ac" StringUtils.replaceChars("abcba", "bc", "yz") = "ayzya" StringUtils.replaceChars("abcba", "bc", "y") = "ayya" StringUtils.replaceChars("abcba", "bc", "yzx") = "ayzya" Parameters: str—String to replace characters in, may be null searchChars—a set of characters to search for, may be null replaceChars—a set of characters to replace, may be null Returns: modified String, null if null string input public static java.lang.String overlay(java.lang.String str, java.lang.String overlay, int start, int end) Overlays part of a String with another String. A null string input returns null. A negative index is treated as zero. An index greater than the string length is treated as the string length. The start index is always the smaller of the two indices. StringUtils.overlay(null, *, *, *) = null StringUtils.overlay("", "abc", 0, 0) = "abc" StringUtils.overlay("abcdef", null, 2, 4) = "abef" StringUtils.overlay("abcdef", "", 2, 4) = "abef" StringUtils.overlay("abcdef", "", 4, 2) = "abef" StringUtils.overlay("abcdef", "zzzz", 2, 4) = "abzzzzef" StringUtils.overlay("abcdef", "zzzz", 4, 2) = "abzzzzef" StringUtils.overlay("abcdef", "zzzz", -1, 4) = "zzzzef" StringUtils.overlay("abcdef", "zzzz", 2, 8) = "abzzzz" StringUtils.overlay("abcdef", "zzzz", -2, -3) = "zzzzabcdef" StringUtils.overlay("abcdef", "zzzz", 8, 10) = "abcdefzzzz" Parameters: str—the String to do overlaying in, may be null overlay—the String to overlay, may be null start—the position to start overlaying at end—the position to stop overlaying before Returns: overlayed String, null if null String input public static java.lang.String chomp(java.lang.String str) Removes one newline from end of a String if it’s there, otherwise leave it alone. A newline is "\n", "\r", or "\r\n". NOTE: This method changed in 2.0. It now more closely matches Perl chomp. StringUtils.chomp(null) = null StringUtils.chomp("") = "" Iverson_appA.qxd 1/17/05 2:37 PM Page 283 org.apache.commons.lang.BooleanUtils 283 StringUtils.chomp("abc \r") = "abc " StringUtils.chomp("abc\n") = "abc" StringUtils.chomp("abc\r\n") = "abc" StringUtils.chomp("abc\r\n\r\n") = "abc\r\n" StringUtils.chomp("abc\n\r") = "abc\n" StringUtils.chomp("abc\n\rabc") = "abc\n\rabc" StringUtils.chomp("\r") = "" StringUtils.chomp("\n") = "" StringUtils.chomp("\r\n") = "" Parameters: str—the String to chomp a newline from, may be null Returns: String without newline, null if null String input public static java.lang.String chomp(java.lang.String str, java.lang.String separator) Removes separator from the end of str if it’s there, otherwise leave it alone. NOTE: This method changed in version 2.0. It now more closely matches Perl chomp. For the previous behavior, use substringBeforeLast(String, String). This method uses String.endsWith(String). StringUtils.chomp(null, *) = null StringUtils.chomp("", *) = "" StringUtils.chomp("foobar", "bar") = "foo" StringUtils.chomp("foobar", "baz") = "foobar" StringUtils.chomp("foo", "foo") = "" StringUtils.chomp("foo ", "foo") = "foo" StringUtils.chomp(" foo", "foo") = " " StringUtils.chomp("foo", "foooo") = "foo" StringUtils.chomp("foo", "") = "foo" StringUtils.chomp("foo", null) = "foo" Parameters: str—the String to chomp from, may be null separator—separator String, may be null Returns: String without trailing separator, null if null String input public static java.lang.String chop(java.lang.String str) Remove the last character from a String. If the String ends in \r\n, then remove both of them. StringUtils.chop(null) = null StringUtils.chop("") = "" StringUtils.chop("abc \r") = "abc " StringUtils.chop("abc\n") = "abc" StringUtils.chop("abc\r\n") = "abc" StringUtils.chop("abc") = "ab" StringUtils.chop("abc\nabc") = "abc\nab" StringUtils.chop("a") = "" StringUtils.chop("\r") = "" StringUtils.chop("\n") = "" StringUtils.chop("\r\n") = "" Iverson_appA.qxd 1/17/05 2:37 PM Page 284 284 Lang Reference Appendix A Parameters: str—the String to chop last character from, may be null Returns: String without last character, null if null String input public static java.lang.String repeat(java.lang.String str, int repeat) Repeat a String repeat times to form a new String. StringUtils.repeat(null, 2) = null StringUtils.repeat("", 0) = "" StringUtils.repeat("", 2) = "" StringUtils.repeat("a", 3) = "aaa" StringUtils.repeat("ab", 2) = "abab" StringUtils.repeat("a", -2) = "" Parameters: str—the String to repeat, may be null repeat—number of times to repeat str, negative treated as zero Returns: a new String consisting of the original String repeated, null if null String input public static java.lang.String rightPad(java.lang.String str, int size) Right pad a String with spaces (' '). The String is padded to the size of size. StringUtils.rightPad(null, *) = null StringUtils.rightPad("", 3) = " " StringUtils.rightPad("bat", 3) = "bat" StringUtils.rightPad("bat", 5) = "bat " StringUtils.rightPad("bat", 1) = "bat" StringUtils.rightPad("bat", -1) = "bat" Parameters: str—the String to pad out, may be null size—the size to pad to Returns: right padded String or original String if no padding is neces- sary, null if null String input public static java.lang.String rightPad(java.lang.String str, int size, char padChar) Right pad a String with a specified character. The String is padded to the size of size. StringUtils.rightPad(null, *, *) = null StringUtils.rightPad("", 3, 'z') = "zzz" StringUtils.rightPad("bat", 3, 'z') = "bat" StringUtils.rightPad("bat", 5, 'z') = "batzz" StringUtils.rightPad("bat", 1, 'z') = "bat" StringUtils.rightPad("bat", -1, 'z') = "bat" Iverson_appA.qxd 1/17/05 2:37 PM Page 285 org.apache.commons.lang.BooleanUtils 285 Parameters: str—the String to pad out, may be null size—the size to pad to padChar—the character to pad with Returns: right padded String or original String if no padding is neces- sary, null if null String input public static java.lang.String rightPad(java.lang.String str, int size, java.lang.String padStr) Right pad a String with a specified String. The String is padded to the size of size. StringUtils.rightPad(null, *, *) = null StringUtils.rightPad("", 3, "z") = "zzz" StringUtils.rightPad("bat", 3, "yz") = "bat" StringUtils.rightPad("bat", 5, "yz") = "batyz" StringUtils.rightPad("bat", 8, "yz") = "batyzyzy" StringUtils.rightPad("bat", 1, "yz") = "bat" StringUtils.rightPad("bat", -1, "yz") = "bat" StringUtils.rightPad("bat", 5, null) = "bat " StringUtils.rightPad("bat", 5, "") = "bat " Parameters: str—the String to pad out, may be null size—the size to pad to padStr—the String to pad with, null or empty treated as single space Returns: right padded String or original String if no padding is neces- sary, null if null String input public static java.lang.String leftPad(java.lang.String str, int size) Left pad a String with spaces (' '). The String is padded to the size of size. StringUtils.leftPad(null, *) = null StringUtils.leftPad("", 3) = " " StringUtils.leftPad("bat", 3) = "bat" StringUtils.leftPad("bat", 5) = " bat" StringUtils.leftPad("bat", 1) = "bat" StringUtils.leftPad("bat", -1) = "bat" Parameters: str—the String to pad out, may be null size—the size to pad to Returns: left padded String or original String if no padding is necessary, null if null String input public static java.lang.String leftPad(java.lang.String str, int size, char padChar) Left pad a String with a specified character. Pad to a size of size. Iverson_appA.qxd 1/17/05 2:37 PM Page 286 286 Lang Reference Appendix A StringUtils.leftPad(null, *, *) = null StringUtils.leftPad("", 3, 'z') = "zzz" StringUtils.leftPad("bat", 3, 'z') = "bat" StringUtils.leftPad("bat", 5, 'z') = "zzbat" StringUtils.leftPad("bat", 1, 'z') = "bat" StringUtils.leftPad("bat", -1, 'z') = "bat" Parameters: str—the String to pad out, may be null size—the size to pad to padChar—the character to pad with Returns: left padded String or original String if no padding is necessary, null if null String input public static java.lang.String leftPad(java.lang.String str, int size, java.lang.String padStr) Left pad a String with a specified String. Pad to a size of size. StringUtils.leftPad(null, *, *) = null StringUtils.leftPad("", 3, "z") = "zzz" StringUtils.leftPad("bat", 3, "yz") = "bat" StringUtils.leftPad("bat", 5, "yz") = "yzbat" StringUtils.leftPad("bat", 8, "yz") = "yzyzybat" StringUtils.leftPad("bat", 1, "yz") = "bat" StringUtils.leftPad("bat", -1, "yz") = "bat" StringUtils.leftPad("bat", 5, null) = " bat" StringUtils.leftPad("bat", 5, "") = " bat" Parameters: str—the String to pad out, may be null size—the size to pad to padStr—the String to pad with, null or empty treated as single space Returns: left padded String or original String if no padding is necessary, null if null String input public static java.lang.String center(java.lang.String str, int size) Centers a String in a larger String of size size using the space character (' '). If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero. Equivalent to center(str, size, ""). StringUtils.center(null, *) = null StringUtils.center("", 4) = " " StringUtils.center("ab", -1) = "ab" StringUtils.center("ab", 4) = " ab " StringUtils.center("abcd", 2) = "abcd" StringUtils.center("a", 4) = " a " Parameters: str—the String to center, may be null size—the int size of new String, negative treated as zero Iverson_appA.qxd 1/17/05 2:37 PM Page 287 org.apache.commons.lang.BooleanUtils 287 Returns: centered String, null if null String input public static java.lang.String center(java.lang.String str, int size, char padChar) Centers a String in a larger String of size size. Uses a supplied character as the value to pad the String with. If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero. StringUtils.center(null, *, *) = null StringUtils.center("", 4, ' ') = " " StringUtils.center("ab", -1, ' ') = "ab" StringUtils.center("ab", 4, ' ') = " ab" StringUtils.center("abcd", 2, ' ') = "abcd" StringUtils.center("a", 4, ' ') = " a " StringUtils.center("a", 4, 'y') = "yayy" Parameters: str—the String to center, may be null size—the int size of new String, negative treated as zero padChar—the character to pad the new String with Returns: centered String, null if null String input public static java.lang.String center(java.lang.String str, int size, java.lang.String padStr) Centers a String in a larger String of size size. Uses a supplied String as the value to pad the String with. If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero. StringUtils.center(null, *, *) = null StringUtils.center("", 4, " ") = " " StringUtils.center("ab", -1, " ") = "ab" StringUtils.center("ab", 4, " ") = " ab" StringUtils.center("abcd", 2, " ") = "abcd" StringUtils.center("a", 4, " ") = " a " StringUtils.center("a", 4, "yz") = "yayz" StringUtils.center("abc", 7, null) = " abc " StringUtils.center("abc", 7, "") = " abc " Parameters: str—the String to center, may be null size—the int size of new String, negative treated as zero padStr—the String to pad the new String with, must not be null or empty Returns: centered String, null if null String input Throws: java.lang.IllegalArgumentException—if padStr is null or empty public static java.lang.String upperCase(java.lang.String str) Converts a String to upper case as per String.toUpperCase(). Iverson_appA.qxd 1/17/05 2:37 PM Page 288 288 Lang Reference Appendix A A null input String returns null. StringUtils.upperCase(null) = null StringUtils.upperCase("") = "" StringUtils.upperCase("aBc") = "ABC" Parameters: str—the String to upper case, may be null Returns: the upper cased String, null if null String input public static java.lang.String lowerCase(java.lang.String str) Converts a String to lower case as per String.toLowerCase(). A null input String returns null. StringUtils.lowerCase(null) = null StringUtils.lowerCase("") = "" StringUtils.lowerCase("aBc") = "abc" Parameters: str—the String to lower case, may be null Returns: the lower cased String, null if null String input public static java.lang.String capitalize(java.lang.String str) Capitalizes a String changing the first letter to title case as per Character.toTitleCase(char). No other letters are changed. For a word based algorithm, see WordUtils.capitalize(String). A null input String returns null. StringUtils.capitalize(null) = null StringUtils.capitalize("") = "" StringUtils.capitalize("cat") = "Cat" StringUtils.capitalize("cAt") = "CAt" Parameters: str—the String to capitalize, may be null Returns: the capitalized String, null if null String input See Also: WordUtils.capitalize(String), uncapitalize(String) public static java.lang.String uncapitalize(java.lang.String str) Uncapitalizes a String changing the first letter to title case as per Character.toLowerCase(char). No other letters are changed. For a word based algorithm, see WordUtils.uncapitalize(String). A null input String returns null. StringUtils.uncapitalize(null) = null StringUtils.uncapitalize("") = "" StringUtils.uncapitalize("Cat") = "cat" StringUtils.uncapitalize("CAT") = "cAT" Iverson_appA.qxd 1/17/05 2:37 PM Page 289 org.apache.commons.lang.BooleanUtils 289 Parameters: str—the String to uncapitalize, may be null Returns: the uncapitalized String, null if null String input See Also: WordUtils.uncapitalize(String), capitalize(String) public static java.lang.String swapCase(java.lang.String str) Swaps the case of a String changing upper and title case to lower case, and lower case to upper case. ☞ Upper case character converts to Lower case ☞ Title case character converts to Lower case ☞ Lower case character converts to Upper case For a word based algorithm, see WordUtils.swapCase(String). A null input String returns null. StringUtils.swapCase(null) = null StringUtils.swapCase("") = "" StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone" NOTE: This method changed in Lang version 2.0. It no longer performs a word based algorithm. If you only use ASCII, you will notice no change. That functionality is available in WordUtils. Parameters: str—the String to swap case, may be null Returns: the changed String, null if null String input public static int countMatches(java.lang.String str, java.lang.String sub) Counts how many times the substring appears in the larger String. A null or empty (" ") String input returns 0. StringUtils.countMatches(null, *) = 0 StringUtils.countMatches("", *) = 0 StringUtils.countMatches("abba", null) = 0 StringUtils.countMatches("abba", "") = 0 StringUtils.countMatches("abba", "a") = 2 StringUtils.countMatches("abba", "ab") = 1 StringUtils.countMatches("abba", "xxx") = 0 Parameters: str—the String to check, may be null sub—the substring to count, may be null Returns: the number of occurences, 0 if either String is null public static boolean isAlpha(java.lang.String str) Checks if the String contains only unicode letters. null will return false. An empty String (" ") will return true. Iverson_appA.qxd 1/17/05 2:37 PM Page 290 290 Lang Reference Appendix A StringUtils.isAlpha(null) = false StringUtils.isAlpha("") = true StringUtils.isAlpha(" ") = false StringUtils.isAlpha("abc") = true StringUtils.isAlpha("ab2c") = false StringUtils.isAlpha("ab-c") = false Parameters: str—the String to check, may be null Returns: true if only contains letters, and is non-null public static boolean isAlphaSpace(java.lang.String str) Checks if the String contains only unicode letters and space (' '). null will return false An empty String (" ") will return true. StringUtils.isAlphaSpace(null) = false StringUtils.isAlphaSpace("") = true StringUtils.isAlphaSpace(" ") = true StringUtils.isAlphaSpace("abc") = true StringUtils.isAlphaSpace("ab c") = true StringUtils.isAlphaSpace("ab2c") = false StringUtils.isAlphaSpace("ab-c") = false Parameters: str—the String to check, may be null Returns: true if only contains letters and space, and is non-null public static boolean isAlphanumeric(java.lang.String str) Checks if the String contains only unicode letters or digits. null will return false. An empty String (" ") will return true. StringUtils.isAlphanumeric(null) = false StringUtils.isAlphanumeric("") = true StringUtils.isAlphanumeric(" ") = false StringUtils.isAlphanumeric("abc") = true StringUtils.isAlphanumeric("ab c") = false StringUtils.isAlphanumeric("ab2c") = true StringUtils.isAlphanumeric("ab-c") = false Parameters: str—the String to check, may be null Returns: true if only contains letters or digits, and is non-null public static boolean isAlphanumericSpace(java.lang.String str) Checks if the String contains only unicode letters, digits or space (' '). null will return false. An empty String (" ") will return true. StringUtils.isAlphanumeric(null) = false StringUtils.isAlphanumeric("") = true Iverson_appA.qxd 1/17/05 2:37 PM Page 291 org.apache.commons.lang.BooleanUtils 291 StringUtils.isAlphanumeric(" ") = true StringUtils.isAlphanumeric("abc") = true StringUtils.isAlphanumeric("ab c") = true StringUtils.isAlphanumeric("ab2c") = true StringUtils.isAlphanumeric("ab-c") = false Parameters: str—the String to check, may be null Returns: true if only contains letters, digits or space, and is non-null public static boolean isNumeric(java.lang.String str) Checks if the String contains only unicode digits. A decimal point is not a uni- code digit and returns false. null will return false. An empty String (" ") will return true. StringUtils.isNumeric(null) = false StringUtils.isNumeric("") = true StringUtils.isNumeric(" ") = false StringUtils.isNumeric("123") = true StringUtils.isNumeric("12 3") = false StringUtils.isNumeric("ab2c") = false StringUtils.isNumeric("12-3") = false StringUtils.isNumeric("12.3") = false Parameters: str—the String to check, may be null Returns: true if only contains digits, and is non-null public static boolean isNumericSpace(java.lang.String str) Checks if the String contains only unicode digits or space (' '). A decimal point is not a unicode digit and returns false. null will return false. An empty String (" ") will return true. StringUtils.isNumeric(null) = false StringUtils.isNumeric("") = true StringUtils.isNumeric(" ") = true StringUtils.isNumeric("123") = true StringUtils.isNumeric("12 3") = true StringUtils.isNumeric("ab2c") = false StringUtils.isNumeric("12-3") = false StringUtils.isNumeric("12.3") = false Parameters: str—the String to check, may be null Returns: true if only contains digits or space, and is non-null public static boolean isWhitespace(java.lang.String str) Checks if the String contains only whitespace. null will return false. An empty String (" ") will return true. Iverson_appA.qxd 1/17/05 2:37 PM Page 292 292 Lang Reference Appendix A StringUtils.isWhitespace(null) = false StringUtils.isWhitespace("") = true StringUtils.isWhitespace(" ") = true StringUtils.isWhitespace("abc") = false StringUtils.isWhitespace("ab2c") = false StringUtils.isWhitespace("ab-c") = false Parameters: str—the String to check, may be null Returns: true if only contains whitespace, and is non-null public static java.lang.String defaultString(java.lang.String str) Returns either the passed in String, or if the String is null, an empty String (" "). StringUtils.defaultString(null) = "" StringUtils.defaultString("") = "" StringUtils.defaultString("bat") = "bat" Parameters: str—the String to check, may be null Returns: the passed in String, or the empty String if it was null See Also: ObjectUtils.toString(Object), String.valueOf(Object) public static java.lang.String defaultString(java.lang.String str, java.lang.String defaultStr) Returns either the passed in String, or if the String is null, an empty String (" "). StringUtils.defaultString(null, "null") = "null" StringUtils.defaultString("", "null") = "" StringUtils.defaultString("bat", "null") = "bat" Parameters: str—the String to check, may be null defaultStr—the default String to return if the input is null, may be null Returns: the passed in String, or the default if it was null See Also: ObjectUtils.toString(Object,String), String.valueOf(Object) public static java.lang.String reverse(java.lang.String str) Reverses a String as per StringBuffer.reverse(). null String returns null. StringUtils.reverse(null) = null StringUtils.reverse("") = "" StringUtils.reverse("bat") = "tab" Parameters: str—the String to reverse, may be null Returns: the reversed String, null if null String input Iverson_appA.qxd 1/17/05 2:37 PM Page 293 org.apache.commons.lang.BooleanUtils 293 public static java.lang.String reverseDelimited(java.lang.String str, char separatorChar) Reverses a String that is delimited by a specific character. The Strings between the delimiters are not reversed. Thus java.lang.String becomes String.lang.java (if the delimiter is '.'). StringUtils.reverseDelimited(null, *) = null StringUtils.reverseDelimited("", *) = "" StringUtils.reverseDelimited("a.b.c", 'x') = "a.b.c" StringUtils.reverseDelimited("a.b.c", ".") = "c.b.a" Parameters: str—the String to reverse, may be null separatorChar—the separator character to use Returns: the reversed String, null if null String input public static java.lang.String abbreviate(java.lang.String str, int maxWidth) Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "Now is the time for. . . " Specifically: ☞ If str is less than maxWidth characters long, return it. ☞ Else abbreviate it to (substring(str, 0, max-3) + "..."). ☞ If maxWidth is less than 4, throw an IllegalArgumentException. ☞ In no case will it return a String of length greater than maxWidth. StringUtils.abbreviate(null, *) = null StringUtils.abbreviate("", 4) = "" StringUtils.abbreviate("abcdefg", 6) = "abc..." StringUtils.abbreviate("abcdefg", 7) = "abcdefg" StringUtils.abbreviate("abcdefg", 8) = "abcdefg" StringUtils.abbreviate("abcdefg", 4) = "a..." StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException Parameters: str—the String to check, may be null maxWidth—maximum length of result String, must be at least 4 Returns: abbreviated String, null if null String input Throws: java.lang.IllegalArgumentException—if the width is too small public static java.lang.String abbreviate(java.lang.String str, int offset, int maxWidth) Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into ". . . is the time for . . ." Works like abbreviate(String, int), but allows you to specify a "left edge" offset. Note that this left edge is not necessarily going to be the leftmost char- acter in the result, or the first character following the ellipses, but it will appear somewhere in the result. Iverson_appA.qxd 1/17/05 2:37 PM Page 294 294 Lang Reference Appendix A In no case will it return a String of length greater than maxWidth. StringUtils.abbreviate(null, *, *) = null StringUtils.abbreviate("", 0, 4) = "" StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 0, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 1, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 4, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 5, 10) = "...fghi..." StringUtils.abbreviate("abcdefghijklmno", 6, 10) = "...ghij..." StringUtils.abbreviate("abcdefghijklmno", 8, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghij", 0, 3) = IllegalArgumentException StringUtils.abbreviate("abcdefghij", 5, 6) = IllegalArgumentException Parameters: str—the String to check, may be null offset—left edge of source String maxWidth—maximum length of result String, must be at least 4 Returns: abbreviated String, null if null String input Throws: java.lang.IllegalArgumentException—if the width is too small public static java.lang.String difference(java.lang.String str1, java.lang.String str2) Compares two Strings, and returns the portion where they differ. (More pre- cisely, return the remainder of the second String, starting from where it’s dif- ferent from the first.) For example, difference("i am a machine", "i am a robot") -> "robot". StringUtils.difference(null, null) = null StringUtils.difference("", "") = "" StringUtils.difference("", "abc") = "abc" StringUtils.difference("abc", "") = "" StringUtils.difference("abc", "abc") = "" StringUtils.difference("ab", "abxyz") = "xyz" StringUtils.difference("abcde", "abxyz") = "xyz" StringUtils.difference("abcde", "xyz") = "xyz" Parameters: str1—the first String, may be null str2—the second String, may be null Returns: the portion of str2 where it differs from str1; returns the empty String if they are equal public static int indexOfDifference(java.lang.String str1, java.lang.String str2) Compares two Strings, and returns the index at which the Strings begin to differ. For example, indexOfDifference("i am a machine", "i am a robot") -> 7 Iverson_appA.qxd 1/17/05 2:37 PM Page 295 org.apache.commons.lang.BooleanUtils 295 StringUtils.indexOfDifference(null, null) = -1 StringUtils.indexOfDifference("", "") = -1 StringUtils.indexOfDifference("", "abc") = 0 StringUtils.indexOfDifference("abc", "") = 0 StringUtils.indexOfDifference("abc", "abc") = -1 StringUtils.indexOfDifference("ab", "abxyz") = 2 StringUtils.indexOfDifference("abcde", "abxyz") = 2 StringUtils.indexOfDifference("abcde", "xyz") = 0 Parameters: str1—the first String, may be null str2—the second String, may be null Returns: the index where str2 and str1 begin to differ; -1 if they are equal public static int getLevenshteinDistance(java.lang.String s, java.lang.String t) Find the Levenshtein distance between two Strings. This is the number of changes needed to change one String into another, where each change is a single character modification (deletion, insertion or substitution). This implementation of the Levenshtein distance algorithm is from http://www.merriampark.com/ld.htm StringUtils.getLevenshteinDistance(null, *) = IllegalArgumentException StringUtils.getLevenshteinDistance(*, null) = IllegalArgumentException StringUtils.getLevenshteinDistance("","") = 0 StringUtils.getLevenshteinDistance("","a") = 1 StringUtils.getLevenshteinDistance("aaapppp", "") = 7 StringUtils.getLevenshteinDistance("frog", "fog") = 1 StringUtils.getLevenshteinDistance("fly", "ant") = 3 StringUtils.getLevenshteinDistance("elephant", "hippo") = 7 StringUtils.getLevenshteinDistance("hippo", "elephant") = 7 StringUtils.getLevenshteinDistance("hippo", "zzzzzzzz") = 8 StringUtils.getLevenshteinDistance("hello", "hallo") = 1 Parameters: s—the first String, must not be null t—the second String, must not be null Returns: result distance Throws: java.lang.IllegalArgumentException—if either String input null org.apache.commons.lang.SystemUtils Helpers for java.lang.System. If a system property cannot be read due to security restrictions, the cor- responding field in this class will be set to null and a message will be written to System.err. Field Detail public static final java.lang.String FILE_ENCODING Iverson_appA.qxd 1/17/05 2:37 PM Page 296 296 Lang Reference Appendix A The file.encoding System Property. File encoding, such as Cp1252. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2. public static final java.lang.String FILE_SEPARATOR The file.separator System Property. File separator ("/" on UNIX). Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1. public static final java.lang.String JAVA_CLASS_PATH The java.class.path System Property. Java class path. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1. public static final java.lang.String JAVA_CLASS_VERSION The java.class.version System Property. Java class format version number. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.1. public static final java.lang.String JAVA_COMPILER The java.compiler System Property. Name of JIT compiler to use. First in JDK version 1.2. Not used in Sun JDKs after 1.2. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2. Not used in Sun versions after 1.2. public static final java.lang.String JAVA_EXT_DIRS The java.ext.dirs System Property. Path of extension directory or directories. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.3 public static final java.lang.String JAVA_HOME The java.home System Property. Java installation directory. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String JAVA_IO_TMPDIR Iverson_appA.qxd 1/17/05 2:37 PM Page 297 org.apache.commons.lang.BooleanUtils 297 The java.io.tmpdir System Property. Default temp file path. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_LIBRARY_PATH The java.library.path System Property. List of paths to search when loading libraries. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_RUNTIME_NAME The java.runtime.name System Property. Java Runtime Environment name. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.3 public static final java.lang.String JAVA_RUNTIME_VERSION The java.runtime.version System Property. Java Runtime Environment ver- sion. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.3 public static final java.lang.String JAVA_SPECIFICATION_NAME The java.specification.name System Property. Java Runtime Environment specification name. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_SPECIFICATION_VENDOR The java.specification.vendor System Property. Java Runtime Environment specification vendor. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_SPECIFICATION_VERSION The java.specification.version System Property. Java Runtime Environment specification version. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.3 public static final java.lang.String JAVA_VENDOR Iverson_appA.qxd 1/17/05 2:37 PM Page 298 298 Lang Reference Appendix A The java.vendor System Property. Java vendor-specific string. Defaults to null if the runtime does not have security access to read this property or the prop- erty does not exist. Since: Java 1.1 public static final java.lang.String JAVA_VENDOR_URL The java.vendor.url System Property. Java vendor URL. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String JAVA_VERSION The java.version System Property. Java version number. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String JAVA_VM_INFO The java.vm.info System Property. Java Virtual Machine implementation info. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_NAME The java.vm.name System Property. Java Virtual Machine implementation name. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_SPECIFICATION_NAME The java.vm.specification.name System Property. Java Virtual Machine speci- fication name. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_SPECIFICATION_VENDOR The java.vm.specification.vendor System Property. Java Virtual Machine specification vendor. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_SPECIFICATION_VERSION Iverson_appA.qxd 1/17/05 2:37 PM Page 299 org.apache.commons.lang.BooleanUtils 299 The java.vm.specification.version System Property. Java Virtual Machine specification version. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_VENDOR The java.vm.vendor System Property. Java Virtual Machine implementation vendor. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String JAVA_VM_VERSION The java.vm.version System Property. Java Virtual Machine implementation version. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.2 public static final java.lang.String LINE_SEPARATOR The line.separator System Property. Line separator ("\n<" on UNIX). Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.1 public static final java.lang.String OS_ARCH The os.arch System Property. Operating system architecture. Defaults to null if the runtime does not have security access to read this property or the prop- erty does not exist. Since: Java 1.1 public static final java.lang.String OS_NAME The os.name System Property. Operating system name. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String OS_VERSION The os.version System Property. Operating system version. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String PATH_SEPARATOR Iverson_appA.qxd 1/17/05 2:37 PM Page 300 300 Lang Reference Appendix A The path.separator System Property. Path separator (":" on UNIX). Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String USER_COUNTRY The user.country or user.region System Property. User’s country code, such as GB. First in JDK version 1.2 as user.region. Renamed to user.country in 1.4. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.2 public static final java.lang.String USER_DIR The user.dir System Property. User’s current working directory. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String USER_HOME The user.home System Property. User’s home directory. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final java.lang.String USER_LANGUAGE The user.language System Property. User’s language code, such as 'en'. Defaults to null if the runtime does not have security access to read this prop- erty or the property does not exist. Since: Java 1.2 public static final java.lang.String USER_NAME The user.name System Property. User’s account name. Defaults to null if the runtime does not have security access to read this property or the property does not exist. Since: Java 1.1 public static final float JAVA_VERSION_FLOAT Gets the Java version as a float. Example return values: ☞ 1.2f for JDK 1.2 ☞ 1.31f for JDK 1.3.1 Iverson_appA.qxd 1/17/05 2:37 PM Page 301 org.apache.commons.lang.BooleanUtils 301 The field will return zero if JAVA_VERSION is null. public static final int JAVA_VERSION_INT Gets the Java version as an int. Example return values: ☞ 120 for JDK 1.2 ☞ 131 for JDK 1.3.1 The field will return zero if JAVA_VERSION is null. public static final boolean IS_JAVA_1_1 Is true if this is Java version 1.1 (also 1.1.x versions). The field will return false if JAVA_VERSION is null. public static final boolean IS_JAVA_1_2 Is true if this is Java version 1.2 (also 1.2.x versions). The field will return false if JAVA_VERSION is null. public static final boolean IS_JAVA_1_3 Is true if this is Java version 1.3 (also 1.3.x versions). The field will return false if JAVA_VERSION is null. public static final boolean IS_JAVA_1_4 Is true if this is Java version 1.4 (also 1.4.x versions). The field will return false if JAVA_VERSION is null. public static final boolean IS_JAVA_1_5 Is true if this is Java version 1.5 (also 1.5.x versions). The field will return false if JAVA_VERSION is null. public static final boolean IS_OS_AIX Is true if this is AIX. The field will return false if OS_NAME is null. public static final boolean IS_OS_HP_UX Is true if this is HP-UX. The field will return false if OS_NAME is null. public static final boolean IS_OS_IRIX Is true if this is Irix. The field will return false if OS_NAME is null. public static final boolean IS_OS_LINUX Iverson_appA.qxd 1/17/05 2:37 PM Page 302 302 Lang Reference Appendix A Is true if this is Linux. The field will return false if OS_NAME is null. public static final boolean IS_OS_MAC Is true if this is Mac. The field will return false if OS_NAME is null. public static final boolean IS_OS_MAC_OSX Is true if this is MacOSX. The field will return false if OS_NAME is null. public static final boolean IS_OS_OS2 Is true if this is OS/2. The field will return false if OS_NAME is null. public static final boolean IS_OS_SOLARIS Is true if this is Solaris. The field will return false if OS_NAME is null. public static final boolean IS_OS_SUN_OS Is true if this is SunOS. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS Is true if this is Windows. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_2000 Is true if this is Windows 2000. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_95 Is true if this is Windows 95. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_98 Is true if this is Windows 98. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_ME Is true if this is Windows ME. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_NT Is true if this is Windows NT. The field will return false if OS_NAME is null. public static final boolean IS_OS_WINDOWS_XP Is true if this is Windows XP. The field will return false if OS_NAME is null. Iverson_appA.qxd 1/17/05 2:37 PM Page 303 org.apache.commons.lang.BooleanUtils 303 Constructor Detail public SystemUtils() SystemUtils instances should NOT be constructed in standard programming. Instead, the class should be used as SystemUtils.FILE_SEPARATOR. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static boolean isJavaVersionAtLeast(float requiredVersion) Is the Java version at least the requested version. Example input: ☞ 1.2f to test for JDK 1.2 ☞ 1.31f to test for JDK 1.3.1 Parameters: requiredVersion—the required version, for example 1.31f Returns: true if the actual version is equal or greater than the required version public static boolean isJavaVersionAtLeast(int requiredVersion) Is the Java version at least the requested version. Example input: ☞ 120 to test for JDK 1.2 or greater ☞ 131 to test for JDK 1.3.1 or greater Parameters: requiredVersion—the required version, for example 131 Returns: true if the actual version is equal or greater than the required version org.apache.commons.lang.Validate Assists in validating arguments. The class is based along the lines of JUnit. If an argument value is deemed invalid, an IllegalArgumentException is thrown. For example: Validate.isTrue( i>0, "The value must be greater than zero: ", i); Validate.notNull( surname, "The surname must not be null"); Constructor Detail public Validate() Constructor. This class should not normally be instantiated. Iverson_appA.qxd 1/17/05 2:37 PM Page 304 304 Lang Reference Appendix A Method Detail public static void isTrue(boolean expression, java.lang.String message, java.lang.Object value) Validate an argument, throwing IllegalArgumentException if the test result is false. This is used when validating according to an arbitrary boolean expres- sion, such as validating a primitive number or using your own custom valida- tion expression. Validate.isTrue( myObject.isOk(), "The object is not OK: ", myObject); For performance reasons, the object is passed as a separate parameter and appended to the message string only in the case of an error. Parameters: expression—a boolean expression message—the exception message you would like to see if the expression is false value—the value to append to the message in case of error Throws: java.lang.IllegalArgumentException—if expression is false public static void isTrue(boolean expression, java.lang.String message, long value) Validate an argument, throwing IllegalArgumentException if the test result is false. This is used when validating according to an arbitrary boolean expres- sion, such as validating a primitive number or using your own custom valida- tion expression. Validate.isTrue( i<0, "The value must be greater than zero: ", i); For performance reasons, the object is passed as a separate parameter and appended to the message string only in the case of an error. Parameters: expression—a boolean expression message—the exception message you would like to see if the expression is false value—the value to append to the message in case of error Throws: java.lang.IllegalArgumentException—if expression is false public static void isTrue(boolean expression, java.lang.String message, double value) Validate an argument, throwing IllegalArgumentException if the test result is false. This is used when validating according to an arbitrary boolean expres- sion, such as validating a primitive number or using your own custom valida- tion expression. Validate.isTrue( d>0.0, "The value must be greater than zero: ", d); Iverson_appA.qxd 1/17/05 2:37 PM Page 305 org.apache.commons.lang.BooleanUtils 305 For performance reasons, the object is passed as a separate parameter and appended to the message string only in the case of an error. Parameters: expression—a boolean expression message—the exception message you would like to see if the expression is false value—the value to append to the message in case of error Throws: java.lang.IllegalArgumentException—if expression is false public static void isTrue(boolean expression, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the test result is false. This is used when validating according to an arbitrary boolean expres- sion, such as validating a primitive number or using your own custom valida- tion expression. Validate.isTrue( (i>0), "The value must be greater than zero"); Validate.isTrue( myObject.isOk(), "The object is not OK"); For performance reasons, the message string should not involve a string append, instead use the isTrue(boolean, String, Object) method. Parameters: expression—a boolean expression message—the exception message you would like to see if the expression is false Throws: java.lang.IllegalArgumentException—if expression is false public static void isTrue(boolean expression) Validate an argument, throwing IllegalArgumentException if the test result is false. This is used when validating according to an arbitrary boolean expres- sion, such as validating a primitive number or using your own custom valida- tion expression. Validate.isTrue( i>0 ); Validate.isTrue( myObject.isOk() ); The message in the exception is 'The validated expression is false'. Parameters: expression—a boolean expression Throws: java.lang.IllegalArgumentException—if expression is false public static void notNull(java.lang.Object object, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument is null. Iverson_appA.qxd 1/17/05 2:37 PM Page 306 306 Lang Reference Appendix A Validate.notNull(myObject, "The object must not be null"); Parameters: object—the object to check is not null message—the exception message you would like to see if the object is null Throws: java.lang.IllegalArgumentException—if the object is null public static void notNull(java.lang.Object object) Validate an argument, throwing IllegalArgumentException if the argument is null. Validate.notNull(myObject); The message in the exception is 'The validated object is null'. Parameters: object—the object to check is not null Throws: java.lang.IllegalArgumentException—if the object is null public static void notEmpty(java.lang.Object[] array, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument array is empty (null or no elements). Validate.notEmpty(myArray, "The array must not be empty"); Parameters: array—the array to check is not empty message—the exception message you would like to see if the array is empty Throws: java.lang.IllegalArgumentException—if the array is empty public static void notEmpty(java.lang.Object[] array) Validate an argument, throwing IllegalArgumentException if the argument array is empty (null or no elements). Validate.notEmpty(myArray); The message in the exception is 'The validated array is empty'. Parameters: array—the array to check is not empty Throws: java.lang.IllegalArgumentException—if the array is empty public static void notEmpty(java.util.Collection collection, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument Collection is empty (null or no elements). Validate.notEmpty(myCollection, "The collection must not be empty"); Parameters: collection—the collection to check is not empty Iverson_appA.qxd 1/17/05 2:37 PM Page 307 org.apache.commons.lang.BooleanUtils 307 message—the exception message you would like to see if the collection is empty Throws: java.lang.IllegalArgumentException—if the collection is empty public static void notEmpty(java.util.Collection collection) Validate an argument, throwing IllegalArgumentException if the argument Collection is empty (null or no elements). Validate.notEmpty(myCollection); The message in the exception is 'The validated collection is empty'. Parameters: collection—the collection to check is not empty Throws: java.lang.IllegalArgumentException—if the collection is empty public static void notEmpty(java.util.Map map, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument Map is empty (null or no elements). Validate.notEmpty(myMap, "The collection must not be empty"); Parameters: map—the map to check is not empty message—the exception message you would like to see if the map is empty Throws: java.lang.IllegalArgumentException—if the map is empty public static void notEmpty(java.util.Map map) Validate an argument, throwing IllegalArgumentException if the argument Map is empty (null or no elements). Validate.notEmpty(myMap); The message in the exception is 'The validated map is empty'. Parameters: map—the map to check is not empty Throws: java.lang.IllegalArgumentException—if the map is empty public static void notEmpty(java.lang.String string, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument String is empty (null or zero length). Validate.notEmpty(myString, "The string must not be empty"); Parameters: string—the string to check is not empty message—the exception message you would like to see if the string is empty Throws: java.lang.IllegalArgumentException—if the string is empty Iverson_appA.qxd 1/17/05 2:37 PM Page 308 308 Lang Reference Appendix A public static void notEmpty(java.lang.String string) Validate an argument, throwing IllegalArgumentException if the argument String is empty (null or zero length). Validate.notEmpty(myString); The message in the exception is 'The validated string is empty'. Parameters: string—the string to check is not empty Throws: java.lang.IllegalArgumentException—if the string is empty public static void noNullElements(java.lang.Object[] array, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument array has null elements or is null. Validate.notEmpty(myArray, "The array must not contain null elements"); Parameters: array—the array to check message—the exception message if the array has null elements Throws: java.lang.IllegalArgumentException—if the array has null elements or is null public static void noNullElements(java.lang.Object[] array) Validate an argument, throwing IllegalArgumentException if the argument array has null elements or is null. Validate.notEmpty(myArray); The message in the exception is 'The validated array contains null element at index:'. Parameters: array—the array to check Throws: java.lang.IllegalArgumentException—if the array has null elements or is null public static void noNullElements(java.util.Collection collection, java.lang.String message) Validate an argument, throwing IllegalArgumentException if the argument collection has null elements or is null. Validate.notEmpty(myCollection, "The collection must not contain null elements"); Parameters: collection—the collection to check message—the exception message if the array has null elements Iverson_appA.qxd 1/17/05 2:37 PM Page 309 org.apache.commons.lang.BooleanUtils 309 Throws: java.lang.IllegalArgumentException—if the collection has null elements or is null public static void noNullElements(java.util.Collection collection) Validate an argument, throwing IllegalArgumentException if the argument collection has null elements or is null. Validate.notEmpty(myCollection); The message in the exception is 'The validated collection contains null element at index:'. Parameters: collection—the collection to check Throws: java.lang.IllegalArgumentException—if the collection has null elements or is null org.apache.commons.lang.WordUtils Operations on Strings that contain words. This class tries to handle null input gracefully. An exception will not be thrown for a null input. Each method docu- ments its behavior in more detail. Constructor Detail public WordUtils() WordWrapUtils instances should NOT be constructed in standard programming. Instead, the class should be used as WordWrapUtils.wrap("foo bar", 20);. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String wrap(java.lang.String str, int wrapLength) Wraps a single line of text, identifying words by ' '. New lines will be separated by the system property line separator. Very long words, such as URLs, will not be wrapped. Leading spaces on a new line are stripped. Trailing spaces are not stripped. WordUtils.wrap(null, *) = null WordUtils.wrap("", *) = "" Parameters: str—the String to be word wrapped, may be null wrapLength—the column to wrap the words at, less than 1 is treated as 1 Iverson_appA.qxd 1/17/05 2:37 PM Page 310 310 Lang Reference Appendix A Returns: a line with newlines inserted, null if null input public static java.lang.String wrap(java.lang.String str, int wrapLength, java.lang.String newLineStr, boolean wrapLongWords) Wraps a single line of text, identifying words by ' '. Leading spaces on a new line are stripped. Trailing spaces are not stripped. WordUtils.wrap(null, *, *, *) = null WordUtils.wrap("", *, *, *) = "" Parameters: str—the String to be word wrapped, may be null wrapLength—the column to wrap the words at, less than 1 is treated as 1 newLineStr—the string to insert for a new line, null uses the system prop- erty line separator wrapLongWords—true if long words (such as URLs) should be wrapped Returns: a line with newlines inserted, null if null input public static java.lang.String capitalize(java.lang.String str) Capitalizes all the whitespace separated words in a String. Only the first letter of each word is changed. To change all letters to the capitalized case, by Character.isWhitespace(char). A null input String returns null. Capitalization uses the unicode title case, normally equivalent to upper case. capitalizeFully(String). Whitespace defined use is WordUtils.capitalize(null) = null WordUtils.capitalize("") = "" WordUtils.capitalize("i am FINE") = "I Am FINE" Parameters: str—the String to capitalize, may be null Returns: capitalized String, null if null String input See Also: uncapitalize(String), capitalizeFully(String) public static java.lang.String capitalizeFully(java.lang.String str) Capitalizes all the whitespace separated words in a String. All letters are changed, so the resulting string will be fully changed. Whitespace is defined by Character.isWhitespace(char). A null input String returns null. Capitalization uses the unicode title case, normally equivalent to upper case. WordUtils.capitalize(null) = null WordUtils.capitalize("") = "" WordUtils.capitalize("i am FINE") = "I Am Fine" Parameters: str—the String to capitalize, may be null Iverson_appA.qxd 1/17/05 2:37 PM Page 311 org.apache.commons.lang.time 311 Returns: capitalized String, null if null String input public static java.lang.String uncapitalize(java.lang.String str) Uncapitalizes all the whitespace separated words in a String. Only the first letter of each word is changed. Whitespace is defined by Character.isWhitespace(char). A null input String returns null. WordUtils.uncapitalize(null) = null WordUtils.uncapitalize("") = "" WordUtils.uncapitalize("I Am FINE") = "i am fINE" Parameters: str—the String to uncapitalize, may be null Returns: uncapitalized String, null if null String input See Also: capitalize(String) public static java.lang.String swapCase(java.lang.String str) Swaps the case of a String using a word based algorithm. ☞ Upper case character converts to Lower case ☞ Title case character converts to Lower case ☞ Lower case character after Whitespace or at start converts to Title case ☞ Other Lower case character converts to Upper case Whitespace is defined by Character.isWhitespace(char). A null input String returns null. StringUtils.swapCase(null) = null StringUtils.swapCase("") = "" StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone" Parameters: str—the String to swap case, may be null Returns: the changed String, null if null String input ORG.APACHE.COMMONS.LANG.TIME Provides classes and methods to work with dates and durations. This includes: ☞ DateUtils—A set of public utility methods for working with dates ☞ FastDateFormat—A replacement for SimpleDateFormat that is fast and thread-safe ☞ DateFormatUtils—A formatting class for dates ☞ StopWatch—A duration timer Iverson_appA.qxd 1/17/05 2:37 PM Page 312 312 Lang Reference Appendix A Class Summary ☞ DateFormatUtils Date and time formatting utilites and constants. ☞ DateUtils A suite of utilities surrounding the use of the Calendar and Date object. ☞ FastDateFormat FastDateFormat is a fast and thread-safe version of SimpleDateFormat. ☞ StopWatch StopWatch provides a convenient API for timings. org.apache.commons.lang.time.DateFormatUtils Date and time formatting utilites and constants. Formatting is performed using the FastDateFormat class. public static final FastDateFormat ISO_DATETIME_FORMAT ISO8601 formatter for date-time witout time zone. The format used is yyyy-MM- dd'T'HH:mm:ss. public static final FastDateFormat ISO_DATETIME_TIME_ZONE_FORMAT ISO8601 formatter for date-time with time zone. The format used is yyyy-MM- dd'T'HH:mm:ssZZ. public static final FastDateFormat ISO_DATE_FORMAT ISO8601 formatter for date without time zone. The format used is yyyy-MM-dd. public static final FastDateFormat ISO_DATE_TIME_ZONE_FORMAT ISO8601-like formatter for date with time zone. The format used is yyyy-MM- ddZZ. This pattern does not comply with the formal ISO8601 specification as the standard does not allow a time zone without a time. public static final FastDateFormat ISO_TIME_FORMAT ISO8601 formatter for time without time zone. The format used is 'T'HH:mm:ss. public static final FastDateFormat ISO_TIME_TIME_ZONE_FORMAT ISO8601 formatter for time with time zone. The format used is 'T'HH:mm:ssZZ. public static final FastDateFormat ISO_TIME_NO_T_FORMAT ISO8601-like formatter for time without time zone. The format used is HH:mm:ss. This pattern does not comply with the formal ISO8601 specification as the standard requires the 'T' prefix for times. public static final FastDateFormat ISO_TIME_NO_T_TIME_ZONE_FORMAT Iverson_appA.qxd 1/17/05 2:37 PM Page 313 org.apache.commons.lang.time 313 ISO8601-like formatter for time with time zone. The format used is HH:mm:ssZZ. This pattern does not comply with the formal ISO8601 specifica- tion as the standard requires the 'T' prefix for times. public static final FastDateFormat SMTP_DATETIME_FORMAT SMTP (and probably other) date headers. The format used is EEE, dd MMM yyyy HH:mm:ss Z in U.S. locale. Constructor Detail public DateFormatUtils() DateFormatUtils instances should NOT be constructed in standard program- ming. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.lang.String formatUTC(long millis, java.lang.String pattern) Format a date/time into a specific pattern using the UTC time zone. Parameters: millis—the date to format expressed in milliseconds pattern—the pattern to use to format the date Returns: the formatted date public static java.lang.String formatUTC(java.util.Date date, java.lang.String pattern) Format a date/time into a specific pattern using the UTC time zone. Parameters: date—the date to format pattern—the pattern to use to format the date Returns: the formatted date public static java.lang.String formatUTC(long millis, java.lang.String pattern, java.util.Locale locale) Format a date/time into a specific pattern using the UTC time zone. Parameters: millis—the date to format expressed in milliseconds pattern—the pattern to use to format the date locale—the locale to use, may be null Returns: the formatted date public static java.lang.String formatUTC(java.util.Date date, java.lang.String pattern, java.util.Locale locale) Iverson_appA.qxd 1/17/05 2:37 PM Page 314 314 Lang Reference Appendix A Format a date/time into a specific pattern using the UTC time zone. Parameters: date—the date to format pattern—the pattern to use to format the date locale—the locale to use, may be null Returns: the formatted date public static java.lang.String format(long millis, java.lang.String pattern) Format a date/time into a specific pattern. Parameters: millis—the date to format expressed in milliseconds pattern—the pattern to use to format the date Returns: the formatted date public static java.lang.String format(java.util.Date date, java.lang.String pattern) Format a date/time into a specific pattern. Parameters: date—the date to format pattern—the pattern to use to format the date Returns: the formatted date public static java.lang.String format(long millis, java.lang.String pattern, java.util.TimeZone timeZone) Format a date/time into a specific pattern in a time zone. Parameters: millis—the time expressed in milliseconds pattern—the pattern to use to format the date timeZone—the time zone to use, may be null Returns: the formatted date public static java.lang.String format(java.util.Date date, java.lang.String pattern, java.util.TimeZone timeZone) Format a date/time into a specific pattern in a time zone. Parameters: date—the date to format pattern—the pattern to use to format the date timeZone—the time zone to use, may be null Returns: the formatted date public static java.lang.String format(long millis, java.lang.String pattern, java.util.Locale locale) Format a date/time into a specific pattern in a locale. Parameters: millis—the date to format expressed in milliseconds pattern—the pattern to use to format the date Iverson_appA.qxd 1/17/05 2:37 PM Page 315 org.apache.commons.lang.time 315 locale—the locale to use, may be null Returns: the formatted date public static java.lang.String format(java.util.Date date, java.lang.String pattern, java.util.Locale locale) Format a date/time into a specific pattern in a locale. Parameters: date—the date to format pattern—the pattern to use to format the date locale—the locale to use, may be null Returns: the formatted date public static java.lang.String format(long millis, java.lang.String pattern, java.util.TimeZone timeZone, java.util.Locale locale) Format a date/time into a specific pattern in a time zone and locale. Parameters: millis—the date to format expressed in milliseconds pattern—the pattern to use to format the date timeZone—the time zone to use, may be null locale—the locale to use, may be null Returns: the formatted date public static java.lang.String format(java.util.Date date, java.lang.String pattern, java.util.TimeZone timeZone, java.util.Locale locale) Format a date/time into a specific pattern in a time zone and locale. Parameters: date—the date to format pattern—the pattern to use to format the date timeZone—the time zone to use, may be null locale—the locale to use, may be null Returns: the formatted date org.apache.commons.lang.time.DateUtils A suite of utilities surrounding the use of the Calendar and Date object. Field Detail public static final java.util.TimeZone UTC_TIME_ZONE The UTC time zone (often referred to as GMT). public static final int MILLIS_IN_SECOND Number of milliseconds in a standard second. public static final int MILLIS_IN_MINUTE Iverson_appA.qxd 1/17/05 2:37 PM Page 316 316 Lang Reference Appendix A Number of milliseconds in a standard minute. public static final int MILLIS_IN_HOUR Number of milliseconds in a standard hour. public static final int MILLIS_IN_DAY Number of milliseconds in a standard day. public static final int SEMI_MONTH This is half a month, so this represents whether a date is in the top or bottom half of the month. public static final int RANGE_WEEK_SUNDAY A week range, starting on Sunday. public static final int RANGE_WEEK_MONDAY A week range, starting on Monday. public static final int RANGE_WEEK_RELATIVE A week range, starting on the day focused. public static final int RANGE_WEEK_CENTER A week range, centered around the day focused. public static final int RANGE_MONTH_SUNDAY A month range, the week starting on Sunday. public static final int RANGE_MONTH_MONDAY A month range, the week starting on Monday. Constructor Detail public DateUtils() DateUtils instances should NOT be constructed in standard programming. Instead, the class should be used as DateUtils.parse(str);. This constructor is public to permit tools that require a JavaBean instance to operate. Method Detail public static java.util.Date round(java.util.Date date, int field) Iverson_appA.qxd 1/17/05 2:37 PM Page 317 org.apache.commons.lang.time 317 Round this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April 2002 0:00:00.000. Parameters: date—the date to work with field—the field from Calendar or SEMI_MONTH Returns: the rounded date Throws: java.lang.IllegalArgumentException—if the date is null public static java.util.Calendar round(java.util.Calendar date, int field) Round this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April 2002 0:00:00.000. Parameters: date—the date to work with field—the field from Calendar or SEMI_MONTH Returns: the rounded date (a different object) Throws: java.lang.IllegalArgumentException—if the date is null public static java.util.Date round(java.lang.Object date, int field) Round this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April 2002 0:00:00.000. Parameters: date—the date to work with, either Date or Calendar field—the field from Calendar or SEMI_MONTH Returns: the rounded date Throws: java.lang.IllegalArgumentException—if the date is null java.lang.ClassCastException—if the object type is not a Date or Calendar public static java.util.Date truncate(java.util.Date date, int field) Truncate this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002 0:00:00.000. Parameters: date—the date to work with field—the field from Calendar or SEMI_MONTH Returns: the rounded date Throws: java.lang.IllegalArgumentException—if the date is null public static java.util.Calendar truncate(java.util.Calendar date, int field) Iverson_appA.qxd 1/17/05 2:37 PM Page 318 318 Lang Reference Appendix A Truncate this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002 0:00:00.000. Parameters: date—the date to work with field—the field from Calendar or SEMI_MONTH Returns: the rounded date (a different object) Throws: java.lang.IllegalArgumentException—if the date is null public static java.util.Date truncate(java.lang.Object date, int field) Truncate this date, leaving the field specified as the most significant field. For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002 0:00:00.000. Parameters: date—the date to work with, either Date or Calendar field—the field from Calendar or SEMI_MONTH Returns: the rounded date Throws: java.lang.IllegalArgumentException—if the date is null java.lang.ClassCastException—if the object type is not a Date or Calendar public static java.util.Iterator iterator(java.util.Date focus, int rangeStyle) This constructs an Iterator that will start and stop over a date range based on the focused date and the range style. For instance, passing Thursday, July 4, 2002 and a RANGE_MONTH_SUNDAY will return an Iterator that starts with Sunday, June 30, 2002 and ends with Saturday, August 3, 2002. Parameters: focus—the date to work with rangeStyle—the style constant to use. Must be one of the range styles listed for the iterator(Calendar, int) method. Returns: the date iterator Throws: java.lang.IllegalArgumentException—if the date is null or if the rangeStyle is not public static java.util.Iterator iterator(java.util.Calendar focus, int rangeStyle) This constructs an Iterator that will start and stop over a date range based on the focused date and the range style. For instance, passing Thursday, July 4, 2002 and a RANGE_MONTH_SUNDAY will return an Iterator that starts with Sunday, June 30, 2002 and ends with Saturday, August 3, 2002. Parameters: focus—the date to work with rangeStyle—the style constant to use. Must be one of RANGE_MONTH_SUNDAY, RANGE_MONTH_MONDAY, RANGE_WEEK_SUNDAY, RANGE_WEEK_MONDAY, RANGE_WEEK_RELATIVE, RANGE_WEEK_CENTER Iverson_appA.qxd 1/17/05 2:37 PM Page 319 org.apache.commons.lang.time 319 Returns: the date iterator Throws: java.lang.IllegalArgumentException—if the date is null public static java.util.Iterator iterator(java.lang.Object focus, int rangeStyle) This constructs an Iterator that will start and stop over a date range based on the focused date and the range style. For instance, passing Thursday, July 4, 2002 and a RANGE_MONTH_SUNDAY will return an Iterator that starts with Sunday, June 30, 2002 and ends with Saturday, August 3, 2002. Parameters: focus—the date to work with, either Date or Calendar rangeStyle—the style constant to use. Must be one of the range styles listed for the iterator(Calendar, int) method. Returns: the date iterator Throws: java.lang.IllegalArgumentException—if the date is null java.lang.ClassCastException—if the object type is not a Date or Calendar org.apache.commons.lang.time.FastDateFormat public class FastDateFormat extends java.text.Format FastDateFormat is a fast and thread-safe version of SimpleDateFormat. This class can be used as a direct replacement to SimpleDateFormat in most formatting situations. This class is especially useful in multi-threaded server environments. SimpleDateFormat is not thread-safe in any JDK ver- sion, nor will it be as Sun has closed the bug/RFE. Only formatting is supported, but all patterns are compatible with SimpleDateFormat (except time zones—see below). Java 1.4 introduced a new pattern letter, 'Z', to represent time zones in RFC822 format (e.g., +0800 or -1100). This pattern letter can be used here (on all JDK versions). In addition, the pattern 'ZZ' has been made to represent ISO8601 full format time zones (e.g., +08:00 or -11:00). This introduces a minor incompatability with Java 1.4, but at a gain of useful functionality. Nested Class Summary Nested classes inherited from class java.text.Format java.text.Format.Field Methods inherited from class java.text.Format clone, format, formatToCharacterIterator, parseObject Field Detail public static final int FULL FULL locale dependent date or time style. public static final int LONG Iverson_appA.qxd 1/17/05 2:37 PM Page 320 320 Lang Reference Appendix A LONG locale dependent date or time style. public static final int MEDIUM MEDIUM locale dependent date or time style. public static final int SHORT SHORT locale dependent date or time style. Method Detail public static FastDateFormat getInstance() Gets a formatter instance using the default pattern in the default locale. Returns: a date/time formatter public static FastDateFormat getInstance(java.lang.String pattern) Gets a formatter instance using the specified pattern in the default locale. Parameters: pattern—SimpleDateFormat compatible pattern Returns: a pattern based date/time formatter Throws: java.lang.IllegalArgumentException—if pattern is invalid public static FastDateFormat getInstance(java.lang.String pattern, java.util.TimeZone timeZone) Gets a formatter instance using the specified pattern and time zone. Parameters: pattern—SimpleDateFormat compatible pattern timeZone—optional time zone, overrides time zone of formatted date Returns: a pattern based date/time formatter Throws: java.lang.IllegalArgumentException—if pattern is invalid public static FastDateFormat getInstance(java.lang.String pattern, java.util.Locale locale) Gets a formatter instance using the specified pattern and locale. Parameters: pattern—SimpleDateFormat compatible pattern locale—optional locale, overrides system locale Returns: a pattern based date/time formatter Throws: java.lang.IllegalArgumentException—if pattern is invalid public static FastDateFormat getInstance(java.lang.String pattern, java.util.TimeZone timeZone, java.util.Locale locale) Gets a formatter instance using the specified pattern, time zone and locale. Parameters: pattern—SimpleDateFormat compatible pattern timeZone—optional time zone, overrides time zone of formatted date locale—optional locale, overrides system locale Iverson_appA.qxd 1/17/05 2:37 PM Page 321 org.apache.commons.lang.time 321 Returns: a pattern based date/time formatter Throws: java.lang.IllegalArgumentException—if pattern is invalid or null public static FastDateFormat getDateInstance(int style, java.util.TimeZone timeZone, java.util.Locale locale) Gets a date formatter instance using the specified style, time zone and locale. Parameters: style—date style: FULL, LONG, MEDIUM, or SHORT timeZone—optional time zone, overrides time zone of formatted date locale—optional locale, overrides system locale Returns: a localized standard date formatter Throws: java.lang.IllegalArgumentException—if the Locale has no date pattern defined public static FastDateFormat getTimeInstance(int style, java.util.TimeZone timeZone, java.util.Locale locale) Gets a time formatter instance using the specified style, time zone and locale. Parameters: style—time style: FULL, LONG, MEDIUM, or SHORT timeZone—optional time zone, overrides time zone of formatted time locale—optional locale, overrides system locale Returns: a localized standard time formatter Throws: java.lang.IllegalArgumentException—if the Locale has no time pattern defined public static FastDateFormat getDateTimeInstance(int dateStyle, int timeStyle, java.util.TimeZone timeZone, java.util.Locale locale) Gets a date/time formatter instance using the specified style, time zone and locale. Parameters: dateStyle—date style: FULL, LONG, MEDIUM, or SHORT timeStyle—time style: FULL, LONG, MEDIUM, or SHORT timeZone—optional time zone, overrides time zone of formatted date locale—optional locale, overrides system locale Returns: a localized standard date/time formatter Throws: java.lang.IllegalArgumentException—if the Locale has no date/time pattern defined public java.lang.StringBuffer format(java.lang.Object obj, java.lang.StringBuffer toAppendTo, java.text.FieldPosition pos) Format either a Date or a Calendar object. Parameters: obj—the object to format toAppendTo—the buffer to append to pos—the position—ignored Returns: the buffer passed in public java.lang.String format(java.util.Date date) Iverson_appA.qxd 1/17/05 2:37 PM Page 322 322 Lang Reference Appendix A Formats a Date object. Parameters: date—the date to format Returns: the formatted string public java.lang.String format(java.util.Calendar calendar) Formats a Calendar object. Parameters: calendar—the calendar to format Returns: the formatted string public java.lang.StringBuffer format(java.util.Date date, java.lang.StringBuffer buf) Formats a Date object into the supplied StringBuffer. Parameters: date—the date to format buf—the buffer to format into Returns: the specified string buffer public java.lang.StringBuffer format(java.util.Calendar calendar, java.lang.StringBuffer buf) Formats a Calendar object into the supplied StringBuffer. Parameters: calendar—the calendar to format buf—the buffer to format into Returns: the specified string buffer public java.lang.Object parseObject(java.lang.String source, java.text.ParsePosition pos) Parsing not supported. Parameters: source—the string to parse pos—the parsing position Returns: null as not supported public java.lang.String getPattern() Gets the pattern used by this formatter. Returns: the pattern, SimpleDateFormat compatible public java.util.TimeZone getTimeZone() Gets the time zone used by this formatter. This zone is always used for Date formatting. If a Calendar is passed in to be formatted, the time zone on that may be used depending on getTimeZoneOverridesCalendar(). Returns: the time zone public boolean getTimeZoneOverridesCalendar() Iverson_appA.qxd 1/17/05 2:37 PM Page 323 org.apache.commons.lang.time 323 Returns true if the time zone of the calendar overrides the time zone of the formatter. Returns: true if time zone of formatter overridden for calendars public java.util.Locale getLocale() Gets the locale used by this formatter. Returns: the locale public int getMaxLengthEstimate() Gets an estimate for the maximum string length that the formatter will produce. The actual formatted length will almost always be less than or equal to this amount. Returns: the maximum formatted length public boolean equals(java.lang.Object obj) Compare two objects for equality. Parameters: obj—the object to compare to Returns: true if equal public int hashCode() A suitable hashcode. Returns: a hashcode compatable with equals public java.lang.String toString() Gets a debugging string version of this formatter. Returns: a debugging string org.apache.commons.lang.time.StopWatch StopWatch provides a convenient API for timings. The methods do not protect against inappropriate calls. Thus you can call stop before start, resume before suspend, or unsplit before split. The results are indeterminate in these cases. To start the watch, call start(). At this point you can: ☞ split() the watch to get the time whilst the watch continues in the back- ground. unsplit() will remove the effect of the split. At this point, these three options are available again. ☞ suspend() the watch to pause it. resume() allows the watch to continue. Any time between the suspend and resume will not be counted in the total. At this point, these three options are available again. ☞ stop() the watch to complete the timing session. Iverson_appA.qxd 1/17/05 2:37 PM Page 324 324 Lang Reference Appendix A It is intended that the output methods toString() and getTime() should only be called after stop, split or suspend, however a suitable result will be returned at other points. Constructor Detail public StopWatch() Method Detail public void start() Start the stopwatch. This method starts a new timing session, clearing any previous values. public void stop() Stop the stopwatch. This method ends a new timing session, allowing the time to be retrieved. public void reset() Reset the stopwatch. This method clears the internal values to allow the object to be reused. public void split() Split the time. This method sets the stop time of the watch to allow a time to be extracted. The start time is unaffected, enabling unsplit() to contine the timing from the original start point. public void unsplit() Remove a split. This method clears the stop time. The start time is unaffected, enabling timing from the original start point to continue. public void suspend() Suspend the stopwatch for later resumption. This method suspends the watch until it is resumed. The watch will not include time between the suspend and resume calls in the total time. public void resume() Resume the stopwatch after a suspend. This method resumes the watch after it was suspended. The watch will not include time between the suspend and resume calls in the total time. public long getTime() Iverson_appA.qxd 1/17/05 2:37 PM Page 325 org.apache.commons.lang.time 325 Get the time on the stopwatch. This is either the time between start and latest split, between start and stop, or the time between the start and the moment this method is called. Returns: the time in milliseconds public java.lang.String toString() Gets a summary of the time that the stopwatch recorded as a string. The format used is ISO8601-like, hours:minutes:seconds.milliseconds. Returns: the time as a String Iverson_appA.qxd 1/17/05 2:37 PM Page 326 Iverson_appB.qxd 1/17/05 2:44 PM Page 327 A P P E N D I X B Apache License, Version 2.0 Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for use, repro- duction, and distribution as defined by Sections 1 through 9 of this document. "Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. "Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. 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Iverson_Index.qxd 1/18/05 11:20 AM Page 331 I N D E X Symbols == (equality) operation, 153 A Apache Jakarta Commons project configuration under Eclipse, 5–9 license for, 4 obtaining and installing, 4 overview, 1 Apache Software Foundation license, 4 applications BeanUtils example application, 94–103 ClassPathTool utility (CLI package), 179–184 complete source code, 186–191 running command line, 184–185 custom DataSources (DBCP package), 81–86 FileUpload example, 16–26 FTP example (Net package), 48–54 JXPath object graph example hierarchy exploration, 110–113 setup, 107–110 legacy JDBC driver example (DBCP package), 86–88 Logging package example, 120–122 output, 122–125 NNTP example (Net package), 54–66 object factory example (Pool package), 74–75 Swing client example (HttpClient package), 37–43 thread pool example (Pool package), 69–74 worker thread example (Pool package), 75–77 B Bag class (Collections package), 140–142 Base64 encoding (Codec package), 170–171 BasePoolableObjectFactory class (Pool package), 69 BeanMap class (Collections package), 142–144 BeanUtils package, 92–93 classes, 93 FormBean application example, 94–103 project ideas, 103 Betwixt package, 193 BidiMap class (Collections package), 144–145, 148 BitField class (Lang package), 128, 201, 225–228 BlockingBuffer class (Collections package), 145 BooleanUtils class (Lang package), 128–129, 201, 228–234 Bounded class (Collections package), 145–147 BSD R commands, 46 Buffer class (Collections package), 147 Builder package (Lang package), 135 C Cache package, 196 Chain package, 193 character encoding (Codec package), 166–170 CharRange class (Lang package), 129, 201, 234–236 CharSet class (Lang package), 129, 201, 236–238 CharSetUtils class (Lang package), 129, 201, 238–241 ArrayUtils class (Lang package), 128, CircularFifoBuffer class (Collections 201–225 ASCII, 166 Attributes package, 196 package), 147 classes. See also interfaces ArrayUtils (Lang package), 128, 201–225 Bag (Collections package), 140–142 331 Iverson_Index.qxd 1/18/05 11:20 AM Page 332 332 Index BeanMap (Collections package), 142–144 BeanUtils package, 93 BidiMap (Collections package), 144–145, 148 BitField (Lang package), 128, 201, 225–228 BlockingBuffer (Collections package), 145 BooleanUtils (Lang package), 128–129, 201, 228–234 Bounded (Collections package), 145–147 Buffer (Collections package), 147 Builder package, 135 CharRange (Lang package), 129, 201, 234–236 CharSet (Lang package), 129, 201, 236–238 Hash (Collections package), 153 HttpClient package, 29, 32–37 Identity (Collections package), 153 IOUtils (IO package), 194 Lazy (Collections package), 154 Linked (Collections package), 154 List (Collections package), 154–156 LRUMap (Collections package), 156 Map (Collections package), 156 Math package, 136–137 Multi (Collections package), 158 Net package, 46 NewsgroupInfo (Net package), 57 NNTPConnection (Net package), 59 NodeCachingLinkedList (Collections package), 158 CharSetUtils (Lang package), 129, 201, ObjectGraph (Collections package), 238–241 158–159 CircularFifoBuffer (Collections ObjectUtils (Lang package), 130, 202, package), 147 245–247 ClassUtils (Lang package), 130, 202, ObjectUtils.Null (Lang package), 130, 241–244 Closure (Collections package), 147–149 Codec package, 166 CollatingIterator (Collections package), 150 Collections package, 140 Comparator (Collections package), 150–151 Composite (Collections package), 151 CopyUtils (IO package), 194 CursorableLinkedList (Collections package), 151–152 DataSource (DBCP package), 81–86 DateFormatUtils (Time package), 312–315 DateUtils (Time package), 315–319 DiskFileUpload (FileUpload package), 13–15 EnumUtils (Enum package), 136 Factory (Collections package), 152 Fast (Collections package), 152 FastDateFormat (Time package), 319–323 Fifo (Collections package), 152 FileUploadHelper (FileUpload application example), 20–23 FileUtils (IO package), 194 FixedSize (Collections package), 152 Flat3Map (Collections package), 153 FormBean (BeanUtils package), 94–103 ftp package classes (Net package), 46 FTPConnection (Net package), 49–50 Functor (Collections package), 153 202, 247 Ordered (Collections package), 159 Person (JXPath package), 105–108 Pool package, 68–69 PoolingDriver (DBCP package), 79, 86 Predicate (Collections package), 160 RandomStringUtils (Lang package), 130–131, 202, 247–250 ReferenceMap (Collections package), 160 SerializationUtils (Lang package), 131, 202, 250–252 Set (Collections package), 160 Singleton (Collections package), 160 StaticBucketMap (Collections package), 162 StopWatch (Time package), 323–325 StringEscapeUtils (Lang package), 131, 202, 252–256 StringUtils (Lang package), 132–133, 202, 256–295 Synchronized (Collections package), 162 SystemUtils (Lang package), 134, 202, 295–303 Time package, 137, 311–312 Transformer (Collections package), 162 Typed (Collections package), 163 Unmodifiable (Collections package), 163 Validate (Lang package), 134, 202, 303–309 WordUtils (Lang package), 134–135, 202, 309–311 WorkerThreadFactory (Pool package), 69 Iverson_Index.qxd 1/18/05 11:20 AM Page 333 Index 333 ClassPathTool utility, 179 building command-line interface with CLI package, 181–184 complete source code, 186–191 running command line, 184–185 ClassUtils class (Lang package), 130, 202, 241–244 Clazz package, 196 CLI package, 179 ClassPathTool utility example, 179–184 complete source code, 186–191 running command line, 184–185 project ideas, 191 clients. See HttpClient package Closure class (Collections package), 147–149 Codec package, 165 Base64 encoding, 170–171 character encoding, 166–170 classes, 166 hash generation, 173–175 phonetic analysis, 175–176 project ideas, 177 URL parameter encoding, 171–172 CollatingIterator class (Collections package), 150 Collections package, 139–140 Bag class, 140–142 BeanMap class, 142–144 BidiMap class, 144–145, 148 BlockingBuffer class, 145 Bounded class, 145–147 Buffer class, 147 CircularFifoBuffer class, 147 Closure class, 147–149 CollatingIterator class, 150 Comparator class, 150–151 Composite class, 151 CursorableLinkedList class, 151–152 Factory class, 152 Fast class, 152 Fifo class, 152 FixedSize class, 152 Flat3Map class, 153 Functor class, 153 Hash class, 153 Identity class, 153 Lazy class, 154 Linked class, 154 List class, 154–156 LRUMap class, 156 Map class, 156 Multi class, 158 NodeCachingLinkedList class, 158 ObjectGraph class, 158–159 Ordered class, 159 Predicate class, 160 project ideas, 164 ReferenceMap class, 160 Set class, 160 Singleton class, 160 StaticBucketMap class, 162 Synchronized class, 162 Transformer class, 162 Typed class, 163 Unmodifiable class, 163 command-line interface. See CLI package Commons project. See Apache Jakarta Commons project Comparator class (Collections package), 150–151 CompareToBuilder class (Builder package), 135 components of Commons project. See names of specific components Composite class (Collections package), 151 Compress package, 196 compression. See Codec package configuration of Apache Jakarta Commons packages under Eclipse, 5–9 Configuration package, 193 connection pooling. See DBCP package; Pool package constructors ArrayUtils class (Lang package), 204 BitField class (Lang package), 225 BooleanUtils class (Lang package), 228 CharRange class (Lang package), 234–235 CharSetUtils class (Lang package), 238 ClassUtils class (Lang package), 241 DateFormatUtils class (Time package), 313 DateUtils class (Time package), 316 ObjectUtils class (Lang package), 245 RandomStringUtils class (Lang package), 247 SerializationUtils class (Lang package), 251 StopWatch class (Time package), 324 StringEscapeUtils class (Lang package), 252 StringUtils class (Lang package), 257 SystemUtils class (Lang package), 303 Validate class (Lang package), 303 WordUtils class (Lang package), 309 content types, 34 Convert package, 196 Converter package (BeanUtils package), 93, 101 Iverson_Index.qxd 1/18/05 11:20 AM Page 334 334 Index cookie-based web site example, 31–32 CopyUtils class (IO package), 194 CursorableLinkedList class (Collections package), 151–152 D Daemon package, 193 data types, JXPath package support, 116 Database Connection Pool. See DBCP package DataSource class (DBCP package), 81–86 DateFormatUtils class (Time package), 137, 312–315 DateUtils class (Time package), 137, 315–319 DBCP package, 79–81. See also Pool package custom DataSources, 81–86 legacy JDBC driver application example, 86–88 project ideas, 89 DbUtils package, 194 debugging information, printing. See Logging package Digester package, 194 directory naming conventions, 5, 24 Discovery package, 194 DiskFileUpload class (FileUpload package), 13–15 DoubleRange class (Math package), 136 downloading files. See HttpClient package DynaBean class (BeanUtils package), 93 DynaClass class (BeanUtils package), 93 E echo() method, 140 Eclipse, configuration of Apache Jakarta Commons packages, 5–9 EL package, 194 Email package, 197 email protocols, JavaMail support for, 45 encoding. See Codec package Enum package (Lang package), 136 EnumUtils class (Enum package), 136 equality (==) operation, 153 EqualsBuilder class (Builder package), 135 escaping strings, StringEscapeUtils class (Lang package), 131, 202, 252–256 Events package, 197 Exception package (Lang package), 136 Expression Language, 194–195 extensions, JXPath package, 115–116 F Factory class (Collections package), 152 family tree example. See object graphs Fast class (Collections package), 152 FastDateFormat class (Time package), 137, 319–323 Feedparser package, 197 Fifo class (Collections package), 152 FileItem interface (FileUpload package), 15 FileUpload package, 11 application example, 16–26 DiskFileUpload class, 13–15 FileItem interface, 15 limitations and security issues, 26–27 project ideas, 27 user interface, 13 FileUploadHelper class (FileUpload application example), 20–23 FileUtils class (IO package), 194 Finger, 45 FixedSize class (Collections package), 152 Flat3Map class (Collections package), 153 FloatRange class (Math package), 136 FormBean class (BeanUtils package), 94–103 Fraction class (Math package), 136–137 FTP, 45, 48–54 ftp package (Net package) application example, 48–54 classes, 46 FTPClient class (Net package), 46 FTPConnection class (Net package), 49–50 functions, Functor package, 197 Functor class (Collections package), 153 Functor package, 197 G–H GenericObjectPool class (Pool package), 69 GET method, 34 HttpClient package, 31 Swing client example (HttpClient package), 39–40 graphs of objects. See object graphs Hash class (Collections package), 153 hash generation, Codec package, 173–175 HashCodeBuilder class (Builder package), 135 Hibernate, 92 hierarchy exploration, JXPath object graph example, 110–113 HttpClient package classes, 29, 32–37 methods, 34 MIME types, 34 Iverson_Index.qxd 1/18/05 11:20 AM Page 335 Index 335 project ideas, 44 server redirects, 31 Swing client example, 37–43 HttpMethod interface (HttpClient package), 34 HttpState class (HttpClient package), 34 HttpUrlMethod interface (HttpClient package), 34 I Id package, 197 Identity class (Collections package), 153 index.jsp page (FileUpload application example), 18 interfaces. See also classes FileItem (FileUpload package), 15 HttpMethod (HttpClient package), 34 HttpUrlMethod (HttpClient package), 34 Pool package, 69 PoolableObjectFactory (Pool package), 74 Internet protocols JavaMail support for, 45 Net package support for, 45–46 IntRange class (Math package), 136 IO package, 194 IOUtils class (IO package), 194 J Jakarta JAR Archive Repository, 197 Jakarta projects, examples of, 4 James (Java-based mail and NNTP server), 66 Java, mapping XML to, 194 JavaBeans specification, 91–92 BeanUtils package, 92–103 mapping JavaBeans to XML documents, 193 JavaMail, Internet protocols supported, 45 JDBC connections, DBCP package, 79–81 JDBC driver application example (DBCP package), 86–88 Jelly package, 195 Jexl package, 195 JJar package, 197 JSP, retrieving data, 11–13 JVMRandom class (Math package), 137 JXPath package, 105–106 data types supported, 116 hierarchy exploration, 110–113 object graph setup, 107–110 performance, 116 project ideas, 117 XPath syntax, 113–116 K–L KeyedObjectPool class (Pool package), 69 Lang package, 127 ArrayUtils class, 128, 201–225 BitField class, 128, 201, 225–228 BooleanUtils class, 128–129, 201, 228–234 Builder package, 135 CharRange class, 129, 201, 234–236 CharSet class, 129, 201, 236–238 CharSetUtils class, 129, 201, 238–241 ClassUtils class, 130, 202, 241–244 Enum package, 136 Exception package, 136 Math package, 136–137 ObjectUtils class, 130, 202, 245–247 ObjectUtils.Null class, 130, 202, 247 packages in, 127 project ideas, 138 RandomStringUtils class, 130–131, 202, 247–250 SerializationUtils class, 131, 202, 250–252 StringEscapeUtils class, 131, 202, 252–256 StringUtils class, 132–133, 202, 256–295 SystemUtils class, 134, 202, 295–303 Time package, 137, 311–312 DateFormatUtils class, 312–315 DateUtils class, 315–319 FastDateFormat class, 319–323 StopWatch class, 323–325 Validate class, 134, 202, 303–309 WordUtils class, 134–135, 202, 309–311 Latka package, 195 Launcher package, 195 Lazy class (Collections package), 154 legacy JDBC driver application example (DBCP package), 86–88 libraries. See names of specific libraries licenses, Apache Software Foundation license, 4 limitations, FileUpload package, 26–27 Linked class (Collections package), 154 List class (Collections package), 154–156 Log4j toolkit, 119 Logging package, 119 application example, 120–122 levels of messages, 119–120 output examples, 122–125 project ideas, 125 LongRange class (Math package), 136 LRUMap class (Collections package), 156 Iverson_Index.qxd 1/18/05 11:20 AM Page 336 336 Index M Map class (Collections package), 156 Mapper package, 197 Math package (Lang package), 136–137, 195 MD5 hash generation, Codec package, 173–175 Messenger package, 198 Metaphone phonetic analysis, 175 methods ArrayUtils class (Lang package), 204–225 BitField class (Lang package), 225–228 BooleanUtils class (Lang package), 228–234 CharRange class (Lang package), 235–236 CharSet class (Lang package), 237–238 CharSetUtils class (Lang package), 238–241 ClassUtils class (Lang package), 241–244 DateFormatUtils class (Time package), 313–315 DateUtils class (Time package), 317–319 FastDateFormat class (Time package), 320–323 HttpClient package, 34 ObjectUtils class (Lang package), 245–247 RandomStringUtils class (Lang package), 248–250 SerializationUtils class (Lang package), 251–252 StopWatch class (Time package), 324–325 StringEscapeUtils class (Lang package), 252–256 StringUtils class (Lang package), 257–295 SystemUtils class (Lang package), 303 Validate class (Lang package), 304–309 WordUtils class (Lang package), 309–311 MIME types, 34 Modeler package, 195 Multi class (Collections package), 158 N naming conventions directories, 5 uploaded files, 24 Net package ftp package application example, 48–54 classes, 46 Internet protocols supported, 45–46 nntp package, application example, 54–66 origins of, 47 packages included, list of, 46 project ideas, 66 NetComponents, 47 NewsgroupInfo class (Net package), 57 newsgroups, hierarchy of, 55 NNTP, 45 Net package application example, 54–66 newsgroup hierarchy, 55 nntp package (Net package), application example, 54–66 NNTPConnection class (Net package), 59 NodeCachingLinkedList class (Collections package), 158 null values ArrayUtils class (Lang package), 203 ObjectUtils.Null class (Lang package), 130, 202, 247 StringUtils class (Lang package), 132–133, 202, 256–295 NumberRange class (Math package), 136 NumberUtils class (Math package), 137 O object factory application, Pool package example, 74–75 object graphs, JXPath package, 105–106 data types supported, 116 hierarchy exploration, 110–113 object graph setup, 107–110 performance, 116 XPath syntax, 113–116 ObjectGraph class (Collections package), 158–159 ObjectPool class (Pool package), 69 ObjectPoolFactory class (Pool package), 69 ObjectUtils class (Lang package), 130, 202, 245–247 ObjectUtils.Null class (Lang package), 130, 202, 247 optimizing object creation, avoiding preoptimization, 67 Ordered class (Collections package), 159 output echo() method, 140 Logging package application example, 122–125 P packages. See Apache Jakarta Commons project; names of specific packages performance JXPath package, 116 threads, impact of, 13 Person class (JXPath package), 105–108 Iverson_Index.qxd 1/18/05 11:20 AM Page 337 Index 337 phonetic analysis, Codec package, 175–176 Pool package, 67. See also DBCP package classes, 68–69 object factory example, 74–75 project ideas, 77 thread pool example, 69, 71–74 worker thread example, 75–77 PoolableObjectFactory interface (Pool package), 69, 74 PoolingDriver class (DBCP package), 79, 86 POST method, 34 Swing client example (HttpClient package), 40–41 Predicate class (Collections package), 160 preoptimization, avoiding, 67 Primitives package, 195 printing debugging information. See Logging package project ideas BeanUtils package, 103 CLI package, 191 Codec package, 177 Collections package, 164 DBCP package, 89 FileUpload package, 27 HttpClient package, 44 JXPath package, 117 Lang package, 138 Logging package, 125 Net package, 66 Pool package, 77 proper components list of, 2–3 versus sandbox components, 2 proper projects, web site for information, 193 protocols. See Internet protocols Q–R RandomStringUtils class (Lang package), 130–131, 202, 247–250 RandomUtils class (Math package), 137 Range class (Math package), 136 redirects, HttpClient package, 31 ReferenceMap class (Collections package), 160 ReflectionToStringBuilder class (Builder package), 135 Resources package, 198 retrieving S sandbox components versus proper components, 2 sandbox projects, 196 Scaffold package, 198 Secure Hash Algorithm. See SHA security issues, FileUpload package, 26–27 SerializationUtils class (Lang package), 131, 202, 250–252 server redirects, HttpClient package, 31 servlets performance impact of threads, 13 retrieving data, 11–13 Set class (Collections package), 160 SHA (Secure Hash Algorithm), 173 hash generation, Codec package, 173–175 Singleton class (Collections package), 160 SoftReferenceObjectPool class (Pool package), 69 SoundEx phonetic analysis, 175 spell-checking (phonetic analysis), 175 SQL package, 198 StackObjectPool class (Pool package), 69 StandardToStringStyle class (Builder package), 135 StaticBucketMap class (Collections package), 162 StopWatch class (Time package), 137, 323–325 StringEscapeUtils class (Lang package), 131, 202, 252–256 StringUtils class (Lang package), 132–133, 202, 256–295 Swing client HttpClient package example, 37–43 JXPath object graph example, 110–113 Synchronized class (Collections package), 162 SystemUtils class (Lang package), 134, 202, 295–303 T Telnet, 45 TFTP, 45 ThreadPool package, 198 threads performance impact, 13 Pool package application example, 69–77 Swing client example (HttpClient package), 41 ThreadPool package, 198 Time package (Lang package), 137, 311–312 data with JSP or servlets, 11–13 object graph data. See JXPath package DateFormatUtils class, 312–315 DateUtils class, 315–319 Iverson_Index.qxd 1/18/05 11:20 AM Page 338 338 Index FastDateFormat class, 319–323 StopWatch class, 323–325 timeouts, Swing client example (HttpClient package), 41 toolkits for logging, 119 ToStringBuilder class (Builder package), 135 ToStringStyle class (Builder package), 135 Transaction package, 198 Transformer class (Collections package), 162 translations. See Codec package Typed class (Collections package), 163 U Unicode, 168 Unmodifiable class (Collections package), 163 uploading files. See FileUpload package URL parameter encoding, Codec package, 171–172 USENET newsgroup hierarchy, 55 user interface. See also CLI package FileUpload application example, 16–17 FileUpload package, 13 FTP example (Net package), 49 Swing client example (HttpClient package), 37–39 utilities, Lang package. See Lang package V–W Validate class (Lang package), 134, 202, 303–309 Validator package, 196 VFS package, 198 Virtual File System, 198 web pages, cookie-based web site example, 31–32 Whois, 45 WordUtils class (Lang package), 134–135, 202, 309–311 worker thread application, Pool package example, 75–77 WorkerThreadFactory class (Pool package), 69 Workflow package, 199 X–Z XML documents logging output, 123–125 mapping JavaBeans to, 193 mapping to Java, 194 XML-based scripting, 195 XPath syntax, JXPath package, 105–116 data types supported, 116 hierarchy exploration, 110–113 object graph setup, 107–110 performance, 116 Iverson_bm.qxd 1/18/05 2:35 PM Page 339 Iverson_bm.qxd 1/17/05 15:54 Page 340 www.informit.com YOUR GUIDE TO IT REFERENCE Articles Keep your edge with thousands of free articles, in- depth features, interviews, and IT reference recommen- dations – all written by experts you know and trust. 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