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All other trademarks are the property of their respective owners. More Java™ Pitfalls 50 New Time-Saving Solutions and Workarounds More Java™ Pitfalls 50 New Time-Saving Solutions and Workarounds Michael C. Daconta Kevin T. Smith Donald Avondolio W. Clay Richardson Publisher: Joe Wikert Executive Editor: Robert M. Elliott Assistant Developmental Editor: Emilie Herman Managing Editor: Micheline Frederick New Media Editor: Angela Denny Text Design & Composition: Wiley Composition Services This book is printed on acid-free paper. ∞ Copyright 2003 by Michael C. Daconta, Kevin T. Smith, Donald Avondolio, and W. Clay Richardson. All rights reserved. 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Dijkstra who said, “I mean, if 10 years from now, when you are doing something quick and dirty, you suddenly visualize that I am looking over your shoulders and say to yourself, ‘Dijkstra would not have liked this’, well that would be enough immortality for me.” We humbly disagree: 10 years of Dijkstra is just not long enough; may he happily haunt our consciousness for 1010 years. Such an increase is more befitting his stature. Contents Introduction xi Acknowledgments xvii Part One The Client Tier 1 Item 1: When Runtime.exec() Won’t 4 Item 2: NIO Performance and Pitfalls 17 Canonical File Copy 20 Little-Endian Byte Operations 21 Non-Blocking Server IO 26 Item 3: I Prefer Not to Use Properties 34 Item 4: When Information Hiding Hides Too Much 39 Item 5: Avoiding Granularity Pitfalls In java.util.logging 44 Item 6: When Implementations of Standard APIs Collide 53 Item 7: My Assertions are Not Gratuitous! 59 How to Use Assertions 59 Item 8: The Wrong Way to Search a DOM 66 Item 9: The Saving-a-DOM Dilemma 73 Item 10: Mouse Button Portability 80 Item 11: Apache Ant and Lifecycle Management 88 Item 12: JUnit: Unit Testing Made Simple 100 vii viii Contents Item 13: The Failure to Execute 108 Deploying Java Applications 109 The Java Extension Mechanism 110 Sealed Packages 111 Security 112 Item 14: What Do You Collect? 112 Item 15: Avoiding Singleton Pitfalls 117 When Multiple Singletons in Your VM Happen 119 When Singletons are Used as Global Variables, or Become Non-Singletons 120 Item 16: When setSize() Won’t Work 122 Item 17: When Posting to a URL Won’t 126 Connecting via HTTP with the java.net Classes 126 An Alternative Open Source HTTP Client 137 Item 18: Effective String Tokenizing 140 Item 19: JLayered Pane Pitfalls 146 Item 20: When File.renameTo() Won’t 151 Item 21: Use Iteration over Enumeration 157 Item 22: J2ME Performance and Pitfalls 162 Part Two The Web Tier Y 199 L Item 23: Cache, It’s Money F 200 Item 24: JSP Design Errors 208 Request/ResponseM Paradigm 208 Maintaining State 209 JSP the AOld Way 210 JSPE Development with Beans (Model 1 Architecture) 214 TJSP Development in the Model 2 Architecture 220 Item 25: When Servlet HttpSessions Collide 220 Item 26: When Applets Go Bad 227 Item 27: Transactional LDAP—Don’t Make that Commitment 235 Item 28: Problems with Filters 244 Item 29: Some Direction about JSP Reuse and Content Delivery 255 Item 30: Form Validation Using Regular Expressions 261 Team-Fly® Contents ix Item 31: Instance Variables in Servlets 269 Item 32: Design Flaws with Creating Database Connections within Servlets 279 Item 33: Attempting to Use Both Output Mechanisms in Servlets 291 Item 34: The Mysterious File Protocol 297 Item 35: Reading Files from Servlets 302 Web Application Deployment Descriptors 308 Item 36: Too Many Submits 312 Preventing Multiple Submits 314 Handling Multiple Submits 316 Part Three The Enterprise Tier 327 Item 37: J2EE Architecture Considerations 329 Item 38: Design Strategies for Eliminating Network Bottleneck Pitfalls 335 A Scenario 336 General Design Considerations