Struts in Action

Struts in Action Struts in Action Building web applications with the leading Java framework Ted Husted Cedric Dumoulin George Franciscus David Winterfeldt MANNING Greenwich (74° w. long.) struts_00_a.fm Page iv Tuesday, October 29, 2002 11:14 AM For online information and ordering of this and other Manning books, go to www.manning.com. The publisher offers discounts on this book when ordered in quantity. For more information, please contact: Special Sales Department Manning Publications Co. 209 Bruce Park Avenue Fax: (203) 661-9018 Greenwich, CT 06830 email: [email protected] ©2003 by Manning Publications Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in the book, and Manning Publications was aware of a trademark claim, the designations have been printed in initial caps or all caps. Recognizing the importance of preserving what has been written, it is Manning’s policy to have the books they publish printed on acid-free paper, and we exert our best efforts to that end. The following figures were adapted from other Manning books: figure 2.1 from Swing by Matthew Robinson and Pavel Vorobiev (figure 1.3); figures 2.8, 10.6, 11.1, and 11.2 from Web Development with JavaServer Pages Second Edition by Duane Fields and Mark Kolb (figures 10.1, 10.5, 6.2, and 10.4). Figure 2.9 by Jean-Michel Garnier is reproduced with permission from the Apache Software Foundation. Manning Publications Co. Copyeditor: Liz Welch 32 Lafayette Place Typesetter: Tony Roberts Greenwich, CT 06830 Cover designer: Leslie Haimes ISBN 1-930110-50-2 Printed in the United States of America 12345678910– VHG – 05 04 03 02 brief contents PART 1GETTING STARTED WITH STRUTS ........................1 1 I Introduction 3 2 I Exploring the Struts architecture 29 3 I Building a simple application 59 4 I Configuring Struts components 105 PART 2RAISING YOUR FRAMEWORK ............................. 145 5 I Coping with ActionForms 147 6 I Wiring with ActionForwards 183 7 I Designing with ActionMappings 193 8 I Working with Action objects 207 9 I Extending ActionServlet 255 PART 3BUILDING YOUR PAGES .................................... 265 10 I Displaying dynamic content 267 v vi BRIEF CONTENTS 11 I Developing applications with Tiles 319 12 I Validating user input 365 13 I Localizing content 409 14 I Using data services with Struts 437 PART 4STRUTS BY EXAMPLE ......................................... 473 15 I Artimus: pulling out the stops 475 16 I Redux: migrating to Struts 1.1 533 17 I Velocity: replacing JSPs 555 contents foreword xix preface xxiii acknowledgments xxvi about this book xxviii PART 1GETTING STARTED WITH STRUTS ..................... 1 Introduction 3 1 1.1 What is this book about? 4 Who makes the Struts software? 4 I Why is Struts open source? 5 Why is it called Struts? 5 1.2 What are application frameworks? 5 Other types of frameworks 6 1.3 Enabling technologies 6 Hypertext Transfer Protocol (HTTP) 7 I Common Gateway Interface (CGI) 8 I Java servlets 9 I JavaServer Pages 10 JSP tags 11 I JavaBeans 12 I Model 2 14 1.4 Struts from 30,000 feet 14 Building a simple application 16 I Jump-starting development 16 I Where the rubber meets the road 18 Looking back 24 1.5 Summary 28 vii viii CONTENTS Exploring the Struts architecture 29 2 2.1 Talking the talk 30 2.2 Why we need Struts 30 One step back, three steps forward 30 I Enter Struts 31 Struts controller components 31 I Developing a web application with Struts 36 2.3 Why we need frameworks 37 The Web—a never-ending kluge 37 I The servlet solution 38 Servlet frameworks 39 I The whitebox-blackbox continuum 40 2.4 Struts, Model 2, and MVC 41 The evolution of MVC 41 I The rise of Model 2 42 Application layers—decoupling the view 43 How Struts implements Model 2, MVC, and layers 44 2.5 Struts control flow 46 The big picture 47 I The finer details 48 Is Struts performant? 52 2.6 The strengths and weaknesses of Struts 53 The weak points 54 I Struts’ strong points 56 2.7 Summary 58 Building a simple application 59 3 3.1 Strut by Strut 60 Why a logon application? 61 3.2 Touring a logon application 61 Start here 61 I Screens we’ll see 62 I The welcome screen 62 The logon screen 62 I The welcome screen, again 64 The welcome screen, good-bye 64 I Feature roundup 65 3.3 Dissecting the logon application 65 The browser source for the welcome screen 65 I The JSP source for the welcome screen 66 I The configuration source for the welcome screen 69 I The browser source for the logon screen 70 The configuration source for the logon screen 73 The LogonSubmit source 73 I The LogonForm source 74 The LogonAction source 77 I The LogoffAction source 83 3.4 Constructing an application 86 Defining the requirements 86 I Planning the application 87 Planning the source tree 90 I Setting up development tools 90 CONTENTS ix Setting up the build.xml file 92 I Setting up the web.xml file 92 I Setting up the struts-config.xml file 92 Testing the deployment 94 I Constructing our welcome page 95 Constructing the logon page 96 I Constructing the Constants class 98 I Constructing the other classes 99 I Creating the user directory 99 I Configuring the ActionErrors 100 I Compiling and testing the logon page 101 I Amending the welcome page 101 I The Struts ActionForward Action 102 3.5 Summary 104 Configuring Struts components 105 4 4.1 Three XMLs and a Properties file 106 The rest of the family 106 4.2 The web application deployment descriptor 107 The web.xml file 107 I ActionServlet parameters 110 4.3 The Struts configuration 113 Details, details 113 I Change management 115 The principle of Protected Variation 115 4.4 The Struts configuration elements 116 <global-exceptions> 118 I <form-beans> 119 <global-forwards> 120 I <action-mappings> 121 <controller> 123 I <message-resources> 123 <plug-in> 124 I <data-sources> 125 Rolling your own 126 I A skeleton Struts config 127 4.5 The application resources file 128 4.6 The Ant build file 130 4.7 Configuring the Struts core 133 Installing Java and a Java servlet container 133 Installing a development environment 134 Installing the Struts core files 134 4.8 Configuring the Tiles framework 134 4.9 Configuring the Struts Validator 136 4.10 Getting started with the Struts Blank application 137 4.11 Configuring modular applications 139 Divide and conquer 140 I Prefixing pages 142 Retrofitting a configuration 142 4.12 Sharing the Struts JAR 142 4.13 Summary 143 x CONTENTS PART 2RAISING YOUR FRAMEWORK.......................... 145 Coping with ActionForms 147 5 5.1 Garbage in, treasure out 148 ActionForm requirements 150 5.2 The many faces of an ActionForm 151 The ActionForm as a field harvester 151 I The ActionForm as a data buffer 153 I The ActionForm as a data validator 154 The ActionForm as a type transformer 155 I The ActionForm as a transfer object 155 I The ActionForm as a firewall 156 5.3 ActionForm design consequences 157 ActionForms may share names 157 I ActionForms may minimize custom code 158 I ActionForms may encapsulate helpers 158 ActionForms may nest other beans 158 5.4 ActionForm flavors 160 Map-backed ActionForms 160 I DynaActionForms 162 5.5 Why isn’t an ActionForm... 162 Why isn’t an ActionForm just a Map? 163 I Why isn’t an ActionForm a plain JavaBean? 163 I Why isn’t an ActionForm an interface? 163 5.6 Debriefing ActionForms 164 Implementing a business-layer interface 166 I Nesting a mutable value object 167 I Setting an immutable value object 168 Setting a mutable value object 169 I Using a factory method 170 Passing a Map 171 I Transferring values by reflection 173 Using an adaptor class 178 5.7 BaseForm 179 SessionLocale 180 I Dispatch 180 I Autopopulation 181 BaseMapForm 181 5.8 Summary 182 Wiring with ActionForwards 183 6 6.1 What ActionForwards do 184 6.2 How ActionForwards work 185 Forward versus redirect 185 6.3 Global and local forwards 187 6.4 Runtime parameters 188 CONTENTS xi Adding parameters in the page 188 Adding parameters in the Action class 188 6.5 Dynamic forwards 189 6.6 Why doesn’t the address bar change? 190 6.7 Rolling your own ActionForward 190 6.8 Summary 191 Designing with ActionMappings 193 7 7.1 Enter ActionMappings 194 The ActionMapping bean 195 The ActionMappings catalog 195 7.2 ActionMapping properties 196 The path property 197 I The forward property 198 The include property 198 I The type property 199 The className property 199 I The name property 199 The roles property 199 I The scope property 199 The validate property 200 I The input property 200 The parameter property 201 I The attribute property 202 The prefix and suffix properties 202 I The unknown ActionMapping 203 7.3 Nested components 203 Local forwards 203 I Local exceptions 204 7.4 Rolling your own ActionMapping 204 7.5 Summary 205 Working with Action objects 207 8 8.1 Ready, set, action! 208 8.2 Getting it done with Action objects 208 What are Actions? 209 I When are Actions called? 210 What do Actions do? 211 I What does an Action look like? 217 8.3 The standard Actions 219 Standard bridge Action classes 219 I Standard base Actions 222 8.4 Chaining Actions 228 Starting fresh 229 xii CONTENTS 8.5 Scaffold Actions 229 Forward-only Actions 230 I Helper Actions 236 8.6 Base View Actions 239 8.7 Helper Action techniques 240 Optional forwarding 241 I Calling ahead 242 Catching chained exceptions 243 I Smart error forwarding 245 Confirming success 246 I Alternate views 247 Reflecting methods 247 I Reflecting classes 248 8.8 Using smart forwarding 249 8.9 Summary 254 Extending ActionServlet 255 9 9.1 Where’s the beef? 256 The servlet’s Gang of Three 258 9.2 The RequestProcessor 259 The process method 260 I processRoles 260 9.3 The ExceptionHandler 262 9.4 PlugIn 263 9.5 Summary 264 PART 3BUILDING YOUR PAGES ................................

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