Mastering Enterprise JavaBeans™ and the Java 2 Platform, Enterprise Edition - Roman E
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Mastering Enterprise
JavaBeans™
and the Java™ 2 Platform,
Enterprise Edition
Ed Roman
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Wiley Computer Publishing
John Wiley & Sons, Inc.
NEW YORK • CHICHESTER • WEINHEIM • BRISBANE • SINGAPORE • TORONTO
Publisher: Robert Ipsen
Editor: Robert M. Elliott
Managing Editor: Brian Snapp
Electronic Products, Associate Editor: Mike Sosa
Text Design & Composition: Rob Mauhar
Designations used by companies to distinguish their products are often claimed as trademarks. In all instances where John Wiley & Sons, Inc., is aware of a claim, the product names appear in initial capital or all capital letters. Readers, however, should contact the appropriate companies for more complete information regarding trademarks and registration.
Sun, Sun Microsystems, the Sun Logo, Enterprise JavaBeans, Java, and JNDI are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and other countries.
This book is printed on acid-free paper.
Copyright © 1999 by Ed Roman. All rights reserved.
Published by John Wiley & Sons, Inc.
Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4744. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, e-mail: PERMREQ@WILEY.COM.
This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold with the understanding that the publisher is not engaged in professional services. If professional advice or other expert assistance is required, the services of a competent professional person should be sought.
Library of Congress Cataloging-in-Publication Data:
0-471-33229-1
Printed in the United States of America.
10 9 8 7 6 5 4 3 2 1
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A D VA N C E P R A I S E
What People Are Saying about Ed Roman’s
Mastering Enterprise JavaBeans and the Java 2 Platform, Enterprise Edition...
“Ed Roman has done a great job of explaining a complex topic: how to build Java applications for the middle tier. Not only does he explain how to program with EJB, he explains how to design applications so that they can use EJB intelligently. This is a great starting place for programmers who are trying to move from simplistic client/server applications to true multi-tier development using the official Java middle-tier platform.”
—Roger Sessions, President, Objectwatch
Author, “ObjectWatch Newsletter”
“This book is a must-have for developers who want to jumpstart their EJB development process. Ed Roman shows the right way to use the J2EE technology with indepth examples and coding patterns from the real world. We recommend this book as part of our education materials for both in-house staff and customer engagements.”
—William W. Lee, Chief Technology Officer, The Theory Center
“Enterprise JavaBeans and the J2EE are among the most important technologies in enterprise computing. Organizations that are exploring or implementing missioncritical, Web-based, and distributed systems should understand the role that the Enterprise Java platform can play. Ed Roman has done an excellent job of taking this complex subject and explaining it in a clear and practical manner. I recommend this book to anyone who wants to increase their knowledge and expertise in building robust, ‘real-world’ computing systems.”
—Doug Hibberd, Chief Technology Officer, iMARK.COM
“This book explains all fundamentals of EJB wrapped up in an easy to follow set of examples. It is easy enough for the beginner and covers enough for more experienced users to like it. It also provides the reader with a guide to what you should consider when buying an EJB server, as well as a brief look into the future and what’s coming next in this exciting new technology.”
—Rickard ÖBerg, Software Architect, DreamBean
“This book starts off innocently enough with the idea of explaining Enterprise JavaBeans. However, by the end, you realize that Ed Roman has effectively unwrapped the onion that is today’s multi-tier architecture and shown how J2EE can revolutionize how systems are architected. I highly recommend this book to anyone who wishes to keep up with the latest in Java technology and internet systems architecture.”
—Mike Perham, Senior Web Developer, living.com
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To my family:
Mom, Dad, and Mike
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C O N T E N TS
Preface |
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xix |
About the Author |
xxii |
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Introduction |
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xxiii |
Part I: |
Overview |
1 |
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Chapter 1 Server-side Component Architectures |
3 |
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The Need for a Server-Side Component Architecture |
4 |
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Software Components |
4 |
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Component Architectures |
7 |
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The Needs of the Server Side |
12 |
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Multi-tier Architectures |
13 |
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Server-Side Component Architecture Solutions |
23 |
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Microsoft’s Distributed interNet Applications Architecture |
24 |
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Sun Microsystems’s Java 2 Platform, Enterprise Edition (J2EE) |
25 |
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The Object Management Group’s CORBA Standard |
26 |
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The Java 2 Platform, Enterprise Edition |
27 |
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Why J2EE? |
27 |
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The J2EE Technologies |
29 |
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Enterprise JavaBeans (EJB) |
31 |
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Remote Method Invocation (RMI) and RMI-IIOP |
32 |
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Java Naming and Directory Interface (JNDI) |
33 |
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Java Database Connectivity (JDBC) |
34 |
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Java Transaction API (JTA) and Java Transaction Service (JTS) |
35 |
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Java Messaging Service (JMS) |
36 |
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Java Servlets and Java Server Pages (JSPs) |
37 |
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Java IDL |
38 |
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JavaMail |
38 |
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Connectors |
39 |
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The Extensible Markup Language (XML) |
40 |
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Summary |
40 |
Chapter 2 Enterprise JavaBeans Overview |
41 |
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Who’s Who in Enterprise JavaBeans |
42 |
v
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vi |
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M A S T E R I N G E N T E R P R I S E J A V A B E A N S |
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The Six Parties |
43 |
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The Bean Provider |
45 |
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The EJB Server and EJB Container Providers |
46 |
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The Application Assembler |
49 |
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The EJB Deployer |
50 |
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The System Administrator |
50 |
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Enterprise Beans |
51 |
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Types of Beans |
51 |
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Motivation for Multiple Bean Types |
59 |
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Overview of EJB Container and EJB Server Responsibilities |
59 |
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Resource Management and Bean Life Cycle Management |
62 |
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State Management |
62 |
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Transactions |
63 |
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Security |
64 |
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Persistence |
64 |
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Remote Accessibility and Location Transparency |
64 |
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Glue-Code and Bean Installation Tools |
65 |
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Specialized Container Features |
65 |
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Summary |
67 |
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Part II: |
Developing Beans |
69 |
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Chapter 3 Introduction to Session Beans |
71 |
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What Constitutes an Enterprise Bean? |
71 |
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The Enterprise Bean Class |
72 |
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The EJB Object |
73 |
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The Home Object |
77 |
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Deployment Descriptors |
78 |
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Bean-Specific Properties |
81 |
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Ejb-jar File |
81 |
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Summary of Terms |
82 |
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What Is a Session Bean? |
83 |
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Session Bean Lifetime |
83 |
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Conversational versus Nonconversational Session Beans |
84 |
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All Session Beans’ Methods Are Serialized |
85 |
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Understanding How to Write Session Beans |
85 |
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setSessionContext(SessionContext ctx) |
86 |
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ejbCreate(...) |
86 |
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ejbPassivate() |
87 |
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ejbActivate() |
88 |
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ejbRemove() |
89 |
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Business Methods |
89 |
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Understanding How to Call Session Beans |
90 |
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Looking Up a Home Object |
91 |
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Contents |
|
vii |
Creating an EJB Object |
94 |
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Calling a Method |
94 |
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Destroying the EJB Object |
94 |
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Summary |
95 |
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Chapter 4 The Basics of Stateless Session Beans |
97 |
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Characteristics of Stateless Session Beans |
97 |
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No Conversational State |
97 |
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Only One Way to Initialize Stateless Sessions |
98 |
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Containers Can Pool and Reuse Stateless Sessions |
98 |
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EJB Object Decoupling |
99 |
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Writing a “Hello, World!” Stateless Session Bean |
99 |
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Constructing the “Hello, World!” Remote Interface |
100 |
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Implementing the “Hello, World!” Bean |
101 |
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Constructing the “Hello, World!” Home Interface |
104 |
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Writing the Deployment Descriptor |
105 |
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The Environment Properties |
107 |
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The Ejb-jar File |
108 |
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Deploying the Bean |
110 |
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Writing Client Code for Our Stateless Bean |
111 |
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Running the System |
112 |
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Summary |
114 |
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Chapter 5 The Basics of Stateful Session Beans |
115 |
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Characteristics of Stateful Session Beans |
115 |
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Achieving the Effect of Pooling with Stateful Beans |
115 |
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The Rules Governing Conversational State |
117 |
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Activation/Passivation Callbacks |
118 |
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A Simple Stateful Session Bean |
118 |
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Stateful or Stateless? |
128 |
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Myths and Facts about Statelessness |
128 |
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Summary |
130 |
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Chapter 6 Adding Functionality to Your Beans |
133 |
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EJB Contexts: Your Gateway to the Container |
133 |
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Session Bean Contexts |
134 |
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SessionContext.getEJBObject() |
136 |
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Understanding EJB Security |
136 |
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Step 1: Authentication |
137 |
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Step 2: Authorization |
137 |
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Security Propagation |
141 |
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Understanding EJB Object Handles |
142 |
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Example: The Puzzle Game “Fazuul” |
143 |
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What Is Fazuul? |
143 |
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viii |
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M A S T E R I N G E N T E R P R I S E J A V A B E A N S |
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Specifying Fazuul in EJB |
145 |
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Making the Game Data-Driven through Environment Properties |
145 |
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Implementing Fazuul |
146 |
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Running the Client |
170 |
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Summary |
174 |
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Chapter 7 Introduction to Entity Beans |
175 |
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Persistence Concepts |
176 |
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Java Object Serialization |
176 |
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Object-Relational Mapping |
176 |
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Object Databases |
178 |
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What Is an Entity Bean? |
179 |
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Files Included with Entity Beans |
181 |
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Features of Entity Beans |
182 |
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Entity Beans Are Long-Lived |
183 |
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Entity Beans Survive Failures |
183 |
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Entity Bean Instances Are a View into a Database |
183 |
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Several Entity Bean Instances May Represent the Same |
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Underlying Data |
184 |
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Entity Bean Instances Can Be Pooled |
185 |
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There Are Two Ways to Persist Entity Beans |
188 |
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Entity Beans Can Be Created, Removed, or Found |
190 |
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Entity Beans Can Represent Legacy Data and Legacy Systems |
191 |
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Entity Beans Can Be Modified without Going through EJB |
191 |
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Developing and Using Entity Beans |
192 |
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Creation of Entity Beans: ejbCreate() |
193 |
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Finding Existing Entity Beans: ejbFind() |
194 |
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Destruction of Entity Beans: ejbRemove() |
197 |
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Entity Contexts |
197 |
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getEJBObject() |
199 |
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getPrimaryKey() |
199 |
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Putting It All Together: Walking through an Entity Bean |
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Life Cycle |
202 |
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Summary |
204 |
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Chapter 8 Writing Bean-Managed Persistent Entity Beans |
207 |
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Implementation Guidelines for Bean-Managed Persistence |
207 |
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Bean-Managed Persistence Example: A Bank Account |
211 |
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Account.java |
212 |
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AccountHome.java |
213 |
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AccountPK.java |
214 |
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AccountBean.java |
214 |
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AccountException.java |
227 |
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Client.java |
228 |
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|
|
Contents |
|
ix |
|
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The Deployment Descriptor |
230 |
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Environment Properties |
231 |
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Setting Up the Database |
231 |
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Running the Client Program |
232 |
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Server-Side Output |
232 |
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Client-Side Output |
234 |
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Summary |
234 |
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Chapter 9 Writing Container-Managed Persistent Entity Beans |
235 |
||
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Container-Managed Fields |
235 |
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Primary Key Class |
236 |
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Implementation Guidelines for Container-Managed |
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Persistence |
237 |
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Container-Managed Persistence Example: A Product Line |
241 |
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Product.java |
242 |
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ProductHome.java |
242 |
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ProductPK.java |
244 |
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ProductBean.java |
244 |
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Client.java |
250 |
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The Deployment Descriptor |
252 |
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Running the Client Program |
253 |
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Server-Side Output |
254 |
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Client-Side Output |
255 |
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Promises and Realities: Bean-Managed Persistence versus |
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Container-Managed Persistence |
255 |
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Promise: Container-Managed Persistence Reduces Code |
256 |
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Promise: Container-Managed Persistence Reduces Bugs |
256 |
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Promise: Container-Managed Persistence Makes It Easy to |
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Port to Different Databases |
257 |
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Resolving Your EJB Debugging Problems |
258 |
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Summary |
260 |
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Part III: |
Advanced Enterprise JavaBeans Concepts |
261 |
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Chapter 10 |
Transactions |
263 |
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The Motivation for Transactions |
264 |
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Atomic Operations |
264 |
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Network or Machine Failure |
265 |
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Multiple Users Sharing Data |
266 |
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The Benefits of Transactions |
266 |
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The ACID Properties |
268 |
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Transactional Models |
270 |
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|
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Flat Transactions |
270 |
|
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x |
|
M A S T E R I N G E N T E R P R I S E J A V A B E A N S |
Nested Transactions |
272 |
Other Transactional Models |
274 |
Enlisting in Transactions with Enterprise JavaBeans |
274 |
Transaction Models Supported |
274 |
Underlying Transaction System Abstraction |
274 |
Declarative and Programmatic Transactions |
275 |
Controlling How Your Enterprise Beans Are Enrolled in |
|
Transactions |
276 |
EJB Transaction Attribute Values |
278 |
Transactional Isolation |
281 |
The Need for Concurrency Control |
282 |
Isolation and EJB |
283 |
The Dirty Read Problem |
285 |
The Unrepeatable Read Problem |
287 |
The Phantom Problem |
288 |
Transaction Isolation Summary |
289 |
Distributed Transactions |
290 |
Durability and the Two-Phase Commit Protocol |
290 |
The Transactional Communications Protocol and |
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Transaction Contexts |
291 |
Programmatic Transactions in EJB |
293 |
CORBA’s Object Transaction Service (OTS) |
293 |
The Java Transaction Service (JTS) |
294 |
The Java Transaction API (JTA) |
294 |
Declarative versus Programmatic Transactions Example |
297 |
How to Control Transactions from Client Code |
298 |
Designing Transactional Conversations in EJB |
299 |
Summary |
302 |
Chapter 11 CORBA and RMI-IIOP |
303 |
What Is CORBA? |
303 |
CORBA as the Basis for EJB |
304 |
Why Should I Care about CORBA? |
304 |
Benefits of Using CORBA |
305 |
Drawbacks of CORBA |
305 |
Understanding How CORBA Works |
306 |
Object Request Brokers |
306 |
Object Implementations and Object References |
308 |
Object Adapters |
308 |
Repositories |
309 |
OMG’s Interface Definition Language |
310 |
OMG IDL Maps to Concrete Languages |
312 |
Static Invocations |
313 |
Dynamic Invocations |
314 |
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