Java Enterprise Design Patterns: Patterns in Java

497 Pages·2001·3.101 MB·English

by  Mark Grand

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Patterns in JavaTM, Volume 3
MARK GRAND
MARK GRAND
John Wiley & Sons, Inc.
New York ● ChichesterJo●hWne Winihleeiym &● SBorniss,b aInnce.● Singapore ● Toronto
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Publisher: Robert Ipsen
Editor: Theresa Hudson
Developmental Editor: Kathryn A. Malm
Managing Editor: Angela Smith
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This book is printed on acid-free paper.
Copyright © 2002 by Mark Grand. All rights reserved.
Published by John Wiley & Sons, Inc., New York
Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system or
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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:
Grand, Mark.
Java Enterprise design patterns / Mark Grand.
p. cm.
ISBN 0-471-33315-8 (pbk.: alk. paper)
1. Java (Computer program language) 2. Web servers. 3. Object-
oriented programming (Computer science) I. Title.
QA76.73.J38 G72 2001
005. 13'3—dc21 2001045611
Printed in the United States of America.
10 9 8 7 6 5 4 3 2 1
C O N T E N T S
Acknowledgments vii
About the Author viii
Chapter 1 Introduction to Software Patterns 1
Description of Patterns 2
Pattern Name 3
Synopsis 3
Context 3
Forces 3
Solution 4
Consequences 4
Implementation 4
Known Uses 4
Code Example 4
Related Patterns 4
A Very Brief History of Patterns 5
Organization of This Book 5
iv ■ CONTENTS
Chapter 2 Overview of UML 7
Class Diagram 8
Collaboration Diagram 18
Statechart Diagram 26
Deployment Diagram 28
Chapter 3 The Software Life Cycle 29
Chapter 4 Transaction Patterns 33
Acid Transaction 37
Composite Transaction 55
Two Phase Commit 65
Audit Trail 75
Chapter 5 Distributed Architecture Patterns 81
Shared Object 83
Object Request Broker 89
Object Replication 99
Redundant Independent Objects 109
Prompt Repair 115
Mobile Agent 119
Demilitarized Zone 129
Process Pairs 133
Chapter 6 Distributed Computing Patterns 137
Object Identifier 139
Registry 149
Protection Proxy 157
Publish-Subscribe 175
Retransmission 187
Mailbox 195
Heavyweight/Lightweight 203
Heartbeat 209
Connection Multiplexing 229
Chapter 7 Concurrency Patterns 275
Session Object 277
Lock File 285
Static Locking Order 291
Optimistic Concurrency 297
Thread Pool 303
Ephemeral Cache Item 325
Transaction State Stack 337
Contents ■ v
Chapter 8 Temporal Patterns 347
Time Server 349
Versioned Object 355
Temporal Property 373
Chapter 9 Database Patterns 387
Persistence Layer 389
CRUD 407
Stale Object 413
Type Conversion 423
IsDirty 431
Lazy Retrieval 439
Appendix A Persistence Framework 445
Bibliography 475
Index 477

A C K N O W L E D G M E N T S
This book would not have been possible without the inspiration, encour-
agement and assistance of others.
I want to thank Brad Appleton for his diligent reviews and concern
with form.
Wolfgang W. Keller provided extensive feedback on the transaction
patterns chapter.
Frank Sauer provided excellent feedback on the database patterns
chapter.
I also want to thank the members of the pattern discussion group at
University of Illinois, Champaign-Urbana, for their invaluable comments
on my manuscript: Joe Yoder, Brian Foote, Hiroaki Nakamura, Roger
Whitney, Ralph Johnson, Brian Marick, Wanghong Yuan, Paul Rubel,
Frederico Balaguer, Alejandra Garrido, Don Roberts, Zhijiang “John” Han,
Weerasak Witthawuskul, Peter Hatch, Dragos Malolescu, and Les Tyrrell.
Last, but not least, I would like to thank my wife Nicole for her sup-
port and encouragement through the most difficult of times. This book
could not have been finished without her understanding and patience.
A B O U T T H E A U T H O R

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Mark Grandis a conTsultant specializing in distributed systems, object-
oriented design, and Java. He is currently working on an open source
framework for gluing components and programs into an application.

Mark Grand is the author of a series of books titled Patterns in

Java. He is a consultant who specializes in Distributed Systems, Object

Oriented Design, and Java. He was the architect of the first commercial

B2B e-commerce product for the Internet.

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C H A P T E R
Introduction
to Software Patterns
Software patternsare reusable solutions to recurring problems that occur
during software development. For purposes in this book, we refer to soft-
ware patterns simply as patterns.
What makes a bright, experienced programmer so much more produc-
tive than a bright but inexperienced programmer? Experience. Experience
gives programmers wisdom. As programmers gain experience, they recog-
nize the similarity between new problems and those problems that they have
solved before. With even more experience, they recognize that the solutions
for similar problems follow recurring patterns. Experienced programmers
recognize the situations where these patterns apply and quickly draw on
existing solutions without having to stop, analyze the problems, and then
pose possible strategies.
When a programmer discovers a pattern, it’s just an insight. In most
cases, to go from a nonverbalized insight to a well-thought-out idea that
the programmer can clearly articulate is surprisingly difficult. It’s also an
extremely valuable step. When we understand a pattern well enough to put
it into words, we are able to intelligently combine it with other patterns.
More important, once put into words, a pattern can be used in discussions
among programmers who know the pattern. That allows programmers to
more effectively collaborate and combine their wisdom. It can also help to
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