Design Patterns Explained A New Perspective on Object-Oriented Design

by Shalloway, Alan; Trott, James R.

• ISBN13: 9780321247148
• ISBN10: 0321247140
• Edition: 2nd
• Format: Paperback
• Copyright: 2004-10-12
• Publisher: Addison-Wesley Professional

Summary

"One of the great things about the book is the way the authors explain concepts very simply using analogies rather than programming examplesthis has been very inspiring for a product I'm working on: an audio-only introduction to OOP and software development." Bruce Eckel "...I would expect that readers with a basic understanding of object-oriented programming and design would find this book useful, before approaching design patterns completely.Design Patterns Explainedcomplements the existing design patterns texts and may perform a very useful role, fitting between introductory texts such as UML Distilled and the more advanced patterns books." James Noble Leverage the quality and productivity benefits of patternswithout the complexity!Design Patterns Explained, Second Editionis the field's simplest, clearest, most practical introduction to patterns. Using dozens of updated Java examples, it shows programmers and architects exactly how to use patterns to design, develop, and deliver software far more effectively. You'll start with a complete overview of the fundamental principles of patterns, and the role of object-oriented analysis and design in contemporary software development. Then, using easy-to-understand sample code, Alan Shalloway and James Trott illuminate dozens of today's most useful patterns: their underlying concepts, advantages, tradeoffs, implementation techniques, and pitfalls to avoid. Many patterns are accompanied by UML diagrams. Building on their best-selling First Edition, Shalloway and Trott have thoroughly updated this book to reflect new software design trends, patterns, and implementation techniques. Reflecting extensive reader feedback, they have deepened and clarified coverage throughout, and reorganized content for even greater ease of understanding. New and revamped coverage in this edition includes Better ways to start "thinking in patterns" How design patterns can facilitate agile development using eXtreme Programming and other methods How to use commonality and variability analysis to design application architectures The key role of testing into a patterns-driven development process How to use factories to instantiate and manage objects more effectively The Object-Pool Patterna new pattern not identified by the "Gang of Four" New study/practice questions at the end of every chapter Gentle yet thorough, this book assumes no patterns experience whatsoever. It's the ideal "first book" on patterns, and a perfect complement to Gamma's classicDesign Patterns. If you're a programmer or architect who wants the clearest possible understanding of design patternsor if you've struggled to make them work for youread this book.

Author Biography

Alan Shalloway is founder, CEO, and principal consultant of Net Objectives, an object-oriented consulting and training organization. An object-oriented consultant and software developer for over 20 years, he is a frequent speaker at leading development conferences, including SD Expo, Java One, OOP, and OOPSLA. He is a certified Scrum master. He is co-author of An Introduction to XML and its Family of Technologies. Shalloway holds a master's degree in computer science from MIT.

James R. Trott currently works as a senior consultant for a large financial institution in the Pacific Northwest. He has used object-oriented and pattern-based analysis techniques throughout his 20-year career in knowledge management and knowledge engineering. He holds a master of science in applied mathematics, an MBA, and a master of arts in intercultural studies.

© Copyright Pearson Education. All rights reserved.

Table of Contents

Preface	xix
From Object Orientation to Patterns to True Object Orientation	xxi
From Artificial Intelligence to Patterns to True Object Orientation	xxviii
A Note About Conventions Used in This Book	xxx
Feedback	xxxiv
New in the Second Edition	xxxiv
Acknowledgments	xxxv
PART I An Introduction to Object-Oriented Software Development	1	(46)
Chapter 1 The Object-Oriented Paradigm	3	(30)
Overview	3	(1)
Before the Object-Oriented Paradigm: Functional Decomposition	4	(2)
The Problem of Requirements	6	(2)
Dealing with Changes: Using Functional Decomposition	8	(3)
Dealing with Changing Requirements	11	(4)
The Object-Oriented Paradigm	15	(8)
Object-Oriented Programming in Action	23	(4)
Special Object Methods	27	(1)
Summary	28	(2)
Review Questions	30	(3)
Chapter 2 The UML-The Unified Modeling Language	33	(14)
Overview	33	(1)
What Is the UML?	33	(1)
Why Use the UML?	34	(1)
The Class Diagram	35	(7)
Interaction Diagrams	42	(3)
Summary	45	(1)
Review Questions	45	(2)
PART II The Limitations of Traditional Object-Oriented Design	47	(26)
Chapter 3 A Problem That Cries Out for Flexible Code	49	(12)
Overview	49	(1)
Extracting Information from a CAD/CAM System	49	(1)
Understand the Vocabulary	50	(2)
Describe the Problem	52	(3)
The Essential Challenges and Approaches	55	(3)
Summary	58	(1)
Review Questions	59	(2)
Chapter 4 A Standard Object-Oriented Solution	61	(12)
Overview	61	(1)
Solving with Special Cases	61	(9)
Summary	70	(1)
Review Questions	71	(2)
PART III Design Patterns	73	(142)
Chapter 5 An Introduction to Design Patterns	75	(18)
Overview	75	(1)
Design Patterns Arose from Architecture and Anthropology	76	(5)
Moving from Architectural to Software Design Patterns	81	(2)
Why Study Design Patterns?	83	(5)
Other Advantages of Studying Design Patterns	88	(2)
Summary	90	(1)
Review Questions	90	(3)
Chapter 6 The Facade Pattern	93	(8)
Overview	93	(1)
Introducing the Facade Pattern	93	(1)
Learning the Facade Pattern	94	(3)
Field Notes: The Facade Pattern	97	(2)
Relating the Facade Pattern to the CAD/CAM Problem	99	(1)
Summary	99	(1)
Review Questions	99	(2)
Chapter 7 The Adapter Pattern	101	(14)
Overview	101	(1)
Introducing the Adapter Pattern	101	(1)
Learning the Adapter Pattern	102	(5)
Field Notes: The Adapter Pattern	107	(4)
Relating the Adapter Pattern to the CAD/CAM Problem	111	(1)
Summary	112	(1)
Review Questions	112	(3)
Chapter 8 Expanding Our Horizons	115	(24)
Overview	115	(2)
Objects: The Traditional View and the New View	117	(2)
Encapsulation: The Traditional View and the New View	119	(4)
Find What Is Varying and Encapsulate It	123	(4)
Commonality and Variability Analysis and Abstract Classes	127	(3)
The Qualities of Agile Coding	130	(5)
Summary	135	(1)
Review Questions	136	(3)
Chapter 9 The Strategy Pattern	139	(20)
Overview	139	(1)
An Approach to Handling New Requirements	139	(3)
The International E-Commerce System Case Study: Initial Requirements	142	(1)
Handling New Requirements	143	(9)
The Strategy Pattern	152	(2)
Field Notes: Using the Strategy Pattern	154	(2)
Summary	156	(1)
Review Questions	157	(2)
Chapter 10 The Bridge Pattern	159	(34)
Overview	159	(1)
Introducing the Bridge Pattern	159	(2)
Learning the Bridge Pattern: An Example	161	(11)
An Observation About Using Design Patterns	172	(1)
Learning the Bridge Pattern: Deriving It	173	(10)
The Bridge Pattern in Retrospect	183	(1)
Field Notes: Using the Bridge Pattern	183	(5)
Summary	188	(3)
Review Questions	191	(2)
Chapter 11 The Abstract Factory Pattern	193	(22)
Overview	193	(1)
Introducing the Abstract Factory Pattern	193	(1)
Learning the Abstract Factory Pattern: An Example	194	(8)
Learning the Abstract Factory Pattern: Implementing It	202	(5)
Field Notes: The Abstract Factory Pattern	207	(4)
Relating the Abstract Factory Pattern to the CAD/CAM Problem	211	(1)
Summary	211	(1)
Review Questions	212	(3)
PART IV Putting It All Together: Thinking in Patterns	215	(36)
Chapter 12 How Do Experts Design?	217	(12)
Overview	217	(1)
Building by Adding Distinctions	217	(9)
Summary	226	(1)
Review Questions	226	(3)
Chapter 13 Solving the CAD/CAM Problem with Patterns	229	(22)
Overview	229	(1)
Review of the CAD/CAM Problem	229	(2)
Thinking in Patterns	231	(2)
Thinking in Patterns: Step 1	233	(1)
Thinking in Patterns: Step 2a	233	(6)
Thinking in Patterns: Step 2b	239	(5)
Thinking in Patterns: Step 2c	244	(1)
Thinking in Patterns: Steps 2a and 2b Repeated (Facade)	244	(1)
Thinking in Patterns: Steps 2a and 2b Repeated (Adapter)	245	(1)
Thinking in Patterns: Steps 2a and 2b Repeated (Abstract Factory)	246	(1)
Thinking in Patterns: Step 3	246	(1)
Comparison with the Previous Solution	247	(2)
Summary	249	(1)
Review Questions	250	(1)
PART V Toward a New Paradigm of Design	251	(62)
Chapter 14 The Principles and Strategies of Design Patterns	253	(16)
Overview	253	(1)
The Open-Closed Principle	254	(1)
The Principle of Designing from Context	255	(6)
The Principle of Encapsulating Variation	261	(1)
Abstract Classes vs. Interfaces	262	(2)
The Principle of Healthy Skepticism	264	(1)
Summary	265	(1)
Review Questions	266	(3)
Chapter 15 Commonality and Variability Analysis	269	(10)
Overview	269	(1)
Commonality and Variability Analysis and Application Design	269	(1)
Solving the CAD/CAM Problem with CVA	270	(7)
Summary	277	(1)
Review Questions	277	(2)
Chapter 16 The Analysis Matrix	279	(18)
Overview	279	(1)
In The Real World: Variations	279	(1)
The International E-Commerce System Case Study: Handling Variation	280	(11)
Held Notes	291	(3)
Summary	294	(1)
Review Questions	294	(3)
Chapter 17 The Decorator Pattern	297	(16)
Overview	297	(1)
A Little More Detail	297	(3)
The Decorator Pattern	300	(1)
Applying the Decorator Pattern to the Case Study	301	(4)
Another Example: Input/Output	305	(2)
Field Notes: Using the Decorator Pattern	307	(2)
The Essence of the Decorator Pattern	309	(1)
Summary	310	(1)
Review Questions	310	(3)
PART VI Other Values of Patterns	313	(32)
Chapter 18 The Observer Pattern	315	(16)
Overview	315	(1)
Categories of Patterns	315	(2)
More Requirements for the International E-Commerce Case Study	317	(2)
The Observer Pattern	319	(1)
Applying the Observer to the Case Study	319	(6)
Field Notes: Using the Observer Pattern	325	(2)
Summary	327	(1)
Review Questions	328	(3)
Chapter 19 The Template Method Pattern	331	(14)
Overview	331	(1)
More Requirements for the International E-Commerce Case Study	331	(1)
The Template Method Pattern	332	(1)
Applying the Template Method to the International E-Commerce Case Study	333	(1)
Using the Template Method Pattern to Reduce Redundancy	334	(6)
Field Notes: Using the Template Method Pattern	340	(1)
Summary	341	(2)
Review Questions	343	(2)
PART VII Factories	345	(52)
Chapter 20 Lessons from Design Patterns: Factories	347	(12)
Overview	347	(1)
Factories	347	(2)
The Universal Context Revisited	349	(2)
Factories Follow Our Guidelines	351	(2)
Limiting the Vectors of Change	353	(1)
Another Way to Think About It	354	(1)
Different Roles of Factories	355	(1)
Field Notes	355	(1)
Summary	356	(1)
Review Questions	356	(3)
Overview	359	(1)
Chapter 21 The Singleton Pattern and the Double-Checked Locking Pattern	359	(12)
Introducing the Singleton Pattern	360	(1)
Applying the Singleton Pattern to the Case Study	361	(3)
A Variant: The Double-Checked Locking Pattern	364	(3)
Reflections	367	(1)
Field Notes: Using the Singleton and Double-Checked Locking Patterns	368	(1)
Summary	369	(1)
Review Questions	369	(2)
Chapter 22 The Object Pool Pattern	371	(14)
Overview	371	(1)
A Problem Requiring the Management of Objects	372	(9)
The Object Pool Pattern	381	(1)
Observation: Factories Can Do Much More Than Instantiation	381	(3)
Summary	384	(1)
Review Questions	384	(1)
Chapter 23 The Factory Method Pattern	385	(8)
Overview	385	(1)
More Requirements for the Case Study	385	(1)
The Factory Method Pattern	386	(1)
Factory Method Pattern and Object-Oriented Languages	387	(1)
Field Notes: Using the Factory Method Pattern	388	(2)
Summary	390	(1)
Review Questions	390	(3)
Chapter 24 Summary of Factories	393	(4)
Overview	393	(1)
Steps in the Software Process	393	(2)
Parallels in Factories and XP Practices	395	(1)
Scaling Systems	395	(2)
PART VIII Endings and Beginnings	397	(22)
Chapter 25 Design Patterns Reviewed: A Summation and a Beginning	399	(10)
Overview	399	(1)
A Summary of Object-Oriented Principles	400	(1)
How Design Patterns Encapsulate Implementations	401	(1)
Commonality and Variability Analysis and Design Patterns	401	(1)
Decomposing a Problem Domain into Responsibilities	402	(1)
Patterns and Contextual Design	403	(1)
Relationships Within a Pattern	404	(1)
Design Patterns and Agile Coding Practices	405	(1)
Field Notes	406	(1)
Summary	407	(1)
Review Questions	408	(1)
Chapter 26 Bibliography	409	(10)
Design Patterns Explained: The Web Site Companion	410	(1)
Recommended Reading	410	(2)
Recommended Reading for Java Programmers	412	(1)
Recommended Reading for C++ Programmers	413	(1)
Recommended Reading for COBOL Programmers	414	(1)
Recommended Reading on eXtreme Programming	414	(1)
Recommended Reading on General Programming	415	(1)
Personal Favorites	415	(4)
Index	419

Excerpts

Preface Should You Buy the Second Edition If You Already Own the First? The answer, of course, is yes! Here's why. Since the first edition was written, we have learned so much more about design patterns, including the following: How to use commonality and variability analysis to design application architectures How design patterns relate to and actually facilitate eXtreme programming (XP) and agile development. How testing is a first principle of quality coding. Why the use of factories to instantiate and manage objects is critical Which set of patterns are essential for students to help them learn how to think in patterns This book covers all of these topics. We have deepened and clarified what we had before and have added some new content that you will find very helpful, including the following: Chapter 15: Commonality and Variability Analysis Chapter 20: Lessons from Design Patterns: Factories Chapter 21: The Object-Pool Pattern (a pattern not covered by the Gang of Four) Chapter 22: Factories Summarized We have changed the order in which we present some of the patterns. This sequence is more helpful for the students in our courses as they learn the ideas behind patterns. We have touched every chapter, incorporating the feedback we have received from our many readers over these past three years. And, to help students, we have created study questions for each chapter (with answers on the book's companion Web site). We can honestly say this is one of the few second editions that is definitely worth buying -- even if you have the first one. We would love to hear what you think. --Alan and Jim Design patterns and object-oriented programming. They hold such promise to make your life as a software designer and developer easier. Their terminology is bandied about every day in the technical and even the popular press. It can be hard to learn them, however, to become proficient with them, to understand what is really going on. Perhaps you have been using an object-oriented or object-based language for years. Have you learned that the true power of objects is not inheritance, but is in "encapsulating behaviors"? Perhaps you are curious about design patterns and have found the literature a bit too esoteric and high-falutin. If so, this book is for you. It is based on years of teaching this material to software developers, both experienced and new to object orientation. It is based upon the belief--and our experience--that when you understand the basic principles and motivations that underlie these concepts, why they are doing what they do, your learning curve will be incredibly shorter. And in our discussion of design patterns, you will understand the true mindset of object orientation, which is a necessity before you can become proficient. As you read this book, you will gain a solid understanding of 12 core design patterns and a pattern used in analysis. You will learn that design patterns do not exist in isolation, but work in concert with other design patterns to help you create more robust applications. You will gain enough of a foundation that you will be able to read the design pattern literature, if you want to, and possibly discover patterns on your own. Most importantly, you will be better equipped to create flexible and complete software that is easier to maintain. Although the 12 patterns we teach here are not all of the patterns you should learn, an understanding of these will enable you to learn the others on your own more easily. Instead of giving you more patterns than you need to get started, we have included pattern-related issues that will