Refactoring to Patterns is a book by Joshua Kerievsky published by Addison Wesley in August 2004.
It is the marriage of refactoring -- the process of improving the design of existing code -- with patterns, the classic solutions to recurring design problems.
Refactoring to Patterns suggests that using patterns to improve an existing design is better than using patterns early in a new design.
This is true whether code is years old or minutes old. We improve designs with patterns by applying sequences of low-level design transformations, known as refactorings.
Whether you are doing greenfield or legacy development, the refactorings and design ideas in this book will help you with your work.
This book assumes you are familiar with design concepts like tight- or loose-coupling and object-oriented concepts like inheritance, polymorphism, encapsulation, composition, interfaces, abstract and concrete classes, abstract and static methods and so forth.
I use Java examples in this book. I find that Java tends to be easy for most object-oriented programmers to read. I've gone out of my way to not use fancy Java features, so whether you code in C++, C#, VB.NET, Python, Ruby, Smalltalk or some other object-oriented language, you ought be able to understand the Java code in this book.
This book is closely tied to Martin Fowler's classic book, Refactoring [F].
To understand the pattern-directed refactorings in this book, you don't need to know every refactoring listed above. Instead, you can follow the example code that illustrates how the above refactorings are implemented. However, if you want to get the most out of this book, I do recommend that you have Refactoring [F] close by your side. It's an invaluable refactoring resource, as well as a useful aid for understanding this book.
The patterns I write about come from the classic book, Design Patterns [DP], as well as from authors such as Kent Beck, Bobby Woolf and myself. These are patterns that my colleagues and I have refactored to, towards or away from on real-world projects. By learning the art of pattern-directed refactorings, you'll understand how to refactor or towards patterns not mentioned in this book.
You don't need expert knowledge of these patterns to read this book, though some knowledge of patterns is useful. To help you understand the patterns I've written about, this book includes brief pattern summaries, UML sketches of patterns and many example implementations of patterns. To get a more detailed understanding of the patterns, I'd recommend that you study this book in conjunction with the patterns literature I reference.
This book uses UML 2.0 diagrams. If you don't know UML very well, you're in good company. I know the basics. While writing this book, I kept the third edition of Fowler's UML Distilled close by my side and referred to it often.
"For refactoring to be valuable it must be going somewhere, not just an abstract intellectual exercise. Patterns document program structures with known good properties. Put the two together and you have Refactoring to Patterns. If you want your refactorings to go somewhere, I suggest you read and apply Refactoring to Patterns."
- Kent Beck"In the GoF book we claimed that design patterns are targets for refactorings. This book finally shows that we didn’t lie. By doing so, Joshua’s book will deepen your understanding of both refactoring and design patterns."
- Erich Gamma, Eclipse Java Development Tools lead, IBM"Now the connection between software patterns and agile development is finally told."
- Ward Cunningham"Refactoring to patterns is a revolutionary approach to applying patterns that combines the top-down utility of design patterns with the bottom-up discovery of iterative development and continuous refactoring. Any serious software developer should be using this approach to discover new opportunities to use patterns to improve their code."
- Bobby Woolf, Consulting I/T Specialist, IBM Software Services for Web-Sphere, and coauthor of Enterprise Integration Patterns (Addison-Wesley) and The Design Patterns Smalltalk Companion (Addison-Wesley)"With this unique catalog of design-level refactorings Joshua Kerievsky has given refactoring an entirely new dimension. Refactoring to Patterns shows developers how to make design-level improvements that simplify everyday work. This book is an invaluable reference for the refactoring practitioner."
- Sven Gorts"This book refactors and restructures GoF, and much more. Refactoring to Patterns takes a subject that has been presented as static and rigid and makes it dynamic and flexible, converting it into a human process with experiments, mistakes, and corrections so you understand that good designs do not occur by turning some series of cranks—they evolve through struggle and reflection."
- Bruce Eckel, President of Mindview, Inc., and author of Thinking in Java/Thinking in C++ (Prentice Hall)"Kerievsky has also restructured the presentation to make it far clearer and easier to assimilate. Indeed, he has solved a number of the organization problems that I have struggled with in Thinking in Patterns. This book is a clear introduction and combination of the disciplines of testing, refactoring, and patterns, and it is filled with easy reading, good sense, and great insights."
- Bruce Eckel, President of Mindview, Inc., and author of Thinking in Java/Thinking in C++ (Prentice Hall)"The first time I met Joshua, I was struck by the depth of his passion for understanding, applying, and teaching design patterns. Great teachers care deeply about their subject and how to share it. I think Joshua is a great teacher—and developer—and that we can all benefit from his insight."
- Craig Larman, Chief Scientist, Valtech, and author of Applying UML and Patterns, Second Edition (Prentice Hall) and Agile and Iterative Development (Addison-Wesley)"Refactoring to Patterns is important not only because it provides step-by-step instructions on how to improve your code through the methodical introduction of appropriate patterns, but more so because it teaches the principles that underlie the design patterns implemented. This book should be useful for novice and expert designers alike. This is a great book."
- Kyle Brown, IBM Software Services for WebSphere, and author of Enterprise Java™ Programming with IBM® WebSphere®, Second Edition (Addison-Wesley)
Joshua is the founder and CEO of Industrial Logic, one of the oldest and most well-respected agile consultancies on the planet. Since 1996, Joshua and his global network of colleagues have helped people in teams across many industries leverage the wisdom and power of modern product development methods.
An early pioneer and practitioner of Extreme Programming, Lean Software Development and Lean Startup, Joshua most recently crafted Modern Agile to help people and organizations benefit from a principle-based approach to agility.
