Java Application Architecture: Modularity Patterns with Examples Using OSGi

by Kirk Knoernschild

Overview

“I’m dancing! By god I’m dancing on the walls. I’m dancing on the ceiling. I’m ecstatic. I’m overjoyed. I’m really, really pleased.”

–From the Foreword by Robert C. Martin (a.k.a. Uncle Bob)

 

This isn’t the first book on Java application architecture. No doubt it won’t be the last. But rest assured, this title is different. The way we develop Java applications is about to change, and this title explores the new way of Java application architecture.

 

Over the past several years, module frameworks have been gaining traction on the Java platform, and upcoming versions of Java will include a module system that allows you to leverage the power of modularity to build more resilient and flexible software systems. Modularity isn’t a new concept. But modularity will change the way we develop Java applications, and you’ll only be able to realize the benefits if you understand how to design more modular software systems.

 

Java Application Architecture will help you

 

• Design modular software that is extensible, reusable, maintainable, and adaptable
• Design modular software today, in anticipation of future platform support for modularity
• Break large software systems into a flexible composite of collaborating modules
• Understand where to place your architectural focus
• Migrate large-scale monolithic applications to applications with a modular architecture
• Articulate the advantages of modular software to your team

 

Java Application Architecture lays the foundation you’ll need to incorporate modular design thinking into your development initiatives. Before it walks you through eighteen patterns that will help you architect modular software, it lays a solid foundation that shows you why modularity is a critical weapon in your arsenal of design tools. Throughout, you’ll find examples that illustrate the concepts. By designing modular applications today, you are positioning yourself for the platform and architecture of tomorrow. That’s why Uncle Bob is dancing.

Product Details

ISBN-13:	9780132874748
Publisher:	Pearson Education
Publication date:	03/16/2012
Series:	Robert C. Martin Series
Sold by:	Barnes & Noble
Format:	eBook
Pages:	384
File size:	5 MB
Age Range:	18 Years

About the Author

Kirk Knoernschild is a software developer who has filled most roles on the software development team. Kirk is the author of Java Design: Objects, UML, and Process (Addison-Wesley, 2002), and he contributed to No Fluff Just Stuff 2006 Anthology (Pragmatic Bookshelf, 2006). Kirk is an open source contributor, has written numerous articles, and is a frequent conference speaker. He has trained and mentored thousands of software professionals on topics including Java/J2EE, modeling, software architecture and design, component-based development, service-oriented architecture, and software process. You can visit his website at techdistrict.kirkk.com.

Table of Contents

Foreword by Robert C. Martin xix

Foreword by Peter Kriens xxi

Acknowledgments xxv

About the Author xxvii

Introduction 1

Object-Oriented Design 2

Logical versus Physical Design 3

Modularity 4

Who This Book Is For 6

How This Book Is Organized 7

Pattern Form 10

Pattern Catalog 12

The Code 13

An Opening Thought on the Modularity Patterns 14

Reference 14

Part I: The Case for Modularity 15

Chapter 1: Module Defined 17

1.1 Defining a Module 17

1.2 Succinct Definition of a Software Module 20

1.3 Conclusion 20

Chapter 2: The Two Facets of Modularity 21

2.1 The Runtime Model 21

2.2 The Development Model 22

2.3 Modularity Today 25

2.4 Conclusion 27

Chapter 3: Architecture and Modularity 29

3.1 Defining Architecture 29

3.2 A Software Architecture Story 30

3.3 The Goal of Architecture 33

3.4 Modularity: The Missing Ingredient 36

3.5 Answering Our Questions 43

3.6 Conclusion 44

3.7 References 44

Chapter 4: Taming the Beast Named Complexity 45

4.1 Enterprise Complexity 46

4.2 Technical Debt 47

4.3 Design Rot 48

4.4 Cyclic Dependencies–The Death Knell 50

4.5 Joints, Modules, and SOLID 56

4.6 Managing Complexity 57

4.7 Benefits of Modularity 59

4.8 Conclusion 60

4.9 References 60

Chapter 5: Realizing Reuse 61

5.1 The Use/Reuse Paradox 62

5.2 The Reuse Disclaimer 63

5.3 Reuse or Use 64

5.4 Modular Tension 65

5.5 Modular Design 66

5.6 Conclusion 67

5.7 Reference 68

Chapter 6: Modularity and SOA 69

6.1 All the Way Down, Revisited 69

6.2 Granularity–Architecture’s Nemesis 72

6.3 An Alternate View 79

6.4 Conclusion 80

Chapter 7: Reference Implementation 83

7.1 Why No OSGi? 83

7.2 Background on This Exercise: Building the System 84

7.3 Version 1 85

7.4 First Refactoring 87

7.5 Second Refactoring 90

7.6 Third Refactoring 93

7.7 Fourth Refactoring 95

7.8 Fifth Refactoring 98

7.9 Sixth Refactoring 99

7.10 Seventh Refactoring 102

7.11 The Postmortem 103

7.12 Conclusion 110

7.13 Reference 110

Part II: The Patterns 111

Chapter 8: Base Patterns 115

Manage Relationships 116

Module Reuse 125

Cohesive Modules 139

Chapter 9: Dependency Patterns 145

Acyclic Relationships 146

Levelize Modules 157

Physical Layers 162

Container Independence 170

Independent Deployment 178

Reference 185

Chapter 10: Usability Patterns 187

Published Interface 188

External Configuration 200

Default Implementation 206

Module Facade 212

Chapter 11: Extensibility Patterns 221

Abstract Modules 222

Implementation Factory 229

Separate Abstractions 237

Reference 244

Chapter 12: Utility Patterns 245

Colocate Exceptions 246

Levelize Build 253

Test Module 263

Part III: Poma and OSGi 271

Chapter 13: Introducing OSGi 273

13.1 Some History 273

13.2 Benefits of OSGi 274

13.3 Digesting OSGi 276

13.4 OSGi Bundle 277

13.5 OSGi Runtime Management 279

13.6 The Two Facets of Modularity, Revisited 279

13.7 OSGi and the Patterns 279

Chapter 14: The Loan Sample and OSGi 283

14.1 Getting Started 283

14.2 The Manifests 285

14.3 μServices 286

14.4 Installation and Execution 292

14.5 Conclusion 293

Chapter 15: OSGi and Scala 295

15.1 Getting Started 295

15.2 The Scala Code 296

15.3 Scala Bean Configuration 299

15.4 Scala μService Configuration 299

15.5 Building the Scala Module 300

15.6 Installation and Execution 300

15.7 Conclusion 301

Chapter 16: OSGi and Groovy 303

16.1 Getting Started 303

16.2 The Groovy Code 304

16.3 Groovy Bean Configuration 306

16.4 Groovy Service Configuration 307

16.5 Building the Groovy Module 307

16.6 Installation and Execution 308

16.7 Conclusion 309

Chapter 17: Future of OSGi 311

17.1 OSGi as an Enabler 312

17.2 The Disruption 312

17.3 The Power of Ecosystems 314

17.4 The Ecosystem 316

17.5 Conclusion 317

Appendix: SOLID Principles of Class Design 319

Single Responsibility Principle (SRP) 320

Open Closed Principle (OCP) 320

Liskov Substitution Principle (LSP) 323

Dependency Inversion Principle (DIP) 325

Interface Segregation Principle 327

Composite Reuse Principle (CRP) 329

References 335

Index 337

Editorial Reviews

The fundamentals never go out of style, and in this book Kirk returns us to the fundamentals of architecting economically interesting software-intensive systems of quality. You’ll find this work to be well-written, timely, and full of pragmatic ideas.”

–Grady Booch, IBM Fellow

“Along with GOF’s Design Patterns, Kirk Knoernschild’s Java Application Architecture is a must-own for every enterprise developer and architect and on the required reading list for all Paremus engineers.”

–Richard Nicholson, Paremus CEO, President of the OSGi Alliance

“In writing this book, Kirk has done the software community a great service: He’s captured much of the received wisdom about modularity in a form that can be understood by newcomers, taught in computer science courses, and referred to by experienced programmers. I hope this book finds the wide audience it deserves.”

–Glyn Normington, Eclipse Virgo Project Lead

“Our industry needs to start thinking in terms of modules–it needs this book!”

–Chris Chedgey, Founder and CEO, Structure 101

“In this book, Kirk Knoernschild provides us with the design patterns we need to make modular software development work in the real world. While it’s true that modularity can help us manage complexity and create more maintainable software, there’s no free lunch. If you want to achieve the benefits modularity has to offer, buy this book.”

–Patrick Paulin, Consultant and Trainer, Modular Mind

“Kirk has expertly documented the best practices for using OSGi and Eclipse runtime technology. A book any senior Java developer needs to read to better understand how to create great software.”

–Mike Milinkovich, Executive Director, Eclipse Foundation

From the Publisher