Clean Architecture

Practical Software Architecture Solutions from the Legendary Robert C. Martin ("Uncle Bob")

By applying universal rules of software architecture, you can dramatically improve developer productivity throughout the life of any software system. Now, building upon the success of his best-selling books Clean Code and The Clean Coder, legendary software craftsman Robert C. Martin ("Uncle Bob") reveals those rules and helps you apply them.

Martin's Clean Architecture doesn't merely present options. Drawing on over a half-century of experience in software environments of every imaginable type, Martin tells you what choices to make and why they are critical to your success. As you've come to expect from Uncle Bob, this book is packed with direct, no-nonsense solutions for the real challenges you'll face-the ones that will make or break your projects.

• Learn what software architects need to achieve-and core disciplines and practices for achieving it
• Master essential software design principles for addressing function, component separation, and data management
• See how programming paradigms impose discipline by restricting what developers can do
• Understand what's critically important and what's merely a "detail"
• Implement optimal, high-level structures for web, database, thick-client, console, and embedded applications
• Define appropriate boundaries and layers, and organize components and services
• See why designs and architectures go wrong, and how to prevent (or fix) these failures
  Clean Architecture is essential reading for every current or aspiring software architect, systems analyst, system designer, and software manager-and for every programmer who must execute someone else's designs.

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Autorentext

Robert C. Martin ("Uncle Bob") has been a programmer since 1970. He is founder of Uncle Bob Consulting, LLC, and cofounder with his son Micah Martin of The Clean Coders LLC. Martin has published dozens of articles in various trade journals and is a regular speaker at international conferences and trade shows. He has authored and edited many books, including: Designing Object Oriented C++ Applications Using the Booch Method, Patterns Languages of Program Design 3, More C++ Gems, Extreme Programming in Practice, Agile Software Development: Principles, Patterns, and Practices, UML for Java Programmers, Clean Code, and The Clean Coder. A leader in the industry of software development, Martin served for three years as editor-in-chief of the C++ Report, and he served as the first chairman of the Agile Alliance.

Inhalt

Foreword xv

Preface xix

Acknowledgments xxiii

About the Author xxv

Part I: Introduction 1

Chapter 1: What Is Design and Architecture? 3

The Goal? 4

Case Study 5

Conclusion 12

Chapter 2: A Tale of Two Values 13

Behavior 14

Architecture 14

The Greater Value 15

Eisenhower's Matrix 16

Fight for the Architecture 18

Part II: Starting with the Bricks: Programming Paradigms 19

Chapter 3: Paradigm Overview 21

Structured Programming 22

Object-Oriented Programming 22

Functional Programming 22

Food for Thought 23

Conclusion 24

Chapter 4: Structured Programming 25

Proof 27

A Harmful Proclamation 28

Functional Decomposition 29

No Formal Proofs 30

Science to the Rescue 30

Tests 31

Conclusion 31

Chapter 5: Object-Oriented Programming 33

Encapsulation? 34

Inheritance? 37

Polymorphism? 40

Conclusion 47

Chapter 6: Functional Programming 49

Squares of Integers 50

Immutability and Architecture 52

Segregation of Mutability 52

Event Sourcing 54

Conclusion 56

Part III: Design Principles 57

Chapter 7: SRP: The Single Responsibility Principle 61

Symptom 1: Accidental Duplication 63

Symptom 2: Merges 65

Solutions 66

Conclusion 67

Chapter 8: OCP: The Open-Closed Principle 69

A Thought Experiment 70

Directional Control 74

Information Hiding 74

Conclusion 75

Chapter 9: LSP: The Liskov Substitution Principle 77

Guiding the Use of Inheritance 78

The Square/Rectangle Problem 79

LSP and Architecture 80

Example LSP Violation 80

Conclusion 82

Chapter 10: ISP: The Interface Segregation Principle 83

ISP and Language 85

ISP and Architecture 86

Conclusion 86

Chapter 11: DIP: The Dependency Inversion Principle 87

Stable Abstractions 88

Factories 89

Concrete Components 91

Conclusion 91

Part IV: Component Principles 93

Chapter 12: Components 95

A Brief History of Components 96

Relocatability 99

Linkers 100

Conclusion 102

Chapter 13: Component Cohesion 103

The Reuse/Release Equivalence Principle 104

The Common Closure Principle 105

The Common Reuse Principle 107

The Tension Diagram for Component Cohesion 108

Conclusion 110

Chapter 14: Component Coupling 111

The Acyclic Dependencies Principle 112

Top-Down Design 118

The Stable Dependencies Principle 120

The Stable Abstractions Principle 126

Conclusion 132

Part V: Architecture 133

Chapter 15: What Is Architecture? 135

Development 137

Deployment 138

Operation 138

Maintenance 139

Keeping Options Open 140

Device Independence 142

Junk Mail 144

Physical Addressing 145

Conclusion 146

Chapter 16: Independence 147

Use Cases 148

Operation 149

Development 149

Deployment 150

Leaving Options Open 150

Decoupling Layers 151

Decoupling Use Cases 152

Decoupling Mode 153

Independent Develop-ability 153

Independent Deployability 154

Duplication 154

Decoupling Modes (Again) 155

Conclusion 158

Chapter 17: Boundaries: Drawing Lines 159

A Couple of Sad Stories 160

FitNesse 163

Which Lines Do You Draw, and When Do You Draw Them? 165

What About Input and Output? 169

Plugin Architecture 170

The Plugin Argument 172

Conclusion 173

Chapter 18: Boundary Anatomy 175

Boundary Crossing 176

The Dreaded Monolith 176

Deployment Components 178

Threads 179

Local Processes 179

Services 180

Conclusion 181

Chapter 19: Policy and Level 183

Level 184

Conclusion 187

Chapter 20: Business Rules 189

Entities 190

Use Cases 191

Request and Response Models 193

Conclusion 194

Chapter 21: Screaming Architecture 195

The Theme of an Architecture 196

The Purpose of an Architecture 197

But What About the Web? 197

Frameworks Are Tools, Not Ways of Life 198

Testable Architectures 198

Conclusion 199

Chapter 22: The Clean Architecture 201

The Dependency Rule 203

A Typical Scenario 207

Conclusion 209

Chapter 23: Presenters and Humble Objects 211

The Humble Object Pattern 212

Presenters and Views 212

Testing and Architecture 213

Database Gateways 214

Data Mappers 214

Service Listeners 215

Conclusion 215

Chapter 24: Partial Boundaries 217

Skip the Last Step 218

One-Dimensional Boundaries 219

Facades 220

Conclusion 220

Chapter 25: Layers and Boundaries 221

Hunt the Wumpus 222

Clean Architecture? 223

Crossing the Streams 226

Splitting the Streams 227

Conclusion 228

Chapter 26: The Main Component 231

The Ultimate Detail 232

Conclusion 237

Chapter 27: Services: Great and Small 239

Service Architecture? 240

Service Benefits? 240

The Kitty Problem 242

Objects to the Rescue 244

Component-Based Services 245

Cross-Cutting Concerns 246

Conclusion 247

Chapter 28: The Test Boundary 249

Tests as System Components 250

Design for Testability 251

The Testing API 252

Conclusion 253

Chapter 29: Clean Embedded Architecture 255

App-titude Test 258

The Target-Hardware Bottleneck 261

Conclusion 273

Part VI: Details 275

Chapter 30: The Database Is a Detail…