Preface

17

Target Group and Prerequisites

17

Structure of the Book

17

Conventions

19

Source Code and Examples

20

Acknowledgments

20

1 Introduction to Object-Oriented Programming

23

1.1 The Need for a Better Abstraction

23

1.1.1 The Evolution of Programming Languages

23

1.1.2 Moving Toward Objects

24

1.2 Classes and Objects

25

1.2.1 What Are Objects?

25

1.2.2 Introducing Classes

26

1.2.3 Defining a Class Interface

28

1.3 Establishing Boundaries

29

1.3.1 Encapsulation and Implementation Hiding

29

1.3.2 Understanding Visibility Sections

31

1.4 Reuse

31

1.4.1 Composition

31

1.4.2 Inheritance

32

1.4.3 Polymorphism

33

1.5 Object Management

34

1.6 UML Tutorial: Class Diagram Basics

35

1.6.1 What Are Class Diagrams?

36

1.6.2 Classes

37

1.6.3 Attributes

37

1.6.4 Operations

38

1.6.5 Associations

39

1.6.6 Notes

40

1.7 Summary

40

2 Working with Objects

41

2.1 Defining Classes

41

2.1.1 Creating a Class

42

2.1.2 Component Declarations

43

2.1.3 Implementing Methods

50

2.2 Working with Objects

51

2.2.1 Object References

52

2.2.2 Creating Objects

52

2.2.3 Object Reference Assignments

53

2.2.4 Accessing Instance Components

55

2.2.5 Accessing Class Components

58

2.2.6 Working with Events

60

2.2.7 Working with Functional Methods

64

2.2.8 Chaining Method Calls Together

67

2.3 Building Your First Object-Oriented Program

70

2.3.1 Creating the Report Program

70

2.3.2 Adding in the Local Class Definition

74

2.4 Working with Global Classes

76

2.4.1 Understanding the Class Pool Concept

76

2.4.2 Getting Started with the Class Builder Tool

76

2.4.3 Creating Global Classes

78

2.4.4 Using the Form-Based Editor

80

2.4.5 Using the Source Code Editor

88

2.5 Developing Classes Using ABAP Development Tools

88

2.5.1 What Is Eclipse?

89

2.5.2 Setting Up the ABAP Development Tools Environment

89

2.5.3 Working with the ABAP Development Tools Class Editor

93

2.6 Working with Constructor Expressions

101

2.7 UML Tutorial: Object Diagrams

104

2.8 Summary

106

3 Encapsulation and Implementation Hiding

107

3.1 Lessons Learned from Procedural Programming

107

3.1.1 Decomposing the Functional Decomposition Process

108

3.1.2 Case Study: A Procedural Code Library in ABAP

110

3.1.3 Moving Toward Objects

115

3.2 Data Abstraction with Classes

116

3.3 Defining Component Visibilities

117

3.3.1 Working with Visibility Sections

118

3.3.2 Understanding the Friend Concept

121

3.4 Hiding the Implementation

123

3.5 Designing by Contract

124

3.6 UML Tutorial: Sequence Diagrams

125

3.7 Summary

126

4 Object Initialization and Cleanup

129

4.1 Understanding the Object Creation Process

129

4.2 Working with Constructors

133

4.2.1 Defining Constructors

134

4.2.2 Understanding How Constructors Work

134

4.2.3 Class Constructors

136

4.3 Taking Control of the Instantiation Process

137

4.3.1 Controlling the Instantiation Context

138

4.3.2 Implementing the Singleton Pattern

139

4.3.3 Working with Factory Methods

141

4.4 Garbage Collection

143

4.5 Tuning Performance

144

4.5.1 Design Considerations

144

4.5.2 Lazy Initialization

144

4.5.3 Reusing Objects

145

4.5.4 Making Use of Class Attributes

146

4.6 UML Tutorial: State Machine Diagrams

146

4.7 Summary

147

5 Inheritance and Composition

149

5.1 Generalization and Specialization

149

5.1.1 Inheritance Defined

150

5.1.2 Defining Inheritance Relationships in ABAP Objects

151

5.1.3 Working with Subclasses

156

5.1.4 Inheritance as a Living Relationship

157

5.2 Inheriting Components

159

5.2.1 Designing the Inheritance Interface

159

5.2.2 Visibility of Instance Components in Subclasses

161

5.2.3 Visibility of Class Components in Subclasses

162

5.2.4 Redefining Methods

162

5.2.5 Instance Constructors

165

5.2.6 Class Constructors

166

5.3 The Abstract and Final Keywords

166

5.3.1 Abstract Classes and Methods

166

5.3.2 Final Classes

170

5.3.3 Final Methods

172

5.4 Inheritance Versus Composition

173

5.5 Working with ABAP Refactoring Tools

176

5.6 UML Tutorial: Advanced Class Diagrams, Part I

179

5.6.1 Generalizations

179

5.6.2 Dependencies and Composition

179

5.6.3 Abstract Classes and Methods

180

5.7 Summary

182

6 Polymorphism

183

6.1 Object Reference Assignments Revisited

183

6.1.1 Static and Dynamic Types

184

6.1.2 Casting

186

6.2 Dynamic Method Call Binding

189

6.3 Interfaces

191

6.3.1 Interface Inheritance Versus Implementation Inheritance

192

6.3.2 Defining Interfaces

193

6.3.3 Implementing Interfaces

197

6.3.4 Working with Interfaces

200

6.3.5 Nesting Interfaces

203

6.3.6 When to Use Interfaces

205

6.4 UML Tutorial: Advanced Class Diagrams, Part II

207

6.4.1 Interfaces

207

6.4.2 Providing and Required Relationships with Interfaces

208

6.4.3 Static Attributes and Methods

209

6.5 Summary

209

7 Component-Based Design Concepts

211

7.1 Understanding SAP’s Component Model

211

7.2 The Package Concept

214

7.2.1 Why Do You Need Packages?

214

7.2.2 Introducing Packages

215

7.2.3 Creating Packages Using the Package Builder

217

7.2.4 Embedding Packages

224

7.2.5 Defining Package Interfaces

225

7.2.6 Creating Use Accesses

228

7.2.7 Performing Package Checks

229

7.2.8 Restriction of Client Packages

231

7.3 Package Design Concepts

233

7.4 UML Tutorial: Package Diagrams

235

7.5 Summary

237

8 Error Handling with Exception Classes

239

8.1 Lessons Learned from Prior Approaches

239

8.1.1 Lesson 1: Exception Handling Logic Gets in the Way

239

8.1.2 Lesson 2: Exception Handling Requires Varying Amounts of Data

240

8.1.3 Lesson 3: The Need for Transparency

241

8.2 The Class-Based Exception Handling Concept

241

8.3 Creating Exception Classes

243

8.3.1 Understanding Exception Class Types

243

8.3.2 Local Exception Classes

244

8.3.3 Global Exception Classes

245

8.3.4 Defining Exception Texts

247

8.3.5 Mapping Exception Texts to Message Classes

249

8.4 Dealing with Exceptions

250

8.4.1 Handling Exceptions

250

8.4.2 Cleaning Up the Mess

254

8.5 Raising and Forwarding Exceptions

255

8.5.1 System-Driven Exceptions

255

8.5.2 Raising Exceptions Programmatically

256

8.5.3 Propagating Exceptions

260

8.5.4 Resumable Exceptions

263

8.6 UML Tutorial: Activity Diagrams

267

8.7 Summary

269

9 Unit Tests with ABAP Unit

271

9.1 ABAP Unit Overview

271

9.1.1 Unit Testing Terminology

272

9.1.2 Understanding How ABAP Unit Works

272

9.1.3 ABAP Unit and Production Code

274

9.2 Creating Unit Test Classes

274

9.2.1 Unit Test Naming Conventions

274

9.2.2 Generating Test Classes for Global Classes

275

9.2.3 Defining Test Attributes

276

9.2.4 Building Test Methods

277

9.2.5 Working with Fixtures

278

9.2.6 Working with Test Seams

278

9.2.7 Defining Reusable Test Classes

280

9.3 Assertions in ABAP Unit

280

9.3.1 Creating and Evaluating Custom Constraints

281

9.3.2 Applying Multiple Constraints

282

9.4 Managing Dependencies

283

9.4.1 Dependency Injection

283

9.4.2 Private Dependency Injection

284

9.4.3 Partially Implemented Interfaces

284

9.4.4 Working with Test Doubles

285

9.4.5 Other Sources of Information

287

9.5 Case Study: Creating a Unit Test in ABAP Unit

288

9.6 Executing Unit Tests

291

9.6.1 Integration with the ABAP Workbench

291

9.6.2 Creating Favorites in the ABAP Unit Test Browser

292

9.6.3 Integration with the Code Inspector

293

9.7 Evaluating Unit Test Results

294

9.8 Measuring Code Coverage

294

9.9 Moving Toward Test-Driven Development

296

9.10 Behavior-Driven Development

296

9.11 UML Tutorial: Use Case Diagrams

297

9.11.1 Use Case Terminology

297

9.11.2 An Example Use Case

298

9.11.3 The Use Case Diagram

299

9.11.4 Use Cases for Requirements Verification

300

9.11.5 Use Cases and Testing

301

9.12 Summary

301

10 Business Object Development with BOPF

303

10.1 What Is BOPF?

303

10.2 Anatomy of a Business Object

305

10.2.1 Nodes

306

10.2.2 Actions

310

10.2.3 Determinations

312

10.2.4 Validations

313

10.2.5 Associations

315

10.2.6 Queries

318

10.3 Working with the BOPF Client API

319

10.3.1 API Overview

320

10.3.2 Creating Business Object Instances and Node Rows

323

10.3.3 Searching for Business Object Instances

326

10.3.4 Updating and Deleting Business Object Node Rows

327

10.3.5 Executing Actions

328

10.3.6 Working with the Transaction Manager

329

10.4 Where to Go from Here

330

10.4.1 Looking at the Big Picture

330

10.4.2 Enhancing Business Objects

331

10.5 UML Tutorial: Advanced Sequence Diagrams

331

10.5.1 Creating and Deleting Objects

332

10.5.2 Depicting Control Logic with Interaction Frames

333

10.6 Summary

334

11 ABAP RESTful Application Programming Model

335

11.1 Introduction

335

11.1.1 What Is the ABAP RESTful Application Programming Model?

335

11.1.2 Relationship to SAP Gateway

337

11.1.3 Business Object Runtime

338

11.1.4 Behavior Definitions

340

11.1.5 Model Classes

342

11.2 CDS and SAP Gateway Service Bindings

347

11.2.1 CDS Views

347

11.2.2 Associations

348

11.3 Modeling Behavior Using Object-Oriented Techniques

350

11.3.1 Creating the Service

350

11.3.2 Object-Oriented Implementation

360

11.4 Summary

370

12 ABAP Cloud

371

12.1 Introduction to SAP Business Technology Platform

372

12.1.1 What Is SAP Business Technology Platform?

372

12.1.2 Core Capabilities of SAP Business Technology Platform

374

12.1.3 ABAP and SAP Business Technology Platform

376

12.2 ABAP Environment Overview

377

12.2.1 Core Concepts

378

12.2.2 Key Architectural Components

383

12.3 Setting Up Your Cloud Development Environment

386

12.3.1 Transitioning from On-Premise to Cloud Development

386

12.3.2 Creating Your SAP BTP ABAP Environment

388

12.4 Case Study: Implementing ABAP RESTful Application Programming Model Elements via ABAP Cloud

395

12.4.1 Recreation of ABAP RESTful Application Programming Model Objects

396

12.4.2 Publishing and Consuming the Service

397

12.5 Summary

397

13 Best Practices and Design Patterns

399

13.1 Object-Oriented Analysis and Design

399

13.2 Creational Patterns

401

13.2.1 When to Use Creational Patterns in ABAP

403

13.2.2 Singleton Pattern

404

13.2.3 Factory Method Pattern

405

13.3 Structural Patterns

408

13.3.1 When to Use Structural Patterns in ABAP

409

13.3.2 Adapter Pattern

411

13.3.3 Decorator Pattern

414

13.4 Behavioral Patterns

419

13.4.1 When to Use Behavioral Patterns in ABAP

421

13.4.2 Strategy Pattern

421

13.5 Summary

425

A Installing the Eclipse IDE

427

A.1 Installing the Java SDK

427

A.2 Installing Eclipse

428

A.3 Installing the ABAP Development Tools

430

A.4 Where to Go to Find Help

432