Design Patterns in ABAP Objects

Use design patterns to step up your object-oriented ABAP game, starting with MVC! Want to create objects only when needed? Call objects only when required, minimizing runtime and memory costs? Reduce errors and effort by only coding an object once? Future-proof your code with a flexible design? Design patterns are the answer! With this guide, you'll get practical examples for every design pattern that will have you writing readable, flexible, and reusable code in no time!Highlights include:- MVC (model, view, controller) pattern-Singleton pattern-Factory pattern-Builder pattern-Observer pattern-Visitor pattern-Lazy initialization pattern-Template method-Strategy pattern-Decorator pattern-ABAP-specific examples-Anti-patterns Highlights: MVC (model, view, controller) pattern Singleton pattern Factory pattern Builder pattern Observer pattern Visitor pattern Lazy initialization pattern Template method Strategy pattern Decorator pattern ABAP-specific examples Anti-patterns

See design patterns in action with real-world SAP applications

Autorentext
Dr. Kerem Koseoglu is a freelance SAP software architect, working professionally since 2000. He specializes in the development of comprehensive applications using design patterns and also conducts technical training related to design patterns. He has participated in global software development projects, taking diverse roles including lead architect, team lead, developer, technical advisor, instructor, and project manager. His former publications include four books and countless articles for technical magazines in Turkey. He has a Ph.D. in organizational behavior.

Zusammenfassung
Want to create objects only when needed? Call objects only when required, minimizing runtime and memory costs? Reduce errors and effort by only coding an object once? Future-proof your code with a flexible design? With this guide, you'll get practical examples for every design pattern that will have you writing readable, flexible code in no time.

Inhalt
... Preface ... 17

... Design Pattern Categories ... 19

... How to Learn ... 20

PART I ... Architectural Design Patterns ... 25

1 ... MVC ... 27

1.1 ... Case Study: Read, Process, Display, and Post ... 28

1.2 ... Passing Select Options ... 33

1.3 ... Distributing Application Logic ... 34

1.4 ... Related Patterns ... 34

1.5 ... Summary ... 35

PART II ... Creational Design Patterns ... 37

2 ... Abstract Factory ... 39

2.1 ... Case Study: Log Analysis ... 40

2.2 ... Related Patterns ... 47

2.3 ... Summary ... 47

3 ... Builder ... 49

3.1 ... Case Study: Jobs for Text Files ... 49

3.2 ... When to Use ... 66

3.3 ... Privacy ... 66

3.4 ... Summary ... 67

4 ... Factory ... 69

4.1 ... Case Study: FI Documents for Parties ... 69

4.2 ... Advantages ... 75

4.3 ... Related Patterns ... 75

4.4 ... Summary ... 76

5 ... Lazy Initialization ... 77

5.1 ... Case Study: Logging Errors ... 77

5.2 ... Advantages ... 81

5.3 ... Related Patterns ... 81

5.4 ... Summary ... 82

6 ... Multiton ... 83

6.1 ... Case Study: Vendor Balance ... 84

6.2 ... When to Use ... 88

6.3 ... When to Avoid ... 88

6.4 ... State Modification ... 89

6.5 ... Summary ... 89

7 ... Prototype ... 91

7.1 ... Case Study: Item Clone ... 91

7.2 ... Changing Class Properties ... 95

7.3 ... Clone Operations ... 96

7.4 ... Related Patterns ... 96

7.5 ... Summary ... 97

8 ... Singleton ... 99

8.1 ... Case Study: Subcomponents ... 99

8.2 ... Advantages and Disadvantages ... 106

8.3 ... Related Patterns ... 106

8.4 ... Summary ... 106

PART III ... Structural Design Patterns ... 107

9 ... Adapter ... 109

9.1 ... Case Study: Project Management Tools ... 109

9.2 ... Glue Code ... 118

9.3 ... Two-Way Adapters ... 118

9.4 ... Legacy Classes ... 122

9.5 ... Summary ... 122

10 ... Bridge ... 123

10.1 ... Case Study: Messaging Framework ... 123

10.2 ... Advantages ... 131

10.3 ... Summary ... 131

11 ... Composite ... 133

11.1 ... Recursive Programming: A Refresher ... 133

11.2 ... Case Study: HR Positions ... 137

11.3 ... Advantages ... 144

11.4 ... Disadvantages ... 144

11.5 ... When to Use ... 145

11.6 ... Related Patterns ... 145

11.7 ... Summary ... 146

12 ... Data Access Object ... 147

12.1 ... Case Study: Potential Customers ... 147

12.2 ... Redundant Code Prevention ... 152

12.3 ... Related Patterns ... 153

12.4 ... Summary ... 153

13 ... Decorator ... 155

13.1 ... Case Study: User Exit ... 155

13.2 ... Advantages and Challenges ... 161

13.3 ... Related Patterns ... 162

13.4 ... Summary ... 162

14 ... Façade ... 165

14.1 ... Case Study: Bonus Calculation ... 166

14.2 ... When and Where to Use ... 168

14.3 ... Related Patterns ... 170

14.4 ... Summary ... 170

15 ... Flyweight ... 171

15.1 ... Case Study: Negative Stock Forecast ... 171

15.2 ... Disadvantages ... 181

15.3 ... When to Use ... 181

15.4 ... Related Patterns ... 182

15.5 ... Summary ... 182

16 ... Property Container ... 185

16.1 ... Case Study: Enhancing an SAP Program ... 185

16.2 ... Static vs. Instance Containers ... 194

16.3 ... Sharing Variables ... 195

16.4 ... Variable Uniqueness ... 196

16.5 ... Related Patterns ... 196

16.6 ... Summary ... 198

17 ... Proxy ... 199

17.1 ... Case Study: Sensitive Salary Information ... 199

17.2 ... When to Use ... 206

17.3 ... Related Patterns ... 207

17.4 ... Summary ... 207

18 ... Chain of Responsibility ... 209

18.1 ... Case Study: Purchase Order Approver Determination ... 209

18.2 ... Risks ... 217

18.3 ... Related Patterns ... 217

18.4 ... Summary ... 218

PART IV ... Behavioral Design Patterns ... 219

19 ... Command ... 221

19.1 ... Case Study: SD Documents ... 221

19.2 ... When to Use or Avoid ... 229

19.3 ... Related Patterns ... 229

19.4 ... Summary ... 230

20 ... Mediator ... 231

20.1 ... Case Study: Stock Movement Simulation ... 232

20.2 ... When to Use ... 241

20.3 ... Disadvantages ... 241

20.4 ... Summary ... 241

21 ... Memento ... 243

21.1 ... Case Study: Budget Planning ... 243

21.2 ... Risks ... 252

21.3 ... Redo ... 253

21.4 ... Summary ... 254

22 ... Observer ... 255

22.1 ... Case Study: Target Sales Values ... 256

22.2 ... Advantages ... 261

22.3 ... Disadvantages ... 261

22.4 ... Multiple Subjects ... 262

22.5 ... Related Patterns ... 263

22.6 ... Summary ... 264

23 ... Servant ... 265

23.1 ... Case Study: Address Builder ... 266

23.2 ... Extensions ... 274

23.3 ... Related Patterns ... 275

23.4 ... Summary ... 275

24 ... State ... 277

24.1 ... Case Study: Authorization-Based Class Behavior ... 277

24.2 ... Advantages ... 283

24.3 ... Related Patterns ... 284

24.4 ... Summary ... 284

25 ... Strategy ... 285

25.1 ... Case Study: Sending Material Master Data ... 286

25.2 ... Advantages ... 291

25.3 ... Passing Data to the Strategy Object ... 291

25.4 ... Optional Strategies ... 293

25.5 ... Intermediate Abstract Classes ... 297

25.6 ... Related Patterns ... 302

25.7 ... Summary ..…