Domain-driven Design with Java: Building scalable and maintainable Java applications with DDD principles

Cover....2

Title Page....3

Copyright Page....4

Dedication Page....5

About the Author....6

About the Reviewer....7

Acknowledgement....8

Preface....9

Table of Contents....15

1. Understanding Domain-driven Design....23

Introduction....23

Structure....24

Objectives....24

Importance of domain-driven design....25

Connecting business goals with technical implementation....27

Core concepts and methodologies....28

Strategic aspect of DDD....30

Tactical aspect of DDD....30

Conclusion....31

Points to remember....32

Multiple choice questions....32

Answers....34

References....34

2. Strategic DDD Concepts....36

Introduction....36

Structure....36

Objectives....37

Domains and subdomains....37

Example scenario with EcoTrack Logistics....39

Understanding bounded contexts....41

Context mapping techniques....44

Aligning business strategy with software design....46

Conclusion....47

Points to remember....47

Multiple choice questions....48

Answers....49

References....50

3. Tactical DDD Implementation....51

Introduction....51

Structure....51

Technical requirements....52

Objectives....52

Entities and value objects....52

Entities pitfalls....54

Builders and domain-specific language....60

Value object....62

Aggregates and aggregate roots....66

Services and their roles....69

Implementing repositories....73

Conclusion....75

Points to remember....76

Multiple choice questions....77

Answers....78

References....79

4. Testing and Validating DDD Applications....81

Introduction....81

Structure....82

Technical requirements....82

Objectives....82

Introduction to testing in DDD....83

Unit testing DDD components....83

Defining the domain components....85

Using tests to validate expected behavior....87

Enhancing your tests....93

Using ArchUnit for architectural validation....97

Conclusion....100

Points to remember....101

Multiple choice questions....102

Answers....104

References....104

5. DDD in Microservices, Monoliths, and Distributed Systems....106

Introduction....106

Structure....107

Technical requirements....107

Objectives....108

DDD in monolithic architecture....108

Creating the domain layer and organizing packages....112

Creating the application layer....117

Creating the controller layer....118

Creating the infrastructure layer....120

DDD in microservices architecture....121

Need for microservices....126

Applying DDD in distributed systems....128

Refactoring legacy code to align with DDD principles....131

Conclusion....134

Points to remember....134

Multiple choice questions....135

Answers....137

References....138

6. Integrating DDD with Clean Architecture....139

Introduction....139

Structure....139

Technical requirements....140

Objectives....140

Overview of Clean Architecture....140

Combining DDD with Clean Architecture....143

Creating well-defined boundaries with Clean Architecture and DDD....143

Creating a bridge between the core application and external systems....146

Structuring code for maintainability....149

Using and combining each approach....151

Conclusion....152

Points to remember....153

Multiple choice questions....154

Answers....156

References....156

7. DDD and Data Modeling....158

Introduction....158

Structure....158

Technical requirements....158

Objectives....159

Principles of DDD in data modeling....159

Modeling data in SQL databases....162

Jakarta Persistence in action....163

Modeling data in NoSQL databases....167

Conclusion....171

Points to remember....171

Multiple choice questions....172

Answers....175

8. Enterprise Java with Jakarta EE....176

Introduction....176

Structure....176

Technical requirements....177

Objectives....177

Applying DDD with Jakarta EE....178

Leveraging Jakarta Data for better encapsulation....180

Integrating DDD into enterprise Java applications....183

Conclusion....187

Points to remember....187

Multiple choice questions....188

Answers....191

9. Enterprise Java with Spring....192

Introduction....192

Structure....192

Technical requirements....193

Objectives....193

Overview of Spring Framework with DDD....193

Applying DDD with Spring Boot....196

Creating and setting up a new Spring Boot project....196

Defining the core domain entities....197

Shaping the repository and services....198

Exposing the service through REST endpoints....200

Polishing error handling....202

Ensuring code behavior with unit tests....204

Conclusion....208

Points to remember....208

Multiple choice questions....209

Answers....211

10. Eclipse MicroProfile and Domain-driven Design....212

Introduction....212

Structure....212

Technical requirements....213

Objectives....213

Understanding Eclipse MicroProfile and its purpose....214

Clarifying Jakarta EE and MicroProfile similarities....214

Eclipse MicroProfile architecture and specifications....215

Integrating Eclipse MicroProfile with DDD....217

Practical microservices example....219

Conclusion....229

Points to remember....230

Multiple choice questions....230

Answers....233

References....233

11. Quarkus and Domain-driven Design....235

Introduction....235

Structure....235

Technical requirements....236

Objectives....236

Quarkus, Jakarta EE, and MicroProfile integration....236

Quarkus in action....238

Creating and setting up a new project....239

Configuring the database integration....239

Panache entity and resource code generation....240

Validating the application's behavior....241

Using Active Record with Panache....242

Using the Repository pattern with Panache....246

Using Panache from a DDD perspective....251

Conclusion....253

Points to remember....253

Multiple choice questions....254

Answers....256

References....257

12. Code Design and Best Practices for DDD....258

Introduction....258

Structure....259

Objectives....259

Anemic model vs. rich model....259

Fluent API vs. Builder pattern in DDD....264

Exception handling and logging in DDD....268

Defining the exceptions hierarchy....268

Creating trackable exception messages....270

Handling exceptions and logs securely....270

Long-term code quality and sustainability....274

Conclusion....276

Points to remember....277

Multiple choice questions....278

Answers....281

References....281

13. Final Considerations....282

Introduction....282

Structure....282

Technical requirements....283

Objectives....283

Introduction to domain storytelling....283

Purpose and benefits of domain storytelling....284

Differences between domain storytelling and agile brainstorming....285

Exploring domain storytelling....287

Further reading and continued exploration....292

Conclusion....292

Points to remember....293

References....294

Index....295

Domain-driven Design (DDD) continues to shape how modern software systems are built by bridging the gap between technical teams and business needs. Its emphasis on modeling the domain with precision and clarity is especially relevant in today’s fast-paced, complex software landscape.

This book begins with DDD fundamentals, including core principles, a shared language, and the distinction between strategic and tactical approaches, progressing to strategic concepts like bounded contexts, context mapping, and domain events. It explores the tactical Java implementation detailing entities, value objects, services, aggregates, and repositories. The book also explores testing strategies and architectural validation using ArchUnit/jMolecules. Further, it explores DDD across microservices, monoliths, and distributed systems, integrating with Clean Architecture and SQL/NoSQL data modeling to prevent impedance mismatch. It thoroughly covers applying DDD within Jakarta EE, Spring, Eclipse MicroProfile, and Quarkus.

By the end, you will be equipped to model business logic more effectively, design systems that reflect real-world domains, and integrate DDD seamlessly into enterprise applications. You will gain clarity, confidence, and the tools needed to build software that delivers business value.

What you will learn

• Apply DDD from strategic to tactical design.
• Model aggregates, entities, and value objects in Java.
• Use DDD in monoliths, microservices, and distributed systems.
• Integrate DDD with Spring and Jakarta EE frameworks.
• Apply Clean Architecture principles alongside DDD.
• Structure data modeling for SQL and NoSQL systems.
• Apply bounded contexts, context mapping, and domain events for architecture.
• Unit/integration testing, validate design with ArchUnit/jMolecules.
• Build responsive microservices with Quarkus extensions, reactive programming.

Who this book is for

This book is ideal for Java developers, software architects, tech leads, and backend engineers. It is especially valuable for professionals designing scalable enterprise systems or applying DDD in modern software architecture.