Looking for inspiration on how to build a web application with a clean, maintainable architecture can be frustrating. Many web sources and books do a great job of explaining the concepts of a clean architecture, but fall short in giving hands-on advice on how to implement them.

This book fills this void by converting the concepts of a Hexagonal Architecture into actual code. It concentrates on one of the most common forms of applications we're building today - a web application with an underlying database.

The book starts with a discussion about the conventional layered architecture style and which advantages the domain-centric architecture styles of Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture bring to the table. It then quickly dives into hands-on chapters that show a way of how to manifest a Hexagonal Architecture in actual code.

After discussing each of the layers in a hexagonal architecture style, the book goes into detail about different mapping strategies between those layers, how to assemble the architecture elements to an application, how to enforce the architecture boundaries, which shortcuts produce which technical debt, and when we might willingly take on this technical debt anyways.

Table of Contents

1. What’s Wrong With Layers?

2. Inverting Dependencies

3. Organizing Code

4. Implementing a Use Case

5. Implementing a Web Adapter

6. Implementing a Persistence Adapter

7. Testing Architecture Elements

8. Mapping Between Boundaries

9. Assembling the Application

10. Enforcing Architecture Boundaries

11. Taking Shortcuts Consciously

12. Deciding on an Architecture Style

About the Author

Tom Hombergs is a software engineer by profession and by passion with more than a decade of experience in many different software projects for many different clients across various industries. In software projects, he takes on the roles of software developer, architect and coach, with a focus on the Java ecosystem.

He found that writing is the best way to learn, so he likes to dive deep into topics he encounters in his software projects to create texts that give structure to the chaotic world of software development. He regularly writes about software development on his blog at reflectoring.io and is an occasional speaker at conferences.