Book Image

Get Your Hands Dirty on Clean Architecture

By : Tom Hombergs
Book Image

Get Your Hands Dirty on Clean Architecture

By: Tom Hombergs

Overview of this book

Building for maintainability is key to keeping development costs low and processes easy. The second edition of Get Your Hands Dirty on Clean Architecture is here to equip you with the essential skills and knowledge to build maintainable software. With this comprehensive guide, you’ll explore the drawbacks of conventional layered architecture and the advantages of domain-centric styles such as Robert C. Martin's Clean Architecture and Alistair Cockburn's Hexagonal Architecture. Then, you’ll dive into hands-on explanations on how to convert hexagonal architecture into actual code. You'll learn in detail about different mapping strategies between the layers of hexagonal architecture and discover how to assemble the architectural elements into an application. Additionally, you’ll understand how to enforce architecture boundaries, which shortcuts produce what types of technical debt, and how, sometimes, it is a good idea to willingly take on those debts. By the end of this second edition, you'll be armed with a deep understanding of the hexagonal architecture style and be ready to create maintainable web applications that save money and time.
Table of Contents (13 chapters)

The Role of Dependency Injection

The package structure described previously goes a long way toward a clean architecture, but an essential requirement of such an architecture is that the application layer does not have dependencies on the incoming and outgoing adapters, as we learned in Chapter 2, Inverting Dependencies.

For incoming adapters, such as our web adapter, this is easy, since the control flow points in the same direction as the dependency between the adapter and domain code. The adapter simply calls the service within the application layer. In order to clearly demarcate the entry points to our application, we might want to hide the actual services between port interfaces, nonetheless.

For outgoing adapters, such as our persistence adapter, we have to make use of the Dependency Inversion Principle to turn the dependency against the direction of the control flow.

We have already seen how that works. We create an interface within the application layer that is implemented by a class...