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)

Assembling the Application

Now that we have implemented some use cases, web adapters, and persistence adapters, we need to assemble them into a working application. As discussed in Chapter 3, Organizing Code, we rely on a dependency injection mechanism to instantiate our classes and wire them together at startup. In this chapter, we will discuss some approaches for how we can do this with plain Java and the Spring and Spring Boot frameworks.

Why Even Care about Assembly?

Why aren't we just instantiating the use cases and adapters when and where we need them? Because we want to keep the code dependencies pointing in the right direction. Remember: all dependencies should point inward, toward the domain code of our application, so that the domain code doesn't have to change when something in the outer layers changes.

If a use case needs to call a persistence adapter and just instantiates it itself, we have created a code dependency in the wrong direction. This is...