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)

Post-Compile Checks

As soon as we use the public modifier on a class, the compiler will let any other class use it, even if the direction of the dependency points in the wrong direction according to our architecture. Since the compiler won't help us out in these cases, we have to find other means to check that the dependency rule isn't violated.

One way is to introduce post-compile checks – that is, checks that are conducted at runtime when the code has already been compiled. Such runtime checks are best run during automated tests within a continuous integration build.

A tool that supports this kind of check for Java is ArchUnit ( Among other things, ArchUnit provides an API to check whether dependencies point in the expected direction. If it finds a violation, it will throw an exception. It's best run from within a test based on a unit testing framework such as JUnit, making the test fail in the event of a dependency violation.

With ArchUnit...