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 Power of Constructors

The preceding input model, SendMoneyCommand, puts a lot of responsibility on its constructor. Since the class is immutable, the constructor's argument list contains a parameter for each attribute of the class. And since the constructor also validates the parameters, it's not possible to create an object with an invalid state.

In our case, the constructor has only three parameters. What if we had more parameters? Couldn't we use the Builder pattern to make it more convenient to use? We could make the constructor with the long parameter list private and hide the call to it in the build() method of our builder. Then, instead of having to call a constructor with 20 parameters, we could build an object like this:

new SendMoneyCommandBuilder()

    .sourceAccountId(new AccountId(41L))

    .targetAccountId(new AccountId(42L))

    // ... initialize many other fields


We could...