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)

Validating Input

Now we are talking about validating input, even though I just claimed that it's not a responsibility of a use case class. I still think, however, that it belongs to the application layer, so this is the place to discuss it.

Why not let the calling adapter validate the input before sending it to the use case? Well, do we want to trust the caller to have validated everything as is needed for the use case? Also, the use case might be called by more than one adapter, so the validation would have to be implemented by each adapter and we might get it wrong or forget it altogether.

The application layer should care about input validation because, well, otherwise it might get invalid input from outside the application core, and this might cause damage to the state of our model.

But where to put the input validation if not in the use case class?

We will let the input model take care of it. For the "Send Money" use case, the input model is the SendMoneyCommand class we...