Discover Hexagonal Architecture to create web applications with isolated, testable layers. Gain insights into designing clean, maintainable modules and advocating for suitable techniques for your application.

Get Your Hands Dirty on Clean Architecture by Tom Hombergs.png

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This course will teach you all about creating a web application in the Hexagonal Architecture style. Hexagonal Architecture promotes the separation of concerns by encapsulating logic in different layers of the application. This enables a higher level of isolation, testability, and control over your business specific code. 

You will learn how to design software modules and complete applications in a clean and maintainable manner, while also learning how to advocate for a certain technique given your application and constraints.

By the end of this course, you will have a greater understanding of how to implement software architecture, a key skill for any senior developer.

Hexagonal Software Architecture for Web Applications

While validating input is not a responsibility of a use case class,  it belongs in 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 one might get it wrong or forget it altogether.



The application layer should care about input validation because if it does not, it might get invalid input from outside the application core. This might cause damage to the state of our model.

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

# Creating the `SendMoneyCommand`  class

We'll let the *input model* take care of it. For the "Send Money" use case, the input model is the `SendMoneyCommand` class we have already seen in the previous code example. More precisely, we'll do it within the constructor:

Before We Begin

What's Wrong with Layers?

Inverting Dependencies

Organizing Code

Implementing a Use Case

Implementing a Web Adapter

Implementing a Persistence Adapter

Testing Architecture Elements

Mapping Between Boundaries

Assembling the Application

Enforcing Architecture Boundaries

Taking Shortcuts Consciously

Assessment

Conclusion

Appendix

Validating Input