Implementing a Use Case

Let's finally look at how we can manifest the architecture we have discussed in actual code.

Since the application, web, and persistence layers are so loosely coupled in our architecture, we are totally free to model our domain code as we see fit. We can do DDD, we can implement a rich or an anemic domain model, or we can invent our own way of doing things.

This chapter describes an opinionated way of implementing use cases within the hexagonal architecture style that we have introduced in the previous chapters.

As is fitting for a domain-centric architecture, we will start with a domain entity and then build a use case around it.

Implementing the Domain Model

We want to implement the use case of sending money from one account to another. One way to model this in object-oriented fashion is to create an Account entity that allows us to withdraw and deposit money so that we can withdraw money from the source account and deposit it into the target...