Abstracting out the external system
In this section, we will consider some of the decisions we need to make when applying the hexagonal architecture approach. We’ll take a step-by-step approach to handling external systems, where we will first decide what the domain model needs, then work out the right abstractions that hide their technical details. We will consider two common external systems: web requests and database access.
Deciding what our domain model needs
The place to begin our design is with our domain model. We need to devise a suitable port for our domain model to interact with. This port has to be free from any details of our external system, and at the same time, it must answer the question of what our application needs this system for. We are creating an abstraction.
A good way to think about abstractions is to think about what would stay the same if we changed how we performed a task. Suppose we want to eat warm soup for lunch. We might warm it in a...
