Implementing a Web Adapter
Most applications today have some kind of web interface – either a UI that we can interact with via a web browser or an HTTP API that other systems can call to interact with our application.
In our target architecture, all communication with the outside world goes through adapters. So, let's discuss how we can implement an adapter that provides such a web interface.
Dependency Inversion
The following figure gives a zoomed-in view of the architectural elements that are relevant to our discussion of a web adapter—the adapter itself and the ports through which it interacts with our application core:
Figure 5.1: An incoming adapter talks to the application layer through dedicated incoming ports, which are interfaces implemented by the application services
The web adapter is a "driving" or "incoming" adapter. It takes requests from the outside and translates them into calls to our application...
