The core goal of the ports & adapters architecture is to decouple the system’s business logic from its infrastructural components.

Instead of referencing and calling the infrastructural components directly, the busi‐ ness logic layer defines “ports” that have to be implemented by the infrastructure layer. The infrastructure layer implements “adapters”: concrete implementations of the ports’ interfaces for working with different technologies (see Figure 8-11).

Figure 8-11. Ports & adapters architecture

The abstract ports are resolved into concrete adapters in the infrastructure layer, either through dependency injection or by bootstrapping.

For example, here is a possible port definition and a concrete adapter for a message bus:

namespace App.BusinessLogicLayer

{

public interface IMessaging

{

void Publish(Message payload);

void Subscribe(Message type, Action callback);

}

}

namespace App.Infrastructure.Adapters

{

public class SQSBus: IMessaging { ... }

}