Is the Controller in MVC considered an application service for DDD?

Question

I am applying DDD for the M part of my MVC and after some research (studying up!), I have come to the realization that I need my controller to be interacting with domain ser

Answer 1

The application layer is somewhere between the domain layer and the presentation layer. The controller is part of the presentation layer, sends commands or queries to the application layer, where the application services execute them using the services and objects of the domain model. So controllers are different from the application services, and they are probably bound to the actual communication form, e.g. HTTP. You should not call domain services from controllers directly, this might be a sign of misplaced code.

Domain Driven Design: Domain Service, Application Service

• Domain Services : Encapsulates business logic that doesn't naturally fit within a domain object, and are NOT typical CRUD operations - those would belong to a Repository.
• Application Services : Used by external consumers to talk to your system (think Web Services). If consumers need access to CRUD operations, they would be exposed here.

So your service is probably an application service and not a domain service, or some part app services, some part domain service. You should check and refactor your code. I guess after 4 years this does not matter, but I had the same thoughts by an application I am currently developing. This app might be too small to use DDD on it, so confusing controllers with app services is a sign of overengineering here.

It is an interesting question when to start add more layers. I think every app should start with some kind of domain model and adapters to connect to that domain model. So if the app is simple enough, adding more than 2 layers might be not necessary. But that's just a thought, I am not that experienced with DDD.