Play and Guice Dependency Injection with Interface

Question

I'm trying to use Play/Guice dependency injection with an interface:

public interface IService {
    Result handleRequest();
}

public Service implements IService {
    @Override
    public Result handleRequest() {
        ...
        return result;
    }
}

public class Controller {
    private final IService service;

    @Inject
    public Controller(IService service) {
        this.service = service;
    }
}

I get:

play.api.UnexpectedException: Unexpected exception[CreationException: Unable to create injector, see the following errors:

1.) No implementation for IService was bound.  

If I change the controller class to not use the interface it works fine:

public class Controller {
    private final Service service;

    @Inject
    public Controller(Service service) {
        this.service = service;
    }
}

How do I make it work with the interface so it finds the concrete Service class?

Answer 1

You can use guice annotation @ImplementedBy like this:

import com.google.inject.ImplementedBy;

@ImplementedBy(Service.class)
public interface IService {
    Result handleRequest();
}

Or u can use modules like this:

import com.google.inject.AbstractModule;

public class ServiceModule extends AbstractModule {

    protected void configure() {
        bind(IService.class).to(Service.class);
    }
}

And then register them in application.conf play.modules.enabled += "modules.ServiceModule"