Field level injection with Gin

Question

I'm trying to do field-level injection so I don't have to pass "models" when my controllers are instantiated, like,

UserController controller = new UserController(/*No need to pass models here*/);

However my application throws NullPointerException, here my code:

UserController.java

    public class UserController implements Controller {
        @Inject private UserModel model;
        public UserController() {
          model.doSomething(); // NullPointerException
        }
    }

ClientGinModule.java

public class ClientGinModule extends AbstractGinModule {
    @Override
    protected void configure() {
        bind(UserModel.class).in(Singleton.class);
    }
}

What could be the problem?

Answer 1

Use In Guice

UserController controller = injector.getInstance(UserController.class);

Use in Gin:

// Declare a method returning a UserController on your interface extending Ginjector
public UserController getUserController();

// When you need the controller, just call:
injector.getUserController();

to get a fully-injected controller.