Annotation Arguments with Generics Class

Question

I would like to understand of this issue

public class DogController extends FeedCommonController<DogModel extends CommonAnimalModel, FARMER_1_AUTH> {
  // something

 // This is working - but there is duplication
  @Security.Authenticated(FARMER_1_AUTH.class)
  public boolean feed_it() {
    // nothing special
    DogModel.getRandom().feed_it();
  }
}

public class CatController extends FeedCommonController<CatModel extends CommonAnimalModel, FARMER_2_AUTH> {
  // something

  // This is working - but there is duplication 
  @Security.Authenticated(FARMER_2_AUTH.class)
  public boolean feed_it() {
    // nothing special
     CatModel.getRandom().feed_it();
  }
}

And I want to simplify the code and remove the duplicate methods, but I cannot put Class type to annotation.

public abstract class CommonAnimalController< T extends CommonAnimalModel, XXXXXX> {

   @Security.Authenticated(XXXXXX.class) // <-- Here is a problem with declaration 
   public boolean feed_it() {
      T.getRandom().feed_it();
   }

}

/**
Get Token From HTTP Request from Actual Thread
*/
public class Security {

  @With(AuthenticatedAction.class)
  @Target({ElementType.TYPE, ElementType.METHOD})
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Authenticated {
    Class<? extends Authenticator> value() default Authenticator.class;
  }

}

Concept with Annotation is already created and implemented on hundred classes. So its not possible make huge changes. But Its some Elegant way how to solved this?

since you are sharing the code, make it simple, share everything for a compilable code. Are missing the mdoels. DogModel, etc. Possibly all in a single code place so one can copy paste your code and check deeper. — Ermal, Nov 23 '19 at 16:41
ITs Simple code, and its not question about compilation.. but about how to design the code and what patterns to use. — TyZet, Nov 23 '19 at 17:47

Ermal · Answer 1 · 2019-11-23T18:04:52.310

You have two problems in one question.
First problem you have is: How to get a class instance of generics type T
This is answered here: How to get a class instance of generics type T

The second problem you have, is how to avoid passing a constant to the annotation.
You will have a compliation error "Attribute value must be constant"
For this second problem seems there is no simple way to achieve it in Java. (pheraps I am wrong)
See this answer: How to supply value to an annotation from a Constant java

Solution for problem1

public abstract class CommonAnimalController<T extends CommonAnimalModel, XXXXXX> {
    final Class<XXXXXX> typeParameterClass;

    public CommonAnimalController(Class<XXXXXX> typeParameterClass) {
        this.typeParameterClass = typeParameterClass;
    }
    @Security.Authenticated(typeParameterClass)  // you will have "Attribute value must be constant"
    public boolean feed_it() {
        return T.getRandom().feed_it();
    }
}

Annotation Arguments with Generics Class

1 Answers1