How can I override an EJB 3 session bean method with a generic argument - if possible at all?

Question

Suppose you have the following EJB 3 interfaces/classes:

public interface Repository<E>
{
   public void delete(E entity);
}

public abstract class AbstractRepository<E> 
   implements
   Repository<E>
{
   public void delete(E entity){
      //...
   }
}

public interface FooRepository<Foo>
{
   //other methods
}

@Local(FooRepository.class)
@Stateless
public class FooRepositoryImpl
    extends
    AbstractRepository<Foo> implements FooRepository
{
   @Override
   public void delete(Foo entity){
      //do something before deleting the entity
      super.delete(entity);
   }

   //other methods

}

And then another bean that accesses the FooRepository bean:

//...

@EJB
private FooRepository fooRepository;

public void someMethod(Foo foo)
{
    fooRepository.delete(foo);
}

//...

However, the overriding method is never executed when the delete method of the FooRepository bean is called. Instead, only the implementation of the delete method that is defined in AbstractRepository is executed. What am I doing wrong or is it simply a limitation of Java/EJB 3 that generics and inheritance don't play well together yet?

Answer 1

Can you write a unit test against your FooRepository class just using it as a POJO. If that works as expected then I'm not familiar with any reason why it would function differently inside a container.

I suspect there is something else going on and it will probably be easier to debug if you test it as a POJO.

Answer 2

I tried it with a pojo and it seems to work. I had to modify your code a bit. I think your interfaces were a bit off, but I'm not sure.

I assumed "Foo" was a concrete type, but if not I can do some more testing for you.

I just wrote a main method to test this. I hope this helps!

public static void main(String[] args){
     FooRepository fooRepository = new FooRepositoryImpl();
     fooRepository.delete(new Foo("Bar"));
}

public class Foo
{
    private String value;

    public Foo(String inValue){
     super();
     value = inValue;
    }
    public String toString(){
     return value;
    }
}

public interface Repository<E>
{
    public void delete(E entity);
}

public interface FooRepository extends Repository<Foo>
{
    //other methods
}

public class AbstractRespository<E> implements Repository<E>
{
    public void delete(E entity){
     System.out.println("Delete-" + entity.toString());
    }
}

public class FooRepositoryImpl extends AbstractRespository<Foo> implements FooRepository
{
     @Override
       public void delete(Foo entity){
          //do something before deleting the entity
       System.out.println("something before");
          super.delete(entity);
       }
}

Answer 3

Today it worked without changing any line of code. So something else must have gone wrong with the runtime environment, the debugger or something... Thanks for your answers!