how to determine the real type of a generic property?

[Geronimo M. Hernandez]

Hello,

I have a concrete class, which is a child of a generic class. That generic class is a bean with a generic propery (I simplified the classes for sample use):

abstract class Base<T extends Object> {
   private T elem;

   public T getElem() { return elem; }

   public void setElem(T var) { elem = var; }
}

The concrete class looks like

class Derived extends Base<Integer> {
   ...
}

From a beanprocessor I like to determine the type of the "elem" property used at the concrete type "Derived".
How can I figure that out?
Using reflection, the return-type of getElem() is Object.

Any hint is welcome.

regards Gero

[Rob Spoor]

You can't, because of type erasure. In short, generics are a compile time only mechanism, and all traces of it are removed from the generated byte code.

How I solved this once is by giving the abstract class an abstract method:

abstract class Base<T extends Object> {   
    private T elem;   
  
    public T getElem() { return elem; }   
  
    public void setElem(T var) { elem = var; }   

    public abstract Class<T> getType();
}   

class Derived extends Base<Integer> {   
    @Override
    public Class<Integer> getType() { return Integer.class; }
} 

Not the most ideal solution though, because you have to override this method in all concrete subclasses. Moreso, the following provides a problem:

class Derived<T extends Number> extends Base<T> {
    @Override
    public Class<T> getType() { return ??? }
}

[Geronimo M. Hernandez]

Thank you for your support!

I will implement that getType().