Inherit generic class keeping generics and retrieve generic type in parent

Question

I have an abstract class which generics and tried to extend it passing through the generics.
But it seems that it isn't possible to get the generic type anymore.

The root class

public abstract class AbstractDataModel<T extends AbstractEntity> extends DataModel<T> {

    private final Class<T> rootType;

    protected AbstractDataModel() {
        Type genericSuperclass = getClass().getGenericSuperclass();
        ParameterizedType parameterizedType = (ParameterizedType)genericSuperclass;
        Type type = parameterizedType.getActualTypeArguments()[0];
        rootType = (Class<T>)type;
    }

The specialization

public class OwnerDataModel<T extends AbstractEntity> extends AbstractDataModel<T> {

I get an exception when casting type to Class<T>. I got

Cannot cast 'sun.reflect.generics.reflectiveObjects.TypeVariableImpl' to 'java.lang.Class'

Normally I am using the AbstractDataModel directly

dataModel = new AbstractDataModel<Entity>() {

And I want to use my OwnerDataModel like the following

dataModel = new OwnerDataModel<Entity>();

What did I miss?

Just as a warning, it looks like you are diving deep into generics, and it my experience, it has never worked out. Just when you think you have things working, you seem to always get bitten by generic erasures. So, if you could do this with less generics, I would recommend giving that another look. — pgreen2, Nov 12 '15 at 12:42
`AbstractDataModel` is an abstract class you can't instantiate — Mourad BENKDOUR, Nov 12 '15 at 12:45
Added exception message. @ControlAltDel If I don't inherit the class it works like expected. — CSchulz, Nov 12 '15 at 13:40
Possible duplicate of [Get generic type of class at runtime](http://stackoverflow.com/questions/3403909/get-generic-type-of-class-at-runtime) — px5x2, Nov 12 '15 at 14:25
@px5x2 Not really a duplicate. I am using inheritance in comparison to your posted link. — CSchulz, Nov 12 '15 at 14:49
Please see other than 2nd answer. Especially 3rd one and its comments, imo it adresses to your question. — px5x2, Nov 12 '15 at 15:04

score 0 · Answer 1 · answered Nov 12 '15 at 12:45

0

First, you don't have to write this :

public class OwnerDataModel<T extends AbstractEntity> extends AbstractDataModel<T> { ...

but this : public class OwnerDataModel extends AbstractDataModel<T> { ...

because, is included in the first by default by AbstractDataModel<T>.

Second, You can't instantiate AbstractDataModel but the class OwnerDataModel .

answered Nov 12 '15 at 12:45

bilelovitch

1,455
14
22

But T is a generic. It doesn't compile like you suggested. – CSchulz Nov 12 '15 at 13:34

Inherit generic class keeping generics and retrieve generic type in parent

1 Answers1