Java Generics. How to properly extend parameter typed class that extends Generic abstract parameter typed class

Question

I have generic abstract superclass GenericModel with method that I would like to call in children classes as follow:

public abstract class GenericModel<T extends GenericModel> {
    @Transient protected Class<T> entityClass;
    public GenericModel() {
    Class obtainedClass = getClass();
    Type genericSuperclass = null;
    for(;;) {
        genericSuperclass = obtainedClass.getGenericSuperclass();
        if(genericSuperclass instanceof ParameterizedType) {
            break;
        }
        obtainedClass = obtainedClass.getSuperclass();
    }
    ParameterizedType genericSuperclass_ = (ParameterizedType) genericSuperclass;
    entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0]));

    // some code

    public List<T> getByCreationUser_Id(Long id) {
        // method body
        return entities;
    }
}

I am extending class this class with:

public class Insurance extends GenericModel<Insurance> {
     // some code
}

And I wanna extend class: Insurance with this class as follow:

public class Liability extends Insurance {

}

and object of Liability class I would like call method: getByCreationUser_Id() and instead of list of TI would like to get List<Liability> as follow:

List<Liability> currentUserInsurances = new Liability().getByCreationUser_Id(1L);

Unfortunatelly I am getting an error:

Type mismatch: cannot convert from List<Insurance> to List<Liability>

When I will call same method on Insurance class it works, I am getting an: List<Insurance>

I've already tried declare classes as follow:

public class Insurance<T> extends GenericModel<Insurance<T>> {}
public class Liability extends Insurance<Liability> {}

But id doesn't work. Compile errors occur.

Please help.

Answer 1

You need to declare your Insurance class as,

public class Insurance<T extends Insurance> extends GenericModel<T> {}

And then, your Liability class as,

public class Liability extends Insurance<Liability> {}