Question

I have the following

@MappedSuperclass
public abstract class A {
    @Id @GeneratedValue
    public Long id;
}

@Entity
public class B extends A {
}

@Entity
public class C extends A {
}

@Entity
public class D {
    @ManyToOne
    public A a;
}

The problem is class D and the field a (could be either of type B or C). What should be the mapping?

Answer 1

If you reference an A from another entity, then A should not be a MappedSuperclass, but an entity. You should annotate it with @Entity, and choose an inheritance strategy.

Other than that, the mapping will stay as is.