Question

I’m extending an entity which doesn’t auto generate its id.

I want to ‘override’ its generation strategy to AUTO in my derived class.

Something like this.

@Entity
public class Base {

    @Id
    @Column(name = "id")
    public Integer getId() {
      return id;
    }

}

@Entity
public class Extender extends Base {

    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer getId() {
        return super.getId();
    }
}

This is what I get when I try to do it:

Caused by: org.hibernate.MappingException: Repeated column in mapping for entity: Extender column: id (should be mapped with insert="false" update="false")

I understand why this happens, but I need to know if there is a valid way to do it.

Thanks,

Answer 1

It is impossible, because you can define primary key only once and GeneratedValue can be only where primary key is defined. And same with words from specification:

2.4 Primary Keys and Entity Identity
… The primary key must be defined exactly once in an entity hierarchy.

11.1.17 GeneratedValue Annotation
… The GeneratedValue annotation may be applied to a primary key property or field of an entity or mapped superclass in conjunction with the Id annotation.