jpa - JPAでCriteriaポリモーフィック結合を行うにはどうすればよいですか?

Question

次のようなモデリングを持つプロジェクトがあります。

public abstract class Actor{}
public class Person extends Actor {}
public class Organization extends Actor {}

public abstract class Role{ @ManyToOne @JoinColumn(name="ID_ACTOR") }
public class Customer extends Role{}
public class Employee extends Role{}

List<Role>特定のアクターを演じるを取得したいと思います:

public List<Role> getRoles(Actor actor) {
  CriteriaBuilder builder = em.getCriteriaBuilder();
  CriteriaQuery<Role> criteria = builder.createQuery(Role.class);

  //How to do this filter using Criteria API (JPA 2.1)?

  return query.getResultList();
}

以下のSQLは仕事をします：

SELECT 'Customer' as role, c.id as id, c.id_actor as actor
FROM customer c
left join person p on p.id = c.id_actor
left join organization o on o.id = c.id_actor
where c.id_actor = ?

UNION 

SELECT 'Employee' as role, e.id as id, e.id_actor as actor
FROM employee e
left join person p on p.id = e.id_actor
left join organization o on o.id = e.id_actor
where e.id_actor = ?