ClassCastException in Hibernate 6 when "join fetch" is used in a query with entity inheritance

Description

em.createQuery("select e from " + Entity1.class.getSimpleName() + " e left join fetch e.subClass1 left join fetch e.subClass2 ", Entity1.class).getSingleResult()

This query used to work in Hibernate 5, but I'm getting the following error in Hibernate 6:

Exception in thread "main" java.lang.ClassCastException: class org.example.entity.SubClass1 cannot be cast to class org.example.entity.SubClass2 (org.example.entity.SubClass1 and org.example.entity.SubClass2 are in unnamed module of loader 'app')

@Entity
@Getter
@Setter
public class Entity1 {
    @Id
    String id;

    @OneToOne(fetch = FetchType.LAZY, mappedBy = "entity1")
    protected SubClass1 subClass1;

    @OneToOne(fetch = FetchType.LAZY, mappedBy = "entity1")
    protected SubClass2 subClass2;
}

@Entity
@Getter
@Setter
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class SuperClass implements Serializable {
    @Id
    public String id;

    @ManyToOne
    protected Entity1 entity1;
}

@Entity
@DiscriminatorValue("1")
public class SubClass1 extends SuperClass {
}

@Entity
@DiscriminatorValue("2")
public class SubClass2 extends SuperClass {
}

Attachments

14 Jun 2023, 04:02 PM

Linked issues

relates to

HHH-16494

Right or full joining on single tablepolymorphic entities gives incorrect results

Activity

Show:

Seong Lee August 8, 2023 at 7:00 PM

Hello, i’m also in a similar situation and it is not working on 6.2.6.Final or 6.3.0.CR1.

Posted my case in a comment here: https://hibernate.atlassian.net/browse/HHH-16934?focusedCommentId=112562

Victor Mariano Lessa de Assis July 31, 2023 at 10:19 AM

Tested with version 6.3.0.CR1 and got the same error message as before.

Marco Belladelli July 31, 2023 at 7:29 AM

Hello @Victor Mariano Lessa de Assis, since https://hibernate.atlassian.net/browse/HHH-16494 was merged it would be nice if you could test if your issue persist with the latest version of Hibernate 6.3.0.CR1 that includes that fix.

Marco Belladelli June 20, 2023 at 2:59 PM

This might be related to https://hibernate.atlassian.net/browse/HHH-16494, as that issue is meant to address implicitly treated joins (i.e. that use subtypes without an explicit treat in the query) correctly.