当我尝试删除对象时，Hibernate：org.hibernate.WrongClassException

Question

I'm using inheritance to describe my model on JPA with hibernate, I have this classes:

@Entity
@Table(name = "evento")
@Inheritance(strategy = InheritanceType.JOINED)
public class Evento implements Serializable {

    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    @Id
    private int id;
    @Column(name = "numero")
    private String numeroEvento;

And this child class:

@Entity
@Table(name = "evento_sesion")
@PrimaryKeyJoinColumn(name = "idevento", referencedColumnName = "id")
public class EventoSesion extends Evento implements Serializable {

    @Column(name = "objeto")
    private String objeto;
...

The problem is when I try to do a "eventoFacade.remove(e)" (e is an instance of an existent object in DB) I get this error:

Caused by: javax.persistence.PersistenceException: org.hibernate.WrongClassException: Object with id: null was not of the specified subclass: entidades.Evento (class of the given object did not match class of persistent copy)

Somebody can help me or give me a clue?

Thanks :)

Answer 1

I try to give an answer, but the answer will be speculative; the problem is in the code which performs the remove on the entity manager, ie in eventoFacade.remove(e) .

However, assume that you have created and stored an Entity of type EventoSession in the database, and then you try to invoke em.remove with an instance of the base type, then you get the exception which you mentioned.

Let us assume, that the entity of type EventoSession has the primary key 1, and now we try to remove this entity.

Evento es = new Evento();
es.setNumeroEvento("...");
es.setId(1);

es = em.merge(es); // detached objects cannot be removed, therefore we merge es
em.remove(es);

The call to em.merge will then end in a javax.persistence.PersistenceException , caused by:

Caused by: org.hibernate.WrongClassException: 
    Object [id=null] was not of the specified subclass [entidades.Evento]: 
    class of the given object did not match class of persistent copy

and I assume that this could be the problem.

To fix it, simply load the instance to be removed over the entity manager:

em.remove(em.find(Evento.class, 1));