Hi,

I am trying to remove the not-owning entity of a 1:1 relation. I am using JPA resp. the HibernateAnnotations implementation of JPA.

Hibernate version:
Hibernate Core 3.2.4 SP1,
Hibernate Annotation 3.3.0 GA,
Hibernate EntityManager 3.3.1 GA

Mapping documents:
@Entity
public class A {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Basic(optional=true)
@OneToOne(cascade=CascadeType.ALL)
private B b;
}

@Entity
public class B {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Basic(optional=false)
@OneToOne(mappedBy = "b")
private A a;
}

Code between em.getTransaction().begin() and em.getTransaction().commit():
b = em.find(B.class, b.getId());
a = b.getB();
b.setA(null);
em.remove(a);

Full stack trace of any exception that occurs:
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:71)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:253)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:237)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:146)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:298)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:338)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
at org.hibernate.ejb.TransactionImpl.commit(TransactionImpl.java:54)
... 20 more
Caused by: java.sql.BatchUpdateException: Cannot delete or update a parent row: a foreign key constraint fails (`database/a`, CONSTRAINT `FK` FOREIGN KEY (`b_id`) REFERENCES `b` (`id`))
at com.mysql.jdbc.PreparedStatement.executeBatchSerially(PreparedStatement.java:1237)
at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:936)
at org.apache.tomcat.dbcp.dbcp.DelegatingStatement.executeBatch(DelegatingStatement.java:294)
at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:48)
at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:246)
... 28 more


Name and version of the database you are using:
MySql 5

I would have expected that EITHER remove the only reference to an object removes the entity from database, OR that removing an entity via EntityManager.remove(B) also sets A's reference to B to null. But even when I do both in a transaction it does not work.

I assume that setting a referece to via has no effect. Perhaps Hibernate is thinking that setting a reference to null is the same as "nothing to do here". If so, can I turn that behaviour off?

I'd appreciate any comments and hints. Thanks!

Best regards,
Matt

you need to set all references to null b.setA and a.setB then remove the object through em.remove(), exaclty like you would do in a pure OO world (em.remove() replacing the garbage collector)