Hibernate version:
3.2

I'm trying to use @MappedSuperclass for java inheritance (there's no polymorphism, just several classes each in their own table, but with common fields/code). I'm using annotations, and one of the fields (user) is not nullable in the superclass, because the majority of implementations don't want a null, but in one sub-class, it does want to allow null.

The superclass says:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "user_id", nullable = false)
public User getUser() {...}

I've annotated that SubClass as
@AttributeOverride(name = "user", column = @Column(name = "user_id", nullable = true))

Unfortunately I get the exception:

not-null property references a null or transient value: Subclass.user
at org.hibernate.engine.Nullability.checkNullability(Nullability.java:72)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:290)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:181)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:121)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:187)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:172)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:535)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)
at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:642)


Am I doing something wrong, or is this a bug?

Even if this post is stone old, I wanna leave this information here for the next person searching for @AttributeOverride and @JoinColumn.

Solution: To override the association columns you can use @AssociationOverride

see http://www.hibernate.org/hib_docs/annotations/reference/en/html_single/