inheritence and column names

dward2 · **Posted:** Mon Nov 28, 2005 5:22 pm

If I have a base class with a property and I use an annotation to give it a column name, it seems I'm stuck with that column name for all subclasses.

With hbm.xml mapping files, I can have a base class with, say, set/getId():Long, but then map the column name separately per subclass so I can have foo_id and bar_id (same java property but different db column names).

How would I do this in ejb3? Define the id property as @Transient in the base class, then override it each the subclass with @Id and @Column? I know I could just try it, but I want to know (if it works), is it an accepted path? What do other people do?

Much thanks.

emmanuel · **Posted:** Tue Nov 29, 2005 5:39 am

@PrimaryJoinColumn for JOINED strategy
this is not possible for table per class

dgreen99 · **Joined:** Fri Dec 09, 2005 6:15 pm **Posts:** 2

I've tried overriding a @Column in a subclass, and it doesn't work. My code appears as follows:

Code:

@Entity public abstract class AuditedEntity {

   @Id(generate = GeneratorType.AUTO)
   @Basic(optional = false)
   @Column(name = "Id", nullable = false)
   public abstract Long getId();

   public abstract void setId(Long id);
}

The concrete class looks like this:

Code:

@Entity public class UserProfile {

   @Basic(optional = false)
   @Column(name = "UserId", nullable = false)
   public Long getId() { ... }

   public void setId(Long id)  { ... }
}

This code deploys fine, however it seems that Hibernate ignores the @Column annotation in the base class. Should this approach work? I haven't seen any text in the EJB3 spec. to the contrary. Is this just a limitation of Hibernate?

dgreen99 · **Joined:** Fri Dec 09, 2005 6:15 pm **Posts:** 2

Further reading of the EJB3 spec found this:

Quote:

Entity subclasses may override the property accessor methods. However, portable applications must not
override the object/relational mapping metadata that applies to the persistent fields or properties of
entity superclasses.

So it looks like the EJB3 spec says this approach is a bad idea. Too bad.