@ManyToOne mappedBy not allowed?

[mazz]

I'm sure there is a very good reason for this, I was hoping someone can fill me in.

Why doesn't the specification allow me to specify "mappedBy" in the @ManyToOne relationship annotation?

Suppose I have Individual and Family entities - a ManyToOne. Family has the OneToMany annotation and Individual has the ManyToOne annotation. If I want the bi-directional relationship to be owned by Family - I can't - the mappedBy isn't allowed in the ManyToOne annotation that I put in Individual.

I'm sure I just don't understand this 100%... looking for an idiot lesson :-)

I guess a definition of "owns a relationship" is probably in order... what does it mean when something "owns a relationship"?

[tsar_bomba]

I'm very new to EJB3 but have not had a problem doing stuff like this so far, so bear with me.

If you used a mappedBy on your OneToMany to the field in the ManyToOne class...the relationship should be automatic (implied)....otherwise you could use a @JoinColumn annotation to specify the field, if you must.

See here:

http://docs.jboss.org/ejb3/app-server/HibernateAnnotations/reference/en/html_single/index.html#d0e1018

[mazz]

Thanks for pointing out that URL. I did find the exact answer to my question there:

http://docs.jboss.org/ejb3/app-server/HibernateAnnotations/reference/en/html_single/index.html#entity-mapping-association-collections

Section 2.2.5.3.2.1 answers the question directly:

Since many to one are (almost) always the owner side of a bidirectional relationship in the EJB3 spec, the one to many association is annotated by @OneToMany( mappedBy=... )

...

To map a bidirectional one to many, with the one-to-many side as the owning side, you have to remove the mappedBy element and set the many to one @JoinColumn as insertable and updatable to false. This solution is obviously not optimized from the number of needed statements.