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From "Fay Wang (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-782) Support for collections of embeddables and basic types
Date Mon, 24 Nov 2008 23:57:44 GMT
Support for collections of embeddables and basic types
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                 Key: OPENJPA-782
                 URL: https://issues.apache.org/jira/browse/OPENJPA-782
             Project: OpenJPA
          Issue Type: Question
            Reporter: Fay Wang
            Assignee: Fay Wang


Regarding jpa 2.0 embeddable, suppose Entity A contains a collection of embeddables.
The collection of embeddable is stored in a separate table. @CollectionTable can be used to
specify the table name, etc. If the @CollectionTable is not used, a default table name is
used (see spec, p 272 ). 

The embeddable may contain the relation to EntityB in the following scenarios:
(1) If in the embeddable, there is:
      @ManyToOne
       private EnittyB entityB; 
   
       then the relation from EntityA to EntityB is OneToMany, 
       and the relation from EntityB to EntityA is ManyToOne (Spec 2.5):
       @ManyToOne
       private EntityA entityA;

(2) If in the embeddable, there is:
      @OneToOne
      private EntityB; 

      then the relation from EntityA to EntityB is OneToMany,
      and the relation from EntityB to EntityA is ManyToOne (Spec 2.5):
      @ManyToOne
      private EntityA entityA;

(3) If in the embeddable, there is:
      @OneToOne(mappedBy = "entityB")
       private EntityB
       The relation from EntityA to EnityB is OneToMany,
       and the relation from EntityB to EntityA is ManyToOne:
       @ManyToOne
       private EntityA entityA;       

The relation to EntityB will be stored in the third table (the CollectionTable) so that it
can be associated with the embeddable. However, we can not use "mappedBy" in the ManyToOne
relation in EntityB. How to have bi-directional relation between EntityA and EntityB in these
situations? Is it possible to have a bi-directional relation between these two entities when
embeddable is involved as described above?

In scenario (3), an explicit "mappedBy" is specified in the embeddable, so that the bi-directional
relation between EntityA and EntityB will be stored in the EntityB table, but then how can
we associate EntityB with the embeddable when EntityA is retrieved back as embeddable itself
does not have identity?












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