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  • Hibernate - how to delete bidirectional many-to-many association

    - by slomir
    Problem: I have many-to-many association between two entities A and B. I set A entity as an owner of their relationship(inverse=true is on A's collection in b.hbm.xml). When i delete an A entity, corresponding records in join table are deleted. When i delete an B entity, corresponding records in join table are not deleted (integrity violation exception). -- Let's consider some very simple example: class A{ Set<B> bset=new HashSet<B>(); //... } class B{ Set<A> aset=new HashSet<A>(); //... } File a.hbm.xml [m-to-m mappings only]: <set name="bset" table="AB"> <key name="a_id"/> <many-to-many column="b_id" class="B"/> </set> File b.hbm.xml [m-to-m mappings only]: <set name="aset" table="AB" inverse="true"> <key name="b_id"/> <many-to-many column="a_id" class="A"/> </set> Database relations: A(id,...) B(id,...) AB(a_id,b_id) Suppose that we have some records in AB joint table. For example: AB = {(1,1),(1,2)} where AB= { (a_id , b_id) | ... ... } -- Situation 1 - works probably because A is owner of AB relationship: A a=aDao.read(1); //read A entity with id=1 aDao.delete(a); //delete 'a' entity and both relations with B-entities Situation 2 - doesn't work: B b=bDao.read(1); //read B entity with id=1 bDao.delete(b); //foreign key integrity violation On the one hand, this is somehow logical to me, because the A entity is responsible for his relation with B. But, on the other hand, it is not logical or at least it is not orm-like solution that I have to explicitly delete all records in join table where concrete B entity appears, and then to delete the B entity, as I show in situation 3: Situation 3 - works, but it is not 'elegant': B b=bDao.read(1); Set<A> aset=b.getA(); //get set with A entities Iterator i=aset.iterator(); //while removes 'b' from all related A entities //while breaks relationships on A-side of relation (A is owner) while(i.hasNext()){ A a=i.next(); a.bset.remove(b); //remove entity 'b' from related 'a' entity aDao.update(a); //key point!!! this line breaks relation in database } bDao.delete(b); //'b' is deleted because there is no related A-entities -- So, my question: is there any more convenient way to delete no-owner entity (B in my example) in bidirectional many-to-many association and all of his many-to-many relations from joint table?

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