JPA / Hibernate unidirectional one-to-one mapping with shared primary key?

Well, if a Child can only exist if there's a Parent, then there is a relationship between them. You may just not want to express in OO, but it does exist in the relational model.

Because that one needs to have a back reference to the parent from child which is not desirable Well, if a Child can only exist if there's a Parent, then there is a relationship between them. You may just not want to express in OO, but it does exist in the relational model. That said, I would say that the natural solution for this is to have a Parent in the Child.

But if you really don't want to do that, I would suggest taking a look at mapping the ID as a PK class, and share them with both classes, using an @EmbeddedId. I'm pretty sure it would solve your problem, with one exception: If I try to persist a "standalone" child (e.g. EntityManager. Persist(aChild)) I would expect a RuntimeException.

If you decide to use the @EmbeddedId approach in a PK class, I think you'll need to handle the above case as a "business rule".

1 Partenon, thanks for your answer. Are you sure that the EmbeddedId of the child would be populated after the parent's id was received from the DB sequence? – Korgen Jan 24 at 7:21.

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