[#HHH-1152] Value object(<component>) inheritance mapping

Hibernate Core

Value object(<component>) inheritance mapping

Created: 13/Nov/05 01:08 AM Updated: 07/Nov/08 09:01 AM

Component/s:

core

Affects Version/s:

3.1 beta 2

Fix Version/s:

None

Time Tracking:

Not Specified

Issue Links:

Prerequisite

This issue depends on:

HHH-1907 offload metadata information from ComponentType to SessionFactory

Description

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Though fine-grained object mapping is one of Hibernate's main objectives, it still doesn't support *value object* (<component>) inheritance mapping, only entity inheritance mapping.
It would be best if <component> tag could also contain similar tags for inheritance as entity does.

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Max Rydahl Andersen added a comment - 14/Nov/05 02:16 AM

definitly not minor and you should be able to do this with a paramaterzied compositeusertype

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Jonni Gani added a comment - 11/Jun/07 08:27 AM

Just to echo Vjeran, component inheritance similar to entity inheritance would be good, though the one I'm particularly interested in is 'Table per class hierarchy' with a discriminator column. This issue should get a higher priority as it's essential for good model design with proper distinction between Entity and Value Object.

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Ilya Boyandin added a comment - 16/Jul/08 03:34 AM

It's definitely not minor. In the absence of this feature changes have to be made to the domain model to workaround the problem.

I think it would be very easy to implement it at least for the "table per class hierarchy" strategy. Others don't necessarily have to be supported.

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Stefan Fromm added a comment - 07/Nov/08 07:07 AM

I'm trying to implement the Role Object Pattern for domain objects. I would need component inheritance for the role objects. Treating them as entities is not possible, because they appear to be the same object as their core object - they have the same identity. Adding more than 1 role object to the core object results in a NonUniqueObjectException. I have to change back my domain model to the Extension Object Pattern where the extension/role objects are not identical to their core object.

I agree with Ilya. "table per class hierarchy" would suffice initially.