I have the following classes:




I get the expected polymorphic behavior when I load these types directly. That is, if I load all entities of type A, then I only get type A, or if I load all entities of type B, then I only get type B.

If I have an association collection of type A in another entity, then I do not get the polymorphic behavior that I would expect. That is, if I have the following class defined:



If I load a class of type Container, then its associated collection of A contains entities of type A and type B whereas I expect only A. Can anyone tell me how I have misconfigured my entities to get the behavior I am seeing rather than what I am expecting?

Thanks in advance,
-Anthony

For what you want, you need to set the B type with @Entity(polymorphism = PolymorphismType.EXPLICIT)

Regards,
Pavol

I tried your suggestion but to no avail. I annotated class B as having polymorphism type explicit but it had no effect. I have now tried the following combinations:

1. class A = polymorphism.explicit, class B is none
2. class A = polymorphic.explicit, class B = polymorphism.explicit
3. class A = none, class B = polymorphism.explicit

No combination has the desired effect of having a collection of only type A in a container entity.

Any other ideas? Is there no way to get the behavior I need?

Thanks,
Anthony

Maybe ugly solution, but you can try the @Where clause and just select the A class according discriminator?

Pavol

Could you point me in the direction of some documentation that describes how to use the @Where clause to discriminate based on class type? I can't seem to find anything that describes how to do it.

Thanks,
Anthony

Never tried, but you can use the annotations to set the discriminator like:

@DiscriminatorColumn(name="DTYPE", DiscriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue("CLASSA")
class A

It is a standard col, and use it in Where as DTYPE = CLASSA ..

I don't know however, if you are using JPA (this annotations are JPA ones) or just pure hibernate.

but, an ugly solution as I said. Try to find out why the explicit does not work.

Pavol

I would rather not put that discriminator on as there may be more types in the future, and that solution is not so flexible.

I can't figure out why the polymorphism setting isn't working. It seems to always issue two sql requests, one for each type. However, it only issues those two requests for the collection of the base type in the container, and never for direct loads of the respective types.

To do this, you can't use JOINED as in the original suggestion because the discriminator is ignored for this strategy. The suggestion is to use a SINGLE_TABLE strategy with SecondaryTables for the subclass (http://opensource.atlassian.com/projects/hibernate/browse/ANN-562)

I was trying to use PolymorphismType for this problem as well, but it seems that it just doesn't work that way by design:
http://opensource.atlassian.com/projects/hibernate/browse/ANN-314
...which is a pity. InheritanceType.JOINED + PolymorphismType.EXPLICIT + discriminators would solve my problem nicely.

-Eoin

[url][/url]