I have a class which has a many-to-one polymorphic association e.g. we have OrderItem which links to Product which has MusicProduct and FilmProduct as subclasses.

Can I issue an HQL query that returns OrderItems that refer to only MusicProduct.

Had a look on the Hibernate forum, but only found unanswered questions.

TIA

hmm, something like "from OrderItem oi where oi.Product.class = Fully.Qualified.MusicProduct" maybe?

Get's me half way there as I also need to restrict on properties that only exist on the subclass.

Think I've got it, but I don't know how general this is; this should retreive and order that contains a MusicalProduct...

select item.Order
from OrderItem item, MusicProduct mp
where item.Product = mp
and mp.IsrcCode = 'Fred'

You have to introduce the subclass explicitly as there doesn't seem to be a way of casting it to the subclass in HQL.

Actually, I'm interested to know whether anyone knows more about this - is there a way to doing casting to a subclass in a query so that a property from a derived class can be included? Or is it absolutely required to do it the way paulh has described?