Hi all,

Is anyone able to point me in the direction of more information on persisting interfaces in Hibernate/EJB3.0? I can't see them mentioned specifically in either the EJB3.0 persistance spec, or the Hibernate docs.

Hibernate talks about querying using interfaces, but I'm trying to figure out if it will support persisting fields whose types are interfaces, where the implementing class is not known a compile time.

E.g.



Lets presume there are three or more implementations of 'Item'.... can Hibernate naturally map this to a relational schema? Maybe 1 column for each possible implementing class (some JDO implementations do this). How about collections?

Thanks for your time.

Roger

Why do you think that "interface" is different from "class" from Hibernate's point of view?

(Especially when it explicitly says that there is no difference in the docs.)

Hi Gavin,

Thanks for your reply.

So I guess the answer is 'yes'... I'm interested to know how this is implemented - can you tell me how it looks in a database schema? Are there one or more columns for someItem which reference other tables? ... and for lists?

Kind regards,

Roger

Of course the Hibernate documentation covers all the ways you can map inheritance and polymorphic associations in Hibernate. Reading the docs is highly recommended.

(Perhaps you are looking for an <any> mapping. Personally I try to use <union-subclass> instead of <any>.)