Hibernate mapping inheritance

Question

I have a class ClassA mapped to TableA. I also have a mapping for it and it has an entity-name of EntityA.

Now, I need to create another mapping named EntityATwo between ClassA for TableA, but slightly different.

Although I could copy-paste the mapping of EntityA to EntityATwo, it would be very difficult to maintain that.

Thus, my question is, how do I create the mapping for EntityATwo wherein I declare there only what is different between EntityATwo and EntityA, while the rest of the mappings are derived from EntityA.

Thanks, Franz

Answer 1

I don't know a way to do that directly. But with your permission, I might elaborate.

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In our code, we usually like to have one java class map to one semantic (we prefer to work with compile-checked class than unchecked Strings). Therefore, instead of mapping twice the class to the table with different entity names, we would map two classes. We would have :

• ClassA as the common superclass, with most mapping that is common. It is declared (in hbm.xml) with all this mapping.
• ClassA1 extends ClassA, provide its unique mapping (and java code if needed, otherwise it could be empty). It inherits the common mapping from ClassA.
• ClassA2 also

You don't have duplication anymore. And you gain something on semantics.

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Another possibility is to use annotations on the java class, only for the common mapping. In Hibernate, Annotations can be overriden (or completed) by xml mappings. So I guess you could override only the relevant part in xml, and you would have no duplication.