I'm having problems mapping Generics in Hibernate. Our database tables are all designed the same way and each table has an identifier with ID and DATE. ID can be an Integer or a String. I created a generic class, which can accept Integer or String as valid types for the ID-field.

So far so good. However, Hibernate doesn't know the type of object when he parses the mapping file. I've done some debugging and apparently it compares the amount of columns from the mapping file to the number of fields in the corresponding object (somewhere in RootClass). When it encounters an object of type java.lang.Object, it returns a column span of 2 by default (I think it was in SimpleValue.class). Javadoc states that this is because Object is deprecated (don't know why, but ok). So the columnspan is not equal and I get an exception:



Is there a way to map a composite-id with generics? And how to do it? Or how to map a variable of type java.lang.Object?

I think Hibernate must know the exact object type when you start the session.
So, perhaps the best way to implement that you want is to create a custom hibernate type.
Another easy solution I propose you is to store all as a String, so hibernate know the exact object type. Then you can add several getters and setters for integers and String, something like:



I havnt compiled the code, is only a suggestion.
hope this help

We've been upgrading to Hibernate 3, but the problem persists unfortunately :). Maybe a bit gullible :p.

We'll implement a workaround, but what I still don't understand is why ObjectType (or AnyType as of 3) returns a column span of 2 by default. Javadoc doesn't say a thing and documentation stays quiet about this one. Hopefully someone around here can explain this :).