I have a map in which I want the key to be a property of the object in the value. This can be done with annotation mappings i believe using the @MapKey annotation. I'm also not clear if that has to be a simple property? The property i'm interested in is a many-to-one assocation. Finally I wish to do this using xml mappings, because i have to use them. Thoughts? It seems the map-key element only supports adding a simple column to the map table.. as opposed to using a property of the map value.

Try the following mapping