I have seen a couple of questions like this go by before, but I believe the answer(2) were incorrect.

In my situation, I have a 'business key', which I define as a component with three properties. This key is NOT the primary key, as we all know that is not good persistent OO design, but it indeed is a unique key, as a 3-tuple.

I would like to specify <component ...... unique="true">, hoping that Hibernate would translate that into a unique composite key constraint, but there is no such option available. Others on this list have suggested putting a unique attribute on each of the component's properties, but will this not merely create three disjoint unique keys? How should we declare a composite business key for non-entity type objects?

Jay

Is component required here ?

Won't a unique index be created on the two columns by virtue of the unique-key as long as the value of unique-key is same. At least II think I am getting the same results without the component tag.

aaa..h.....I get it. component refers to an external class that have the keys defined in it.

Thanks for the reply Gavin. But I am still not clear on this. Using the syntax you suggested below, isn't there TWO interpretations of how to set up constraints? How does Hibernate know from this whether I want two, seperate, disjoint unique key constraints OR whether I want a single composite key containing the first column as the primary and the second column as the secondary key? Of course those are completely different kinds of constraints - I know I can get disjoint keys set up without using a component but I am still not clear on how to get a composite key set up....

If you give the same unique-key name, they will be part of the same unique key.

DOH!!!!! Ok I get it now... thanks to all for the input.

Jay