I've looked and looked and cannot find any docs on how to form queries with composite keys. Could someone point me in the correct direction? In particular, I'd like to do a Select distinct on an class that has a composite key.

TIA,

You need to use the id.field for the fields of the composite Key.

what about doing something like this:
String query = "from com.test.myComposedIdClass c where c.id1= :id1 and c.id2 = :id2"

It looks too easy, sure i've misunderstood your problem

Excuse:
String query = "select distinct(c) from com.test.myComposedIdClass c where c.id1= :id1 and c.id2 = :id2"

In the end, this is what worked:

Collection list = session
.createQuery("select distinct location.comp_id.lsecurityId from Location as location").list();

The reason for makening it return a list is that it cannot return entity objects just string containing the name of the unique properity