title: Generating Hibernate composite key object from hbm file
body: <p>(Parenthetical rant:) I'm a Hibernate beginner getting slightly frustrated by the overhead of a simple join that I could write in 15 seconds in SQL. (End rant)</p>
  
  <p>The situation is thus: I have 2 tables that both contain the same composite primary key - let's call the columns in both tables 'ID' and 'Version'.  I need data about a particular ID/Version from both tables, so </p>
  
  <pre><code>select a.xxx, b.yyy 
  from tableA a, tableB b
  where a.ID = b.ID
      and a.Version = b.Version
      and .....
  </code></pre>
  
  <p>Bad table design, but not in my hands.</p>
  
  <p>In Hibernate, my online research suggests creating a separate composite key class to be shared by the tables, with an A object containing a B object, and a one-to-one mapping between them in A's hbm file.</p>
  
  <p>In my project, all my Hibernate data objects are generated with hbm files and located in the same place.  So I'd like to know if I can create this composite key object also using an hbm file and store it with its brethren.  The issue is, it doesn't map to any <em>table</em> in particular (or, you could say it maps to 2 tables).  I'm trying to determine if it's possible to create this composite key class with an hbm file, and also if it's advisable or not to do so.  Am I going about this the wrong way?</p>
  
  <p>Thanks in advance.</p>