Netbeans DataObject reference in other DataObject

Hi,
this is nothing gaming but something java related, I hope I posted in the right subforum.
I wrote a Netbeans RCP application and now I got a small problem.
A MultiDataObject that I created has a reference to an other one.
How do I save that? In the moment I simply save the path of the primary file and my LogicalView provids the possibility to get the DataObject from a file path. To be honest that seams like a dirty hack and it is one.
How am I supposed to solve that? Is there a better way?

-ClaasJG