I have been evaluating yDoc which is a nice tool for generating jpg/svg UML object/class diagrams into the Javadoc process of a build phase. Its a great tool and I will be buying a copy.
The issue I had is that the ant javadoc tag doesn't seem to honor the cruise headless command detailed earlier. After a little more searching through the javadocs for doclets I have found that you can achieve the same thing with the following tag entry :
this passes the headless flag onto the running javadoc process.