I think with automating Java applications, the standard approach is to inject your own robot implementation of the toolkit into the classpath, and then to access the elements of that robot toolkit.

I'm unaware of such a toolkit, and even less aware of such a toolkit that also exports an interface that can be conveniently queried from the outside, for example using a TCP socket. So I guess you have to do screen-scraping using VNC or Win32::Screenshot to get at data, and send mouse clicks and keystrokes to drive the application.