We tried to do it only with Robot Framework and the available Libraries.
I understood that this one could theoretically be used to automate Java SWT Applications:
But we didn’t succeed.
In the end, we combined Robot Framework with a Commercial Tool QF Test that offers a Robot Framework Library
So in the end, we used the steering engine (for Java SWT) from that Tool, but wrote our tests and keywords in Robot Framework syntax.
Maybe that approach is also a possibility for you