Automatic UML diagrams are not going to be very helpful from existing java source code. You are going to notice that the code is a big mess where the Single Responsibility Principle is not applied consistently. Take a look at inFusion to get some better views on your code. It can export a Famix model for use with Moose. That you can program to get the exact views you currently need.
Do you already have Sonar installed? It provides static views on the code.
