The last I used Java's integration to RPG, specifically PCML, I made some good progress but then was stopped by a brick wall. The brick wall was a limitation on the number of parameters that could be passed (i.e. seven parms max at the time), the lack of being able to pass date data types, and the lack of being able to pass back anything other than an int in the passback parm of an RPG sub procedure.
Forgive my ignorance... but what's the point of PCML? Why not simply call an RPG service program as a native method? Or use SQL and make it a UDF? Or a stored procedure?
What advantage does PCML provide?