Calling *SRVPGMs from JAVA - How to DEBUG?

Our biggest issue is debugging the *SRVPGM procedures.  How do we do
that?  I can't figure out where the *SRVPGM is running.  The JAVA
program prints the job info it gets, but I can't always find that job
and even if I do there is nothing useful there.  If I have the C use
printf()  I can't find the output.  Anyone know where the output goes
and how to debug this?
 
We have a JAVA program that needs to call a *SRVPGM that contains
*MODULEs written in C, CL and RPG.  Calling the C is not too bad, except
we seem to have issues passing char variables.  We've got around it so
far by just passing them as char * instead, but we have to write
wrappers for the procedures that expect plain char parameters.
 
We also seem to have found that whatever job the *SRVPGM is running in
on the iSeries does not seem to have a *LIBL.  We had to write a
procedure that calls an existing CL that sets the appropriate *LIBL.
This is mainly an issue with the RPG, since the C can specify the
library as a variable at run time.