Re: Debugging Java programs on the ISeries

I've also been to hell and back trying to debug Java programs on the AS400 
but I finally got it to work.  I was calling a Java program from RPG, and 
I wanted to debug the Java code that was being remotely called from the 
RPG.  I was using STRSRVJOB on another session so that I could remotely 
debug the Java code.  I needed to be able to debug my Java class on the 
AS400, not on a Windows box running a remote debugger.

What I found out was the following:

When you try to debug a Java class using the STRDBG command on the AS400, 
the command doesn't work unless the JVM is already running and your class 
is loaded. 

I found that I was constantly getting the error 'Java class file not 
available.' I even tried the full pathname (eg. /home/myjava.class) but it 
didn't work even though I did have my environment CLASSPATH variable set 
properly.   I pressed F1 to get a further explanation on the error and 
found out that the reason code returned was 1 for '1 - Java virtual 
machine not started.'.

Once my RPG program was loaded and had started the copy of my Java class, 
I was then able to debug the Java Code, since the JVM was now running.  I 
also learned quickly that you have to match exactly, the name of the class 
in the STRDBG command matching upper and lower-case characters.  As well, 
you don't enter in the extension of class.  So my class name 
'OraCon.class' was entered in as OraCon.

Another trick I used was to set a breakpoint in my RPG code to break at 
the point where the Java class was instantiated.  Once the program hit 
this breakpoint, I then used F14 from within STRDBG and added the Java 
Class right after it was created.  I was then able to use Option 5 
'Display Module Source' and then set a break point in my Java code and 
then step through my Java class.


...Paul