Debug j2ee application

Hi,
I'm having on2 j2ee application running on my test server. Is there anyway to debug the application.
The problem is i'm supposed to maintain the application and no documentation about system flow or database mapping is available. It is typical MVC architecture and uses EJB. Can anyone tell me the best suitable way to debug the same.
TIA
Grishma

In order to tackle the "no documentation" problem, I'd suggest to simply read the code and scribble notes about dependencies and execution sequences on paper.
In order to debug the code running on an application server, you need to
1) Start the server in a mode which has debugging enabled
2) Set breakpoints in your IDE
3) Point your IDE (with debugging features) to the correct <address>:<port>

well, i'm using oracle 9i AS rel 2 and i'm very much new to it. I'm not using any IDE, however i can use JBuilder if required.
Can you tell me, how to go abt it?? Means any debugging method in oracle 9i???

You should ask this in the Oracle forum but I'll give you something to try out first:
1) Modify your startup script to include the following properties:
-Xdebug
-Xnoagent
-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
2) Start the server (and deploy your application, if it isn't deployed already)
3) Point your IDE's debugger to the server's JVM by doing something like "Debug -> Enable Remote Debugging -> Attach..." and filling in the server's hostname and port (8000 in the example). Anyway, there must be a help page about debugging in JBuilder...

By the way, I found this JBuilder debugging tutorial by Googling.