Fuse ESB uses karaf server with OSGi.
for the code if anybody has steps to get the debugger for the application it will help.
I am currently using Eclipse In
Java allows you to remote debug any JVM running.
So if you start the ESB with a debug argument, then it will run in debug mode listening on port 5005.
davsclaus:/opt/fuse-esb-7.0.1.fuse-084$ bin/fuseesb debug
Listening for transport dt_socket at address: 5005
Then you can do remote debugging from Eclipse using that port number. This is standard Java remote debugging, and Eclipse has a wizard for that already. Its the debug wizard which has a remote debug functionality.