Can anyone recommend a good tool for performance profiling Java web applications? (Hibernate, Spring, on Tomcat. you know the kind of thing.)

I've been playing with JiP, but I can't seem to get anything useful out of it. The remote control seems to do nothing at all, so I have to start up the server with it on, which takes a while - then I seem to get no output most of the time. Small runs - no problem. Big runs - which is where I get my performance issues - nothing. Irritating to get no output after waiting several hours for a big test run to complete!

Update: Or, perhaps the fact that Tomcat is still running an hour after I've asked it to shut down indicates that JiP is trying to do something? Who knows?