I've seen a lot of people asking how to debug JSP's with different application servers. We are in the process of testing the approach I'm about to outline, but we don't have it working as yet. Our application server is Weblogic, but the approach should be similar for other app servers.
Our approach is to precompile the JSP files into class files, adding the java files generated by the precompile to our project and using these generated files when setting JSP breakpoints. Our thinking is after the compilation process, JSP files are just java classes and the remote debugging features of IDEA can be used to debug these files. If we get it working, I'll post details on exactly what we had to do with Weblogic that others can use as a guide for their particular application server.
I know it's thin on details right now, but I thought I'd post it because of all the requests asking for help with JSP debugging.