In simplest form we can write logger statements or System.out.println() statements to write messages to log files. When we call a JSP, the log messages get written to logs. With useful information getting logged we can easily debug the code.
Another option in debugging is to link JSP container with an IDE. Once we link IDE debugger to JSP Engine, we can use standard operations of debugging like breakpoint, step through etc.Read the full book at www.amazon.com