Its a very basic question. I have a moderate size j2ee web application with components as JSPs,servlets and java logic.I have no documentation for that and no help.Kindly let me know is there any systematic way to study the code.My intention is to understand the program flow from jsp to servlet, between classes and methods and to understand the functionalities of the methods.
1. Find a breakpoint close to where something tangible happens. For example, if you change a field in the UI, and can find where that value is saved, that's useful IMHO. Because you have a place of "cause and effect", which is a useful "foothold".
2. With the above breakpoint, you can do 2 things: (a) look at the stacktrace, and get a feel for the calling hierarchy (b) look at the local variables and their members. From this, you can start to branch out. I would pay close attention to abstract base classes because they may be key parts of the architecture.
Another idea is to use the Javadoc and/or a tool like Doxygen to try and see what is going on from static analysis. Here, you want to start to see relationships among the classes. IMHO, this is not as useful as debugging though.