Of all times debugging jsp code is the most challenging of all times to me that anything else.

And for that, I came across the linked jsp and the following code snippet in the footer jsp of the application:

      <%@include file="/WEB-INF/jsp/debug_session.jsp"%>

keep the debug_session.jsp as per the path defined in the above snippet.
To check all request & response variable while developing, just update the current url as:

  
http://localhost:8080/context-path/login.jsp?debug=jsp

And you can easily check all variable without trying to search them in the request object on your IDE, while debugging!

Here is the debug_session.jsp

~rohit.