Debugging JSP page in Eclipse depends largely on the plugin that you are using. If its Sysdeo plugin then all you need to do is create a Tomcat project in eclipse and add all your jsp file to complete your web application.
Then when you run the Tomcat for your webapplication it will generate the Java files for your JSP pages as soon as you access them. The location is typically will be a work folder in the project that you have created.
Once you have java source files you can debug them using the eclipse ide.