Does your JSP page work? If you add some HTML code to it, do you see it on the screen? Does calling the class from JSP page work? If you add some println statements in your class, do they get printed out (most likely to your web container's log file). If that works, maybe there are some security restrictions on JSP (kind of like on Applets when they're not allowed to do everything what a regular Java application can)?
If it does not work in a JSP, call a servlet that will kill the process for you and then redirect you to a JSP page that dynamically lists down active processes. Do you see any error stacks when you use the code in a jsp ?