First, if I were going to do AJAX, I'd use the
Struts jQuery plugin. It makes AJAX much easier than doing it yourself.
That said, what have you done to debug your application? Have you used a JavaScript debugger like
FireBug to see that your JavaScript is working? What return code are you getting from your HTTP request? Are you checking your server logs to check for errors there? You don't show us success.jsp. Does it exist? Note your index.jsp expects XML. What does success.jsp render?