Liferay: Using JSONObject for Ajax in Plugin Portlet

Here is a good article about the same

Many times we face situations when we need to use Ajax call from JSP pages. Using jQuery, its very easy to call any JSP through AJAX. You can just call the JSP and show its response from callback into some DOM element.

http://javalibs.blogspot.com/2010/06/liefray-using-jsonobject-for-ajax-in.html