This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
What is the problem? Ajax within a portlet is very similar to Ajax in a Servlet/JSP application. Only thing is, ifyou're calling a Servlet or JSP resource, it must be packaged within the same war file. Maybe that's your issue?