Ajaxifying existing J2EE projects

Introduction :
This document gives the steps for extending an existing J2EE application using the Spring MVC/ Spring Portlet MVC (JSR 168 compliant) / Hibernate or any other ORM stack.

There are basically 2 types of JavaScript libraries.
1.Client Side Libraries : e.g. Sciptaculous / Dojo / YUI Library, provide ready to use Widgets or client side javascript affects.
2.Server Side JavaScript libraries : Which compile javascript code on the server side. Normally these types of libraries handle ajax call from the client side and connect to the code on the server and fetch back the result in javascript. E.g DWR, JSON.

DWR is a natural choice for Java Web Projects, Simply because it was created with the mindset of having Java on the Server Side.