GWT

Google Web Toolkit, from Google. Google Web Toolkit (GWT /ˈɡwɪt/), or GWT Web Toolkit,[1] is an open-source set of tools that allows web developers to create and maintain JavaScript front-end applications in Java. It is licensed under the Apache License 2.0. https://en.wikipedia.org/wiki/Google_Web_Toolkit

for building AJAX apps

http://code.google.com/webtoolkit/