Phobos is a lightweight, scripting-friendly, web application environment running on the Java platform.
It comes with a set of plugins for the NetBeans IDE that cover the complete development process. These include a fully-featured debugger; wizards to help you get started faster; a palette of Ajax widgets that can be dropped on a page, thanks to jMaki; and the ability to generate a standard web application for deployment on any servlet container or Java EE application server.
Update:Work is ongoing on the next release, which will have a version number of 0.6.x. Find out more details here.