AribaWeb is a full stack Java Ajax framework for developing applications, mostly on the web. It comes with so many features and tools so the issues you would have to deal with in your day to day web development is already sorted out.
Among its many features it the ability to generate your UI from metadata defined in stylesheet like OSS files and also from annotations defined on your classes.
This is very beautiful because you can generate different UI based on the device or the context in use. One very practical application is for web applications that will have to run on mobile devices - and this is the area I want to explore most once I have full grasp on AribaWeb.