Vaadin is a Java framework for building modern web applications that look great, perform well and make you and your users happy.
Developers using Eclipse and NetBeans as IDE can easily integrate Vaadin within their projects thanks to the Eclipse and NetBeans plugins. Vaadin is released under Apache License Version 2.0 and is free even for commercial use. However commercial products and services are available by ITMill, the company behind Vaadin framework
Vaadin is a big collection of UI components. There are server-side components like Button, Table, and Tree that you use to compose the application user interface. The components use events, listeners, and data binding to communicate with each other and the business logic. Vaadin is a robust architecture for rapid application development. The component-based architecture together with the data binding features help you to build applications that are easily modularized and refactored as needed.
More information and download at http://vaadin.com