Vaadin is an open source Java UI library for creating rich web user interfaces. Using its component-based API developers can create stunning web applications in plain Java.
With Vaadin you don't have to think about client-server communication (XHR, WebSockets) or writing JavaScript, CSS or markup languages. Instead, you can write UIs in idiomatic Java, like this:
List<Person> personList = backendService.getAllPersons();
Grid<Person> grid = new Grid<>(Person.class);
grid.setItems(personList));
grid.setColumns("firstName", "lastName", "email");
Vaadin only requires a servlet container, and there are integration libraries for Spring and Java EE (CDI). In addition to dozens of built-in components, the Vaadin Directory provides over 500 community made widgets and components for building your application.
The Vaadin Plugin for Eclipse comes with project templates and samples to speed up your development.
Vaadin is Open source (Apache 2.0) but Vaadin Ltd offers professional tools and services for the framework.