Butterfly Web UI is a component based Java Web application framework. Like the rest of the Butterfly Components, Butterfly Web UI is extremely small and very flexible. Butterfly Web UI uses Butterfly Container internally, a state of the art dependency injection container. Using Butterfly Web UI, it is easy both to generate HTML for a Web browser or XML or JSON for a RIA frontend (Flex, JavaFX, Silverlight) or AJAX frontend. You also can easily create HTML layout templates that are reused throughout your Web application, so you don't have the layout hardcoded into every page. You can easily mix RIA and non-RIA Web application technology in the same Web application.