This is the reference manual to Vaadin. It will give you an introduction and work as your guide for building great looking, high performing web applications.Vaadin is an open source web framework. All of your code is executed on the server’s JVM, while the UI is automatically rendered inside the browser as Web Components and interactions are automatically communicated between the browser and the server. Vaadin is component based so you can build your UI using layouts, components and event listeners.