Vaadin 7 UI Design By Example Beginner's Guide

Extensions

In Chapter 6, Adding More Components we used the FileDownloader extension to add downloading capabilities to a button:

// create an extension
FileDownloader downloader = new FileDownloader(resource);

// extend a component
downloader.extend(button);

Extensions allow us to add functionality at runtime. We can add multiple extensions to the same component, that's something we cannot do by extending a class (in the object oriented sense, of course).