I was able to integrate a Vaadin module into our Spring based application. After integration I wanted to run a demo of gantt-charts which is an add-on for Vaadin and found it on
Try to run mvn clean install to compile the widgetset. If you don't want to use command line, right click in your proyect, Run As > Maven install.
You can also compile your widgetset in eclipse. Open your widgetset file and click in the "gear" symbol in the eclipse menu.