Vaadin includes support to run Vaadin applications in the Google App Engine (GAE). The most essential requirement for GAE is the ability to serialize the application state. Vaadin applications are serializable through the java.io.Serializable interface.

To run as a GAE application, an application must use GAEApplicationServlet instead of ApplicationServlet in web.xml, and of course implement the java.io.Serializable interface for all persistent classes. You also need to enable session support in appengine-web.xml with:

<sessions-enabled>true</sessions-enabled>

The Vaadin Project wizard can create the configuration files needed for GAE deployment. See Section 2.3.1, “Creating the Project”. When the Google App Engine deployment configuration is selected, the wizard will create the project structure following the GAE Servlet convention instead of the regular Servlet convention. The main differences are:

  • Source directory: src/main/java
  • Output directory: war/WEB-INF/classes
  • Content directory: war