Eclipse's Web Tools Platform (WTP) is a set of tools that make it easy to develop Java EE applications. App Engine Java applications are Java EE web applications.
When GPE was first released, it did not support generating App Engine projects that were compatible with WTP. Now, we've added support for this! You can also import an App Engine application packaged as a Maven project (see Using Apache Maven ), as described in Importing a Maven Project . The feature is still in preview, but is under active development. You can find out more about it in the App Engine Web Tools Platform pages.