Gwt-gae-image-gallery is a project mainly written in Java, based on the MIT license.
Image Gallery demo application showing the high performance image serving API at work
This is a demo of using Google Web Toolkit, Google App Engine and GAE's high performance image serving library to build a basic image gallery application. Read more about this API here:
http://code.google.com/appengine/docs/java/javadoc/com/google/appengine/api/images/ImagesService.html#getServingUrl(com.google.appengine.api.blobstore.BlobKey, int, boolean)
Note that to deploy this, you will require your GAE application to be billing-enabled. This app was built using GWT 2.0.4 and GAE SDK 1.3.7.
To test this application, you will need to add the requisite JARs to your build path. See this page for the required classes:
http://code.google.com/appengine/docs/java/tools/localunittesting.html