Didn't have time to deeply look at this. Only obvious thing I noted is that the diff lib should be test scope.
http://codereview.appspot.com/157161/diff/3092/2084 File java/gadgets/pom.xml (right): http://codereview.appspot.com/157161/diff/3092/2084#newcode133 java/gadgets/pom.xml:133: <artifactId>diff_match_patch</artifactId> This should be <scope>test</scope> so we don't include this in the deployed artifacts. http://codereview.appspot.com/157161
