Comment by ido....@gmail.com: In Improved request batching section the sample has typo: ctxB.requestB().to(new Receiver<Boolean>(){}); should be
ctxB.requestB().to(new Receiver<Integer>(){}); For more information: http://code.google.com/p/google-web-toolkit/wiki/RequestFactory_2_4 -- http://groups.google.com/group/Google-Web-Toolkit-Contributors