[SOLVED] RequestFactory Nullpointer Exception with EntityProxy

I want to send Generic Objects through the wire with RequestFactories. Because I want to test on the server what Class it is and return a value from Database for the requested class.

For example i send the request with a NewsProxy or a ProfileProxy (each extends EntityProxy) or some other proxy.

This is my client code:

private void loadComments() {
    NewsProxy proxy = **Some News Proxy**
    ICommentRequest commentRequest = clientfactory.getRequestFactory().commentRequest();
    commentRequest.getComments(proxy).fire();

}

Interface ICommentRequest:

@Service(value = Comment.class, locator = OperatorServiceLocator.class)
public interface ICommentRequest extends RequestContext {
    Request<List<ICommentProxy>> getComments(EntityProxy object); 
}

Server impl: Comment.java:

public static List<Comment> getComments(Object o) {

    ...

}

When I fire this event, I get an NullPointerException. I don't know where...

Dec 30, 2012 12:39:25 PM com.google.web.bindery.requestfactory.server.RequestFactoryServlet doPost
SEVERE: Unexpected error
java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    at com.google.web.bindery.requestfactory.server.ServiceLayerCache.getOrCache(ServiceLayerCache.java:225)
    at com.google.web.bindery.requestfactory.server.ServiceLayerCache.resolveClass(ServiceLayerCache.java:156)
    at com.google.web.bindery.requestfactory.server.RequestState$1.getTypeFromToken(RequestState.java:76)
    at com.google.web.bindery.requestfactory.shared.impl.IdFactory.getId(IdFactory.java:198)
    at com.google.web.bindery.requestfactory.server.RequestState.getBeansForPayload(RequestState.java:142)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.processOperationMessages(SimpleRequestProcessor.java:509)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:218)
    at com.google.web.bindery.requestfactory.server.SimpleRequestProcessor.process(SimpleRequestProcessor.java:135)
    at com.google.web.bindery.requestfactory.server.RequestFactoryServlet.doPost(RequestFactoryServlet.java:133)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at ch.zhaw.ams.server.auth.AuthFilter.doFilter(AuthFilter.java:35)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:61)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:383)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)