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javagoogle-app-enginegwtrequestfactory

ClassCastException in RequestFactory GWT/GAE

I have three Proxy-Interface:

IModuleBaseProxy
IBerichtModuleProxy extends IModuleBaseProxy
INewsModuleProxy extends IModuleBaseProxy

The funciton clientfactory.getModule(id) returns a IModuleBaseProxy

public IModuleBaseProxy getModule(String id) {
    return moduleList.get(id);
}

I have following Problem, while 1. works, 2. doesn't work:

1.

INewsModuleProxy nm = (INewsModuleProxy) clientfactory.getModule(id);

2.

IBerichtModuleProxy bm =(IBerichtModuleProxy) clientfactory.getModule(id);

I get following Exception:

Caused by: java.lang.ClassCastException: ch.zhaw.ams.client.core.module.IModuleBaseProxyAutoBean_com_google_web_bindery_requestfactory_shared_impl_EntityProxyCategory_com_google_web_bindery_requestfactory_shared_impl_ValueProxyCategory_com_google_web_bindery_requestfactory_shared_impl_BaseProxyCategory$1 cannot be cast to ch.zhaw.ams.module.football.sfv.bericht.client.IBerichtModuleProxy

Full Stacktrace:

14:21:50.922 [ERROR] [simpleams] Uncaught exception escaped

com.google.web.bindery.event.shared.UmbrellaException: One or more exceptions caught, see full set in UmbrellaException#getCauses
    at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$StandardPayloadDialect.processPayload(AbstractRequestContext.java:387)
    at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$5.onTransportSuccess(AbstractRequestContext.java:1108)
    at ch.zhaw.ams.client.core.AmsRequestTransport$1.onTransportSuccess(AmsRequestTransport.java:30)
    at com.google.web.bindery.requestfactory.gwt.client.DefaultRequestTransport$1.onResponseReceived(DefaultRequestTransport.java:136)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.GeneratedMethodAccessor77.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
    at sun.reflect.GeneratedMethodAccessor28.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
    at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassCastException: ch.zhaw.ams.client.core.module.IModuleBaseProxyAutoBean_com_google_web_bindery_requestfactory_shared_impl_EntityProxyCategory_com_google_web_bindery_requestfactory_shared_impl_ValueProxyCategory_com_google_web_bindery_requestfactory_shared_impl_BaseProxyCategory$1 cannot be cast to ch.zhaw.ams.module.football.sfv.bericht.client.IBerichtModuleProxy
    at ch.zhaw.ams.module.football.sfv.bericht.client.presenter.ams.BerichtPresenter.<init>(BerichtPresenter.java:74)
    at ch.zhaw.ams.client.ams.IReflectiveAmsFactoryWrapper.newInstance(IReflectiveAmsFactoryWrapper.java:5)
    at ch.zhaw.ams.client.ams.presenter.AmsPresenter$1.onSuccess(AmsPresenter.java:124)
    at ch.zhaw.ams.client.ams.presenter.AmsPresenter$1.onSuccess(AmsPresenter.java:1)
    at com.google.web.bindery.requestfactory.shared.impl.AbstractRequest.onSuccess(AbstractRequest.java:129)
    at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$StandardPayloadDialect.processPayload(AbstractRequestContext.java:354)
    at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$5.onTransportSuccess(AbstractRequestContext.java:1108)
    at ch.zhaw.ams.client.core.AmsRequestTransport$1.onTransportSuccess(AmsRequestTransport.java:30)
    at com.google.web.bindery.requestfactory.gwt.client.DefaultRequestTransport$1.onResponseReceived(DefaultRequestTransport.java:136)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
    at sun.reflect.GeneratedMethodAccessor77.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
    at sun.reflect.GeneratedMethodAccessor28.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
    at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
    at java.lang.Thread.run(Thread.java:662)

Does anybody see the point?

kindest Sam

Solution

  • OK, without seeing your code, I would assume that when you get the exception you have returned a INewsModuleProxy and are trying to treat it as a IBerichtModuleProxy. To prove this to yourself you could print the type of the object before you return it.

    I'm tempted to question your design as your return type suggests that clients should be unconcerned with the specific implementation. If this is true, why are you down-casting?

    R