Gwt 使用RequestFactory和Objectify时出现了一个奇怪的异常

我看了一看谷歌IO的例子，发现它可以正常工作。我试图向项目中添加一些功能，但不断从服务器中获取异常（调用了onFailure方法），并且stacktrace是

19:47:36.070 [ERROR] [crowd] 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:299)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$4.onTransportSuccess(AbstractRequestContext.java:951)
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.NativeMethodAccessorImpl.invoke0(Native Method)
......stacktrace

Caused by: java.lang.RuntimeException: Server Error: No class 'com.trial.gwtgae.server.domain.Sketch2' was registered
at com.google.web.bindery.requestfactory.shared.Receiver.onFailure(Receiver.java:36)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequest.onFail(AbstractRequest.java:113)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$StandardPayloadDialect.processPayload(AbstractRequestContext.java:271)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$4.onTransportSuccess(AbstractRequestContext.java:951)
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.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
...more stacktrace

我创建了名为Sketch2的类Sketch的精确克隆，并在我的RequestFactory接口中创建了SketchDao、SketchProxy和SqetchRequest的克隆

无论如何都会引发异常。（我尝试重新编译、重新启动、清理生成的文件，尝试使用IDEA-同样的问题）

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知道为什么会发生这种情况吗？

您必须注册要与objectify一起使用的类。大概是这样的：

factory.register(com.trial.gwtgae.server.domain.Sketch2.class);

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尝试查看异常引发的行号。当您有一些愚蠢的小错误时，例如尝试将一行添加到太小的网格时，通常会引发此异常。也许你导入了错误的东西？异常中没有我的代码行。每一个克隆都和它的原始草图类在同一个包中。我没有发现任何关于将类注册到工厂的信息。RequestFactory没有名为register的方法。即使是带有草图的原始示例也没有注册任何类。我说的是objectify。您必须注册所有实体类。您还可以使用ObjectifyService注册类