gwt – 如何将每个回调包装在一个地方以改善错误处理

在我的GWT应用程序中,使用许多不同的服务对服务器进行了许多不同的异步调用.为了做更好的错误处理,我想包装所有的回调,以便我可以在一个地方处理InvocationExceptions之类的异常.实现AsyncCallback的超类实际上不是一个选项,因为这意味着我必须修改每个异步调用.

RpcServiceProxy#doCreateRequestCallback()看起来像要覆盖的方法.很简单.我只是看不出如何让GWT使用我的新课程.

陈述问题的另一种方式是

How do I make GWT use my own subclass of RpcServiceProxy?

为了包装每个AsynCallback< T>传递给任何需要覆盖RemoteServiceProxy#doCreateRequestCallback()的RemoteService,因为每个AsynCallback< T>在RPC调用发生之前将其传递给此处.

以下是执行此操作的步骤：

正如@ChrisLercher所提到的,您需要定义自己的代理生成器,以便在每次生成RemoteService代理时进入.首先扩展ServiceInterfaceProxyGenerator并重写#createProxyCreator().

/**
 * This Generator extends the default GWT {@link ServiceInterfaceProxyGenerator} and replaces it in the
 * co.company.MyModule GWT module for all types that are assignable to
 * {@link com.google.gwt.user.client.rpc.RemoteService}. Instead of the default GWT {@link ProxyCreator} it provides the
 * {@link MyProxyCreator}.
 */
public class MyServiceInterfaceProxyGenerator extends ServiceInterfaceProxyGenerator {
    @Override
    protected ProxyCreator createProxyCreator(JClassType remoteService) {
        return new MyProxyCreator(remoteService);
    }
}

在MyModule.gwt.xml中,使用延迟绑定来指示GWT在生成RemoteService类型时使用您的代理生成器进行编译：

<generate-with 
   class="com.company.ourapp.rebind.rpc.MyServiceInterfaceProxyGenerator">
    <when-type-assignable class="com.google.gwt.user.client.rpc.RemoteService"/>
</generate-with>

扩展ProxyCreator并覆盖#getProxySupertype().在MyServiceInterfaceProxyGenerator#createProxyCreator()中使用它,以便您可以为所有生成的RemoteServiceProxies定义基类.

/**
 * This proxy creator extends the default GWT {@link ProxyCreator} and replaces {@link RemoteServiceProxy} as base class
 * of proxies with {@link MyRemoteServiceProxy}.
 */
public class MyProxyCreator extends ProxyCreator {
    public MyProxyCreator(JClassType serviceIntf) {
        super(serviceIntf);
    }

    @Override
    protected Class<? extends RemoteServiceProxy> getProxySupertype() {
        return MyRemoteServiceProxy.class;
    }
}

确保MyProxyCreator和MyServiceInterfaceProxyGenerator都位于一个不会被GWT交叉编译为javascript的包中.否则你会看到如下错误：

[ERROR] Line XX: No source code is available for type com.google.gwt.user.rebind.rpc.ProxyCreator; did you forget to inherit a required module?

您现在可以扩展RemoteServiceProxy并覆盖#doCreateRequestCallback()！在这里,您可以执行任何您喜欢的操作,并将其应用于发送到服务器的每个回调.确保将此类以及此处使用的任何其他类(在我的案例中为AsyncCallbackProxy)添加到要进行交叉编译的客户端程序包中.

/**
 * The remote service proxy extends default GWT {@link RemoteServiceProxy} and proxies the {@link AsyncCallback} with
 * the {@link AsyncCallbackProxy}.
 */
public class MyRemoteServiceProxy extends RemoteServiceProxy {
    public MyRemoteServiceProxy(String moduleBaseURL, String remoteServiceRelativePath, String serializationPolicyName,
                                 Serializer serializer) {
        super(moduleBaseURL, remoteServiceRelativePath, serializationPolicyName, serializer);
    }

    @Override
    protected <T> RequestCallback doCreateRequestCallback(RequestCallbackAdapter.ResponseReader responseReader,
                                                          String methodName, RpcStatsContext statsContext,
                                                          AsyncCallback<T> callback) {
        return super.doCreateRequestCallback(responseReader, methodName, statsContext, new AsyncCallbackProxy<T>(callback));
    }
}

参考文献：

> DevGuideCodingBasicsDeferred.html
> An example applied to performance tracking