GWT向客户端抛出异常

Question

有人可以显示在GWT中向客户端抛出异常.

在我的serviceasync接口中我也在我的服务界面中这样做

void ActivateUserAccount(String ActivationCode,AsyncCallback <Boolean> Callback) throws AlreadyActivatedError;

在我的serverimpl;

我这样做是为了抛出异常

public Boolean ActivateUserAccount(String ActivationCode) throws AlreadyActivatedError
    {
....
throw new AlreadyActivatedError();
}

我的例外是以下形式:

public class AlreadyActivatedError extends Exception implements IsSerializable
{
    public AlreadyActivatedError()
    {
        super();
    }
}

Answer 1

不知道为什么hilal的答案被接受,因为它完全是假的.

为了使例外到达客户端的浏览器,你必须抛出一个checked异常是Serializable在服务接口定义.

如果您的服务实现抛出RuntimeException,Web客户端将收到如下通用500错误消息:

   [WARN] Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract my.module.shared.Result my.module.client.service.Service.doSomething() throws my.module.shared.exception.MyCheckedException' threw an unexpected exception: my.module.shared.exception.AuthzRuntimeException: some authz message
    at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    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:487)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:324)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)
Caused by: my.module.shared.exception.AuthzRuntimeException: some authz message
    at my.module.shared.Authz.doSomeCheck(Authz.java:101)
    at my.module.server.ServiceImpl.doSomething(ServiceImpl.java:283)
    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.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:561)
    ... 22 more
[ERROR] 500 - POST /module/userService (127.0.0.1) 57 bytes
   Request headers
      Host: 127.0.0.1:8888
      User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:24.0) Gecko/20100101 Firefox/24.0
      Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
      Accept-Language: en-US,en;q=0.5
      Accept-Encoding: gzip, deflate
      Referer: http://127.0.0.1:8888/foo.html?gwt.codesvr=127.0.0.1:9997
      Cookie: worknet=7k8g41ulbl674dp865t180tji5
      Connection: keep-alive
      Cache-Control: no-cache
      X-GWT-Permutation: HostedMode
      X-GWT-Module-Base: http://127.0.0.1:8888/module/
      Content-Type: text/x-gwt-rpc; charset=utf-8
      Content-Length: 1076
      Pragma: no-cache
   Response headers
      Content-Type: text/plain
(RequestCallbackAdapter.java:209) 2013-10-18 13:16:56,966 [WARN ] Fail ""
com.google.gwt.user.client.rpc.StatusCodeException: 500 The call failed on the server; see server log for details
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:209)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:258)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:412)
    at sun.reflect.GeneratedMethodAccessor40.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)
    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:338)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
    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:242)
    at sun.reflect.GeneratedMethodAccessor37.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)
    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:293)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
    at java.lang.Thread.run(Unknown Source)

Answer 2

只是为了使一切变得清楚：您可以将已检查的Exception（扩展的RuntimeException）异常和未检查的（扩展）异常从服务器抛出到客户端，只要该异常是可序列化的即可。但是，建议抛出已检查的异常，因为它们

表示程序无法直接控制的区域中的无效条件（无效的用户输入，数据库问题，网络中断，文件缺失）。

相反，未经检查的异常

表示程序中的缺陷（错误）-通常将无效的参数传递给非私有方法。

资源

如文档所述，必须满足以下条件才能将异常发送到客户端：

• 它必须扩展Exception（注意这样RuntimeException做）。
• 它必须是可序列化的。简而言之：Implement Serializable，具有一个无参数的构造函数，并且所有字段都可序列化。
• 在您的*Service接口中，您需要throws向该方法添加一个可以引发异常的声明。请注意，您不需要将throws声明添加到*Async接口。

设置好之后，您就可以在中的onFailure方法中处理异常AsyncCallback。

基于GWT网站上的指南中的示例，一些代码将所有部分放在一起显示：

DelistedException.java

public class DelistedException extends Exception implements Serializable {

  private String symbol;

  // Note the no-args constructor
  // It can be protected so that only subclasses could use it
  // (because if they want to be serializable too, they'll need
  // a no-args constructor that calls the superclasses' no-args constructor...)
  protected DelistedException() {
  }

  public DelistedException(String symbol) {
    this.symbol = symbol;
  }

  public String getSymbol() {
    return this.symbol;
  }
}

StockPriceService.java

@RemoteServiceRelativePath("stockPrices")
public interface StockPriceService extends RemoteService {
  StockPrice[] getPrices(String[] symbols) throws DelistedException;
}

StockPriceServiceAsync.java

public interface StockPriceServiceAsync {
  void getPrices(String[] symbols, AsyncCallback<StockPrice[]> callback);
}

在客户端

AsyncCallback<StockPrice[]> callback = new AsyncCallback<StockPrice[]>() {
  public void onFailure(Throwable caught) {
    if (caught instanceof DelistedException) {
      // Do something with it
    } else {
      // Probably some unchecked exception,
      // show some generic error message
  }

  public void onSuccess(StockPrice[] result) {
    // Success!
  }
};

stockPriceService.getPrices(symbols, callback);