Question

我刚开始使用WCF并且正在尝试验证支持JSON和XML的WCF休息服务中的错误处理。 My test service生成错误，但无论我尝试什么，我都无法获取my client来获取错误的详细信息（并且行为因请求格式和http状态代码而异）：

我的测试服务生成错误如下：

public Data GetResponse()
{
    throw new WebFaultException<ErrorDetails>(
        new ErrorDetails {ErrorMessage = "Server Config Value not set"},
        HttpStatusCode.OK
        );
}

这很合理地通过电汇发送：

{"ErrorMessage":"Server Config Value not set"}

和

<ErrorDetails xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <ErrorMessage>Server Config Value not set</ErrorMessage>
</ErrorDetails>

我的客户端定义为FaultContract：

[OperationContract]
[WebInvoke(
    UriTemplate="/response",
    Method="GET",
    RequestFormat = WebMessageFormat.Xml, // or .Json
    ResponseFormat = WebMessageFormat.Xml // or .Json
    )]
[FaultContract(typeof(ErrorDetails), Namespace="")]
Data GetResponse();

以下是（格式/状态代码）的完整错误消息：

XML /冲突：

请求回复 CommunicationException：远程服务器返回意外响应：（409）Conflict。，System.Collections.ListDictionary 内部，System.ServiceModel.ProtocolException 按一个键退出...

和XML / OK：

请求回复例外：无法使用根名称'ErrorDetails'和根命名空间''反序列化XML主体（对于操作'GetResponse'而言 d使用DataContractSerializer的合约（'IClient'，''））。确保将与XML对应的类型添加到know中 n类型服务的集合。，System.Collections.ListDictionaryInternal 按一个键退出...

和JSON /冲突：

请求回复 CommunicationException：远程服务器返回意外响应：（409）Conflict。，System.Collections.ListDictionary 内部，System.ServiceModel.ProtocolException 按一个键退出...

和JSON / OK：

请求回复响应：请求完成按一个键退出...

客户端代码以正确的顺序捕获异常：

try
{
    Console.WriteLine("Requesting response");
    Console.WriteLine("Response: " + client.GetResponse().Message);
    Console.WriteLine("Request complete");
}
// sanity check, just in case...
catch (WebFaultException<ErrorDetails> ex)
{
    Console.WriteLine("WebFaultException<ErrorDetails>: " + ex.Detail.ErrorMessage + ", " + ex.Reason);
}
catch (FaultException<ErrorDetails> ex)
{
    Console.WriteLine("FaultException<ErrorDetails>: " + ex.Detail.ErrorMessage + ", " + ex.Reason);
}
catch (FaultException ex)
{
    Console.WriteLine("FaultException: " + ex.Message + ", " + ex.Reason);
}
catch (CommunicationException ex)
{
    Console.WriteLine("CommunicationException: " + ex.Message + ", " + ex.Data + ", " + ex.GetType().FullName);
}
catch (Exception ex)
{
    Console.WriteLine("Exception: " + ex.Message + ", " + ex.Data);
}

我必须做什么才能抛出FaultException<ErrorDetails>，我可以访问ErrorDetails？

注意：gist应该是完全可编译的并且可以运行。

Answer 1

无法在WCF REST客户端（从WCF 4.0版开始）服务中使用Faults / FaultContract作为错误处理机制：

WCF列表中的每one thread：

在WCF Rest服务中没有SOAP消息，因此您无法将FaultException返回给客户端。实际上，相应的状态代码作为HTTP标头返回给请求者，允许请求者确定调用的结果。

来自StackOverflow post：

错误是SOAP协议的一部分，在REST方案中不可用

考虑选项

FaultContract - FaultContractAttribute适用于SOAP信封，但不适用于WCF REST服务。如果您将格式化为SOAP信封的XML发送到可以使其工作，但是您没有使用合理的自定义错误消息。

IErrorHandler - 快速阅读文档表明这是针对该服务的，并认为这是一个新手错误：“允许实施者控制返回给调用者的错误消息，并可选择执行自定义错误处理，如日志“。

Message Inspectors - AfterReceiveRequest未执行，因为首先抛出CommunicationException。

解决方法

经过大量挖掘后，我found one blogger建议创建一个帮助程序类，以从嵌入在异常对象中的响应流中提取信息。这是他的实现，原样是：

public static void HandleRestServiceError(Exception exception, Action<TServiceResult> serviceResultHandler, Action<TServiceFault> serviceFaultHandler = null, Action<Exception> exceptionHandler = null) { var serviceResultOrServiceFaultHandled = false; if (exception == null) throw new ArgumentNullException("exception"); if (serviceResultHandler == null) throw new ArgumentNullException("serviceResultHandler"); // REST uses the HTTP procol status codes to communicate errors that happens on the service side. // This means if we have a teller service and you need to supply username and password to login // and you do not supply the password, a possible scenario is that you get a 400 - Bad request. // However it is still possible that the expected type is returned so it would have been possible // to process the response - instead it will manifest as a ProtocolException on the client side. var protocolException = exception as ProtocolException; if (protocolException != null) { var webException = protocolException.InnerException as WebException; if (webException != null) { var responseStream = webException.Response.GetResponseStream(); if (responseStream != null) { try { // Debugging code to be able to see the reponse in clear text //SeeResponseAsClearText(responseStream); // Try to deserialize the returned XML to the expected result type (TServiceResult) var response = (TServiceResult) GetSerializer(typeof(TServiceResult)).ReadObject(responseStream); serviceResultHandler(response); serviceResultOrServiceFaultHandled = true; } catch (SerializationException serializationException) { // This happens if we try to deserialize the responseStream to type TServiceResult // when an error occured on the service side. An service side error serialized object // is not deserializable into a TServiceResult // Reset responseStream to beginning and deserialize to a TServiceError instead responseStream.Seek(0, SeekOrigin.Begin); var serviceFault = (TServiceFault) GetSerializer(typeof(TServiceFault)).ReadObject(responseStream); if (serviceFaultHandler != null && serviceFault != null) { serviceFaultHandler(serviceFault); serviceResultOrServiceFaultHandled = true; } else if (serviceFaultHandler == null && serviceFault != null) { throw new WcfServiceException<TServiceFault>() { ServiceFault = serviceFault }; } } } } } // If we have not handled the serviceResult or the serviceFault then we have to pass it on to the exceptionHandler delegate if (!serviceResultOrServiceFaultHandled && exceptionHandler != null) { exceptionHandler(exception); } else if (!serviceResultOrServiceFaultHandled && exceptionHandler == null) { // Unable to handle and no exceptionHandler passed in throw exception to be handled at a higher level throw exception; } }

Answer 2

我用过这个：

 try
            {
              //wcf service call
            }
            catch (FaultException ex)
            {
               throw new Exception( (ex as WebFaultException<MyContractApplicationFault>).Detail.MyContractErrorMessage );                
            }

WCF：FaultContract设置但不导致在REST服务中捕获FaultException <t> </t>

2 个答案: