c# - IErrorHandler 在 HTTP 状态代码为 401 Unauthorized 时返回错误的消息正文

Question

我已经实现了 IErrorHandler 来处理在我的 restful WCF 服务的构造函数中抛出的授权异常。当捕获到一般异常时，我的自定义类型按预期返回，但 ContentType header 不正确。

HTTP/1.1 500 Internal Server Error
Content-Type: application/xml;
...

{"ErrorMessage":"Error!"}

然而，当错误处理程序尝试返回 401 Unauthorized http 状态代码时，消息正文将被覆盖为默认类型，但 ContentType header 是它应该的。

HTTP/1.1 401 Unauthorized
Content-Type: application/json; 
...

{"Message":"Authentication failed.","StackTrace":null,"ExceptionType":"System.InvalidOperationException"}

显然这里有问题，但我不确定是什么。

我如何实现 IErrorHandler 以使其在 json 中返回带有正确 header 的自定义类型？

BaseDataResponseContract 对象:

[Serializable]
[DataContract( Name = "BaseDataResponseContract" )]
public class BaseDataResponseContract
{
    [DataMember]
    public string ErrorMessage { get; set; }

} // end

这是我要返回的对象。我的应用程序中的所有其他对象都继承自该对象。当抛出异常时，我们真正关心的是 http 状态代码和错误消息。

IErrorHandler 实现(为简洁起见未显示日志记录):

namespace WebServices.BehaviorsAndInspectors
{
    public class ErrorHandler : IErrorHandler
    {
        public bool HandleError(Exception error)
        {
            return true;

        } // end

        public void ProvideFault(Exception ex, MessageVersion version, ref Message fault)
        {
            // Create a new instance of the object I would like to return with a default message
            var baseDataResponseContract = new BaseDataResponseContract { ErrorMessage = "Error!" };

            // Get the outgoing response portion of the current context 
            var response = WebOperationContext.Current.OutgoingResponse;

            // Set the http status code 
            response.StatusCode = HttpStatusCode.InternalServerError;

            // If the exception is a specific type change the default settings
            if (ex.GetType() == typeof(UserNotFoundException))
            {
                 baseDataResponseContract.ErrorMessage = "Invalid Username!";
                 response.StatusCode = HttpStatusCode.Unauthorized;
            }    

            // Create the fault message that is returned (note the ref parameter)
            fault = Message.CreateMessage(version, "", baseDataResponseContract, new DataContractJsonSerializer(typeof(BaseDataResponseContract)));

            // Tell WCF to use JSON encoding rather than default XML
            var webBodyFormatMessageProperty = new WebBodyFormatMessageProperty(WebContentFormat.Json);
            fault.Properties.Add(WebBodyFormatMessageProperty.Name, webBodyFormatMessageProperty);

            // Add ContentType header that specifies we are using json 
            var httpResponseMessageProperty = new HttpResponseMessageProperty();
            httpResponseMessageProperty.Headers[HttpResponseHeader.ContentType] = "application/json";
            fault.Properties.Add(HttpResponseMessageProperty.Name, httpResponseMessageProperty);

        } // end

    } // end class

} // end namespace

IServiceBehavior 实现:

namespace WebServices.BehaviorsAndInspectors
{
    public class ErrorHandlerExtensionBehavior : BehaviorExtensionElement, IServiceBehavior
    {
        public override Type BehaviorType
        {
            get { return GetType(); }
        }

        protected override object CreateBehavior()
        {
            return this;
        }

        private IErrorHandler GetInstance()
        {
            return new ErrorHandler();
        }

        void IServiceBehavior.AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) { } // end

        void IServiceBehavior.ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        {
            var errorHandlerInstance = GetInstance();

            foreach (ChannelDispatcher dispatcher in serviceHostBase.ChannelDispatchers)
            {
                dispatcher.ErrorHandlers.Add(errorHandlerInstance);
            }
        }

        void IServiceBehavior.Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { } // end

    } // end class

} // end namespace

网络配置:

<system.serviceModel>

    <services>      
      <service name="WebServices.MyService">
        <endpoint binding="webHttpBinding" contract="WebServices.IMyService" />
      </service>
    </services>

    <extensions>      
      <behaviorExtensions>        
        <!-- This extension if for the WCF Error Handling-->
        <add name="ErrorHandlerBehavior" type="WebServices.BehaviorsAndInspectors.ErrorHandlerExtensionBehavior, WebServices, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />      
      </behaviorExtensions>    
    </extensions>

    <behaviors>          
      <serviceBehaviors>        
        <behavior>
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true"/>
          <ErrorHandlerBehavior />
        </behavior>     
      </serviceBehaviors>    
    </behaviors>

    ....
</system.serviceModel>

最后，我在使用 WebFaultException 时看到了类似的行为。我的想法是，这是一些深藏不露的 .Net 恶作剧的结果。我选择实现 IErrorHandler，这样我就可以捕获任何其他可能无法处理的异常。

引用:

https://msdn.microsoft.com/en-us/library/system.servicemodel.dispatcher.ierrorhandler(v=vs.100).aspx

http://www.brainthud.com/cards/5218/25441/which-four-behavior-interfaces-exist-for-interacting-with-a-service-or-client-description-what-methods-do-they-implement-and

其他例子:

IErrorHandler doesn't seem to be handling my errors in WCF .. any ideas?

How to make custom WCF error handler return JSON response with non-OK http code?

How do you set the Content-Type header for an HttpClient request?

Answer 1

我不太确定您的应用程序是如何实现的。根据你的描述，我建议使用visual studio调试你的ErrorHandler，看看异常是否到达你的回调。

如果是，请以您想要的方式手动构建 soap 故障或响应。

如果不是，则意味着异常发生在到达您的服务操作之前，它可能已经在 Channel 堆栈中失败，在这种情况下，一种简单的方法是添加额外的 HttpModule 来自定义或映射响应。或者您可以尝试在 channel 堆栈中自定义编码器。