我已经实现了IErrorHandler来处理在我的 Restful WCF服务的构造函数中引发的授权异常。当捕获到一般异常时，将按预期返回我的自定义类型，但是ContentType header 不正确。
HTTP/1.1 500 Internal Server Error
Content-Type: application/xml;
...
{"ErrorMessage":"Error!"}
但是，当错误处理程序尝试返回401未经授权的http状态代码时，消息主体将覆盖为默认类型，但ContentType header 应为应有的状态。
HTTP/1.1 401 Unauthorized
Content-Type: application/json;
...
{"Message":"Authentication failed.","StackTrace":null,"ExceptionType":"System.InvalidOperationException"}
显然这里有些问题，但是我不确定是什么。
如何实现IErrorHandler，以使其在json中使用正确的 header 返回我的自定义类型？
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。当引发异常时，我们真正关心的就是http状态代码和错误消息。
IErrorHandler实现(为简便起见，未显示日志):
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
Web.Config:
<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，在使用WebFaultException时，我看到了类似的行为。我的想法是，这是一些深埋的.Net恶作剧的结果。我选择实现IErrorHandler，以便可以捕获可能无法处理的任何其他异常。
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?
最佳答案
我不太确定您的应用程序是如何实现的。根据您的描述，我建议使用Visual Studio调试您的ErrorHandler以查看异常是否到达您的回调。
如果是，请以您想要的方式手动构造您的肥皂故障或响应。
如果不是，则意味着异常在到达您的服务操作之前发生，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。