如何使用非OK http代码使自定义WCF错误处理程序返回JSON响应？

Question

我正在使用WCF和WebHttpBinding实现RESTful Web服务.目前我正在处理错误处理逻辑,实现自定义错误处理程序(IErrorHandler); 目的是让它捕获操作抛出的任何未捕获的异常,然后返回一个JSON错误对象(包括说错误代码和错误消息 - 例如{"errorCode":123,"errorMessage":"bla"})回到浏览器用户以及一个HTTP代码,例如BadRequest,InteralServerError或其他任何东西(除了'确定'以外的任何东西).这是我在错误处理程序的ProvideFault方法中使用的代码:

fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage)));
var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json);
fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf);
var rmp = new HttpResponseMessageProperty();
rmp.StatusCode = System.Net.HttpStatusCode.InternalServerError;
rmp.Headers.Add(HttpRequestHeader.ContentType, "application/json");
fault.Properties.Add(HttpResponseMessageProperty.Name, rmp);

- >返回Content-Type:application/json,但状态代码为'OK'而不是'InternalServerError'.

fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage)));
var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json);
fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf);
var rmp = new HttpResponseMessageProperty();
rmp.StatusCode = System.Net.HttpStatusCode.InternalServerError;
//rmp.Headers.Add(HttpRequestHeader.ContentType, "application/json");
fault.Properties.Add(HttpResponseMessageProperty.Name, rmp);

- >返回正确的状态代码,但内容类型现在是XML.

fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage)));
var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json);
fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf);

var response = WebOperationContext.Current.OutgoingResponse;
response.ContentType = "application/json";
response.StatusCode = HttpStatusCode.InternalServerError;

- >返回正确的状态代码和正确的内容类型!问题是http主体现在有文本'无法加载源:http:// localhost:7000/bla ..'而不是实际的JSON数据..

有任何想法吗？我正在考虑使用最后一种方法,只是将JSON放在HTTP StatusMessage头字段而不是在正文中,但这看起来不是很好吗？

Answer 1

实际上,这对我有用.

这是我的ErrorMessage类:

    [DataContract]
    public class ErrorMessage
    {
        public ErrorMessage(Exception error)
        {
            Message = error.Message;
            StackTrace = error.StackTrace;
            Exception = error.GetType().Name;
        }

        [DataMember(Name="stacktrace")]
        public string StackTrace { get; set; }
        [DataMember(Name = "message")]
        public string Message { get; set; }
        [DataMember(Name = "exception-name")]
        public string Exception { get; set; }
    }

结合上面的最后一个片段:

        fault = Message.CreateMessage(version, "", new ErrorMessage(error), new DataContractJsonSerializer(typeof(ErrorMessage)));
        var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json);
        fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf);

        var response = WebOperationContext.Current.OutgoingResponse;
        response.ContentType = "application/json";
        response.StatusCode = HttpStatusCode.InternalServerError; 

这给了我正确的错误,如json.谢谢.:)

Answer 2

以下是基于上述信息的完整解决方案:

是的,你有.您可以创建自定义错误处理程序并执行您的操作.

请参阅附带的代码.

这是自定义错误处理程序:

public class JsonErrorHandler : IErrorHandler
{

    public bool HandleError(Exception error)
    {
        // Yes, we handled this exception...
        return true;
    }

    public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
    {
        // Create message
        var jsonError = new JsonErrorDetails { Message = error.Message, ExceptionType = error.GetType().FullName };
        fault = Message.CreateMessage(version, "", jsonError,
                                      new DataContractJsonSerializer(typeof(JsonErrorDetails)));

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

        // Modify response
        var rmp = new HttpResponseMessageProperty
                      {
                          StatusCode = HttpStatusCode.BadRequest,
                          StatusDescription = "Bad Request",
                      };
        rmp.Headers[HttpResponseHeader.ContentType] = "application/json";
        fault.Properties.Add(HttpResponseMessageProperty.Name, rmp);
    }
}

这是注入错误处理程序的扩展服务行为:

/// <summary>
/// This class is a custom implementation of the WebHttpBehavior. 
/// The main of this class is to handle exception and to serialize those as requests that will be understood by the web application.
/// </summary>
public class ExtendedWebHttpBehavior : WebHttpBehavior
{
    protected override void AddServerErrorHandlers(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        // clear default erro handlers.
        endpointDispatcher.ChannelDispatcher.ErrorHandlers.Clear();

        // add our own error handler.
        endpointDispatcher.ChannelDispatcher.ErrorHandlers.Add(new JsonErrorHandler());
        //BehaviorExtensionElement
    }
}

这是一个自定义绑定,因此您可以在web.config中配置它

/// <summary>
/// Enables the ExtendedWebHttpBehavior for an endpoint through configuration.
/// Note: Since the ExtendedWebHttpBehavior is derived of the WebHttpBehavior we wanted to have the exact same configuration.  
/// However during the coding we've relized that the WebHttpElement is sealed so we've grabbed its code using reflector and
/// modified it to our needs.
/// </summary>
public sealed class ExtendedWebHttpElement : BehaviorExtensionElement
{
    private ConfigurationPropertyCollection properties;
    /// <summary>Gets or sets a value that indicates whether help is enabled.</summary>
    /// <returns>true if help is enabled; otherwise, false. </returns>
    [ConfigurationProperty("helpEnabled")]
    public bool HelpEnabled
    {
        get
        {
            return (bool)base["helpEnabled"];
        }
        set
        {
            base["helpEnabled"] = value;
        }
    }
    /// <summary>Gets and sets the default message body style.</summary>
    /// <returns>One of the values defined in the <see cref="T:System.ServiceModel.Web.WebMessageBodyStyle" /> enumeration.</returns>
    [ConfigurationProperty("defaultBodyStyle")]
    public WebMessageBodyStyle DefaultBodyStyle
    {
        get
        {
            return (WebMessageBodyStyle)base["defaultBodyStyle"];
        }
        set
        {
            base["defaultBodyStyle"] = value;
        }
    }
    /// <summary>Gets and sets the default outgoing response format.</summary>
    /// <returns>One of the values defined in the <see cref="T:System.ServiceModel.Web.WebMessageFormat" /> enumeration.</returns>
    [ConfigurationProperty("defaultOutgoingResponseFormat")]
    public WebMessageFormat DefaultOutgoingResponseFormat
    {
        get
        {
            return (WebMessageFormat)base["defaultOutgoingResponseFormat"];
        }
        set
        {
            base["defaultOutgoingResponseFormat"] = value;
        }
    }
    /// <summary>Gets or sets a value that indicates whether the message format can be automatically selected.</summary>
    /// <returns>true if the message format can be automatically selected; otherwise, false. </returns>
    [ConfigurationProperty("automaticFormatSelectionEnabled")]
    public bool AutomaticFormatSelectionEnabled
    {
        get
        {
            return (bool)base["automaticFormatSelectionEnabled"];
        }
        set
        {
            base["automaticFormatSelectionEnabled"] = value;
        }
    }
    /// <summary>Gets or sets the flag that specifies whether a FaultException is generated when an internal server error (HTTP status code: 500) occurs.</summary>
    /// <returns>Returns true if the flag is enabled; otherwise returns false.</returns>
    [ConfigurationProperty("faultExceptionEnabled")]
    public bool FaultExceptionEnabled
    {
        get
        {
            return (bool)base["faultExceptionEnabled"];
        }
        set
        {
            base["faultExceptionEnabled"] = value;
        }
    }
    protected override ConfigurationPropertyCollection Properties
    {
        get
        {
            if (this.properties == null)
            {
                this.properties = new ConfigurationPropertyCollection
                {
                    new ConfigurationProperty("helpEnabled", typeof(bool), false, null, null, ConfigurationPropertyOptions.None), 
                    new ConfigurationProperty("defaultBodyStyle", typeof(WebMessageBodyStyle), WebMessageBodyStyle.Bare, null, null, ConfigurationPropertyOptions.None), 
                    new ConfigurationProperty("defaultOutgoingResponseFormat", typeof(WebMessageFormat), WebMessageFormat.Xml, null, null, ConfigurationPropertyOptions.None), 
                    new ConfigurationProperty("automaticFormatSelectionEnabled", typeof(bool), false, null, null, ConfigurationPropertyOptions.None), 
                    new ConfigurationProperty("faultExceptionEnabled", typeof(bool), false, null, null, ConfigurationPropertyOptions.None)
                };
            }
            return this.properties;
        }
    }
    /// <summary>Gets the type of the behavior enabled by this configuration element.</summary>
    /// <returns>The <see cref="T:System.Type" /> for the behavior enabled with the configuration element: <see cref="T:System.ServiceModel.Description.WebHttpBehavior" />.</returns>
    public override Type BehaviorType
    {
        get
        {
            return typeof(ExtendedWebHttpBehavior);
        }
    }
    protected override object CreateBehavior()
    {
        return new ExtendedWebHttpBehavior
        {
            HelpEnabled = this.HelpEnabled,
            DefaultBodyStyle = this.DefaultBodyStyle,
            DefaultOutgoingResponseFormat = this.DefaultOutgoingResponseFormat,
            AutomaticFormatSelectionEnabled = this.AutomaticFormatSelectionEnabled,
            FaultExceptionEnabled = this.FaultExceptionEnabled
        };
    }
}

那是web.config

  <system.serviceModel>
<diagnostics>
  <messageLogging logMalformedMessages="true" logMessagesAtTransportLevel="true" />
</diagnostics>
<bindings>
  <webHttpBinding>
    <binding name="regularService" />
  </webHttpBinding>
</bindings>
<behaviors>
  <endpointBehaviors>
    <behavior name="AjaxBehavior">
      <extendedWebHttp />
    </behavior>
  </endpointBehaviors>
  <serviceBehaviors>
    <behavior>
      <!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->
      <serviceMetadata httpGetEnabled="true" httpsGetEnabled="true"/>
      <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
      <serviceDebug includeExceptionDetailInFaults="true"/>
    </behavior>
  </serviceBehaviors>
</behaviors>
<extensions>
  <behaviorExtensions>
    <add name="extendedWebHttp" type="MyNamespace.ExtendedWebHttpElement, MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/>
  </behaviorExtensions>
</extensions>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />
<services>
  <service name="MyWebService">
    <endpoint address="" behaviorConfiguration="AjaxBehavior"
      binding="webHttpBinding" bindingConfiguration="regularService"
      contract="IMyWebService" />
  </service>
</services>

注意:行为扩展应该完全按原样排在一行(WCF中有一个错误).

这是我的客户端(我们的自定义代理的一部分)

 public void Invoke<T>(string action, object prms, JsAction<T> successCallback, JsAction<WebServiceException> errorCallback = null, JsBoolean webGet = null)
    {
        Execute(new WebServiceRequest { Action = action, Parameters = prms, UseGetMethod = webGet },
            t =>
            {
                successCallback(t.As<T>());
            },
            (req, message, err)=>
            {
                if (req.status == 400) //Bad request - that's what we've specified in the WCF error handler.
                {
                    var details = JSON.parse(req.responseText).As<JsonErrorDetails>();
                    var ex = new WebServiceException()
                    {
                        Message = details.Message,
                        StackTrace = details.StackTrace,
                        Type = details.ExceptionType
                    };

                    errorCallback(ex);
                }
            });
    }

Answer 3

在最新版本的WCF(截至2011年11月)中,使用WebFaultException有更好的方法.您可以在服务catch块中按如下方式使用它:

throw new WebFaultException<ServiceErrorDetail>(new ServiceErrorDetail(ex), HttpStatusCode.SeeOther);


[DataContract]
    public class ServiceErrorDetail
    {
        public ServiceErrorDetail(Exception ex)
        {
            Error = ex.Message;
            Detail = ex.Source;
        }
        [DataMember]
        public String Error { get; set; }
        [DataMember]
        public String Detail { get; set; }
    }

Answer 4

ErrorMessage 类是什么样的？

不要将 StatusMessage 字段用于机器可读数据 - 请参阅https://www.rfc-editor.org/rfc/rfc2616#section-6.1.1。

另外，“http 正文现在有文本‘无法加载源：http://localhost:7000/bla..’而不是实际的 JSON 数据..”可能没问题——文字字符串是 JSON数据如果我没记错的话。