wcf rest ierrorhandler webfaultexception

Question

我有一个WCF4REST服务，它将由一个java客户端和一个c# mvc3客户端使用。响应内容需要作为json返回。

我希望能够以一致的方式将任何异常/故障返回给客户。我读到应该使用WebFaultException，实际上它工作得很好。

但是，我不想用WebFaultExceptions污染我的应用程序逻辑项目，因为它可能会被非web项目使用。

因此，我考虑了在WCF Rest服务中实现IErrorHandler来捕获任何异常，然后对于特定的异常(即ValidationException )，将异常作为错误返回到WebFaultException中。但是，这似乎不起作用，当调用form fiddler时，我得到以下Http 504响应

Fiddler ReadResponse()失败:服务器未返回对此请求的响应。

我已经将代码简化到最基本的部分，以显示我正在做的事情的本质。

public void ProvideFault(Exception error, 
                         MessageVersion version, 
                         ref Message fault)
{
    var ex = new WebFaultException<Exception>(
                                      new Exception("you can't do that"), 
                                      HttpStatusCode.Unauthorized);

    var xmf = ex.CreateMessageFault();
    fault = Message.CreateMessage(version,
                                  null,
                                  xmf,
                                 new DataContractJsonSerializer(xmf.GetType()));
}

我做错了什么？

Answer 1

以下是来自Carlos's blog的示例代码。这在过去对我很有帮助。

public class ValidationAwareErrorHandler : IErrorHandler
{
    IErrorHandler originalErrorHandler;
    public ValidationAwareErrorHandler(IErrorHandler originalErrorHandler)
    {
        this.originalErrorHandler = originalErrorHandler;
    }

    public bool HandleError(Exception error)
    {
        return error is ValidationException || this.originalErrorHandler.HandleError(error);
    }

    public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
    {
        ValidationException validationException = error as ValidationException;
        if (validationException != null)
        {
            fault = Message.CreateMessage(version, null, new ValidationErrorBodyWriter(validationException));
            HttpResponseMessageProperty prop = new HttpResponseMessageProperty();
            prop.StatusCode = HttpStatusCode.BadRequest;
            prop.Headers[HttpResponseHeader.ContentType] = "application/json; charset=utf-8";
            fault.Properties.Add(HttpResponseMessageProperty.Name, prop);
            fault.Properties.Add(WebBodyFormatMessageProperty.Name, new WebBodyFormatMessageProperty(WebContentFormat.Json));
        }
        else
        {
            this.originalErrorHandler.ProvideFault(error, version, ref fault);
        }
    }

    class ValidationErrorBodyWriter : BodyWriter
    {
        private ValidationException validationException;
        Encoding utf8Encoding = new UTF8Encoding(false);

        public ValidationErrorBodyWriter(ValidationException validationException)
            : base(true)
        {
            this.validationException = validationException;
        }

        protected override void OnWriteBodyContents(XmlDictionaryWriter writer)
        {
            writer.WriteStartElement("root");
            writer.WriteAttributeString("type", "object");

            writer.WriteStartElement("ErrorMessage");
            writer.WriteAttributeString("type", "string");
            writer.WriteString(this.validationException.ValidationResult.ErrorMessage);
            writer.WriteEndElement();

            writer.WriteStartElement("MemberNames");
            writer.WriteAttributeString("type", "array");
            foreach (var member in this.validationException.ValidationResult.MemberNames)
            {
                writer.WriteStartElement("item");
                writer.WriteAttributeString("type", "string");
                writer.WriteString(member);
                writer.WriteEndElement();
            }
            writer.WriteEndElement();

            writer.WriteEndElement();
        }
    }
}