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。捕获常规异常时,我的自定义类型按预期返回,但ContentType标头不正确。
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 Unauthorized http状态代码时,消息正文将被覆盖为默认类型,但ContentType标头应该是它应该的样本。
HTTP/1.1 401 Unauthorized
Content-Type: application/json;
...
{"Message":"Authentication failed.","StackTrace":null,"ExceptionType":"System.InvalidOperationException"}
显然这里出了点问题,但我不确定是什么。
如何实现IErrorHandler,使其在json中使用正确的标题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
这是我想要返回的对象。我的应用程序中的所有其他对象都继承自此对象。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实施:
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中:
<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,这是一些深埋的.Net恶作剧的结果。我选择实现IErrorHandler,以便我可以捕获任何其他可能无法处理的异常。
参考:
https://msdn.microsoft.com/en-us/library/system.servicemodel.dispatcher.ierrorhandler(v=vs.100).aspx
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?
答案 0 :(得分:0)
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,请按照您希望的方式手动构建肥皂故障或响应。
如果没有,则表示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,一个简单的方法是添加额外的HttpModule来自定义或映射响应。或者您可以尝试在通道堆栈中自定义编码器。
答案 1 :(得分:0)
根据您编写的内容,您将在服务实现的构造函数中引发异常。因为WCF使用反射来创建服务实现,除非您的服务是Singleton,否则您将获得TargetInvocationException。
示例(使用LINQPad):
void Main()
{
try
{
Activator.CreateInstance(typeof(Foo));
}
catch(Exception e)
{
e.Message.Dump();
e.GetType().Name.Dump();
}
}
public class Foo
{
public Foo()
{
throw new AuthorizationFailedException();
}
}
public class AuthorizationFailedException : Exception
{
}
基本上,避免在构造函数中基于业务逻辑抛出异常。只有那样才能处理编程错误。
答案 2 :(得分:0)
经过几乎整整一天的努力,我发现这是由IIS设置引起的。
在IIS中的我的API项目下,在“身份验证”菜单下,我将“表单身份验证”设置为“已启用”。我关闭了这个'功能',上面的代码开始按预期工作。我发现这是由于我团队中的另一位开发人员将代码置于web.config文件中,该文件改变了IIS中的设置。具体做法是:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
...
<system.web>
<authentication mode="Forms" />
</system.web>
...
</configuration>
此外,通过使用WebOperationContext OutgoingResponse对象上的ContentType属性,我能够正确显示Content-Type标头。
// Get the outgoing response portion of the current context
var response = WebOperationContext.Current.OutgoingResponse;
// Add ContentType header that specifies we are using JSON
response.ContentType = new MediaTypeHeaderValue("application/json").ToString();