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WCF: provide generic FaultException in IErrorHandler

由 你说的曾经没有我的故事 提交于 2019-12-03 13:32:08

I don't have any experience with WSCF.blue therefore I tried to make an example application to demonstrate a working scenario using standard WCF client and server. Maybe it will help you find the missing connections to make your scenario work.

I used your BusinessRuleFaultExceptionType with Code and Reason properties. The BusinessRuleFaultExceptionType is a WCF fault contract.

I was a bit lazy and implemented all the code in a single console application. Wcf client uses the same Datacontracts and ICalculator interface as the Wcf service. Sorry for the code. It will be a long post.

First the Datacontracts and service Interface

using System;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;

[ServiceContract(Namespace = "http://UE.ServiceModel.Samples")]
public interface ICalculator
{
    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Add(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Subtract(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Multiply(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Divide(double n1, double n2);
}

/// <summary>
/// General fault structure. 
/// </summary>
[DataContract(Namespace = "http://someurl.temp")]
public sealed class BusinessRuleFaultExceptionType
{
    [DataMember]
    public int Code { get; set; }

    [DataMember]
    public string Reason { get; set; }
}

Now, the service implementation:

[ErrorBehavior(typeof(MyErrorHandler))]
public class CalculatorService : ICalculator
{
    public double Add(double n1, double n2)
    {
        double result = n1 + n2;
        Console.WriteLine("Received Add({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        throw new ArgumentException("My exception");
        return result;
    }

    public double Subtract(double n1, double n2)
    {
        double result = n1 - n2;
        Console.WriteLine("Received Subtract({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }

    public double Multiply(double n1, double n2)
    {
        double result = n1 * n2;
        Console.WriteLine("Received Multiply({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }

    public double Divide(double n1, double n2)
    {
        double result = n1 / n2;
        Console.WriteLine("Received Divide({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }
}

And client implementation:

public class Client : ClientBase<ICalculator>, ICalculator
{

    public double Add(double n1, double n2)
    {
        try
        {
            return base.Channel.Add(n1, n2);
        }
        catch (FaultException<BusinessRuleFaultExceptionType> ex)
        {
            Console.WriteLine("This is my Code: {0}. This is the reason: {1}", ex.Detail.Code, ex.Detail.Reason);
        }
        catch (Exception ex)
        {
            throw;
        }
        return 0;
    }

    public double Subtract(double n1, double n2)
    {
        throw new NotImplementedException();
    }

    public double Multiply(double n1, double n2)
    {
        throw new NotImplementedException();
    }

    public double Divide(double n1, double n2)
    {
        throw new NotImplementedException();
    }
}

Main program to demonstrate this example

internal class Program
{
    private static void Main(string[] args)
    {
        ServiceHost myServiceHost = new ServiceHost(typeof(CalculatorService));

        // Open the ServiceHostBase to create listeners and start listening for messages.
        myServiceHost.Open();

        // The service can now be accessed.
        Console.WriteLine("The service is ready.");
        Console.WriteLine("Press <ENTER> to terminate service.");
        Console.WriteLine();

        Console.ReadLine();

        Console.WriteLine("Sending data from client to service.");
        Client c = new Client();
        var res = c.Add(1, 2);

        Console.ReadLine();
    }

}

Implementation of error handling:

/// <summary>
/// Helper class for exception repackaging.
/// </summary>
internal class MyExceptionHandler
{
    /// <summary>
    /// Handles thrown exception into internal exceptions that are being sent over to client.
    /// </summary>
    /// <param name="error">Exception thrown.</param>
    /// <returns>Repackaged exception.</returns>
    internal static Exception HandleError(Exception error)
    {
        // could do something here.
        return error;
    }
}

#region Behaviour
/// <summary>
/// Control the fault message returned to the caller and optionally perform custom error processing such as logging.
/// </summary>
public sealed class MyErrorHandler : IErrorHandler
{
    /// <summary>
    /// Provide a fault. The Message fault parameter can be replaced, or set to null to suppress reporting a fault.
    /// </summary>
    /// <param name="error">The <see cref="Exception"/> object thrown in the course of the service operation.</param>
    /// <param name="version">The SOAP version of the message.</param>
    /// <param name="fault">The <see cref="System.ServiceModel.Channels.Message"/> object that is returned to the client, or service, in the duplex case.</param>
    public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
    {
        //If it's a FaultException already, then we have nothing to do
        if (error is FaultException)
            return;

        error = MyExceptionHandler.HandleError(error);

        var serviceDebug = OperationContext.Current.EndpointDispatcher.ChannelDispatcher.IncludeExceptionDetailInFaults;

        BusinessRuleFaultExceptionType f = new BusinessRuleFaultExceptionType
        {
            Code = -100,
            Reason = "xxx"
        };

        FaultException<BusinessRuleFaultExceptionType> faultException = new FaultException<BusinessRuleFaultExceptionType>(f, error.Message);
        MessageFault faultMessage = faultException.CreateMessageFault();
        fault = Message.CreateMessage(version, faultMessage, faultException.Action);
    }

    /// <summary>
    /// Enables error-related processing and returns a value that indicates whether the dispatcher aborts the session and the instance context in certain cases.
    /// </summary>
    /// <param name="error">The exception thrown during processing.</param>
    /// <returns>true if Windows Communication Foundation (WCF) should not abort the session (if there is one) and instance context if the instance context is not Single; otherwise, false. The default is false.</returns>
    public bool HandleError(Exception error)
    {
        // could use some logger like Nlog but as an example it will do.
        Console.WriteLine("Error occured. {0}", error);

        return true;
    }
}

/// <summary>
/// This attribute is used to install a custom error handler for a service
/// </summary>
public sealed class ErrorBehaviorAttribute : Attribute, IServiceBehavior
{
    /// <summary>
    /// Type of component to which this error handled should be bound
    /// </summary>
    private readonly Type errorHandlerType;

    /// <summary>
    /// Initializes a new instance of the ErrorBehaviorAttribute class.
    /// </summary>
    /// <param name="errorHandlerType">Type of component to which this error handled should be bound</param>
    public ErrorBehaviorAttribute(Type errorHandlerType)
    {
        this.errorHandlerType = errorHandlerType;
    }

    /// <summary>
    /// Type of component to which this error handled should be bound
    /// </summary>
    public Type ErrorHandlerType
    {
        get { return errorHandlerType; }
    }

    /// <summary>
    /// Provides the ability to inspect the service host and the service description to confirm that the service can run successfully.
    /// </summary>
    /// <param name="description">
    /// <para>Type: <see cref="System.ServiceModel.Description.ServiceDescription"/></para>
    /// <para>The service description.</para>
    /// </param>
    /// <param name="serviceHostBase">
    /// <para>Type: <see cref="System.ServiceModel.ServiceHostBase"/></para>
    /// <para>The service host that is currently being constructed.</para>
    /// </param>
    void IServiceBehavior.Validate(ServiceDescription description, ServiceHostBase serviceHostBase)
    {
    }

    /// <summary>
    /// Provides the ability to pass custom data to binding elements to support the contract implementation.
    /// </summary>
    /// <param name="description">
    /// <para>Type: <see cref="System.ServiceModel.Description.ServiceDescription"/></para>
    /// <para>The service description.</para>
    /// </param>
    /// <param name="serviceHostBase">
    /// <para>Type: <see cref="System.ServiceModel.ServiceHostBase"/></para>
    /// <para>The host of the service.</para>
    /// </param>
    /// <param name="endpoints">
    /// <para>Type: <see cref="System.Collections.ObjectModel.Collection&lt;ServiceEndpoint&gt;"/></para>
    /// <para>The service endpoints.</para>
    /// </param>
    /// <param name="parameters">
    /// <para>Type: <see cref="System.ServiceModel.Channels.BindingParameterCollection"/></para>
    /// <para>Custom objects to which binding elements have access.</para>
    /// </param>
    void IServiceBehavior.AddBindingParameters(ServiceDescription description, ServiceHostBase serviceHostBase, System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints, BindingParameterCollection parameters)
    {
    }

    /// <summary>
    /// Provides the ability to change run-time property values or insert custom extension objects such as error handlers, message or parameter interceptors, security extensions, and other custom extension objects.
    /// </summary>
    /// <param name="description">
    /// <para>Type: <see cref="System.ServiceModel.Description.ServiceDescription"/></para>
    /// <para>The service description.</para>
    /// </param>
    /// <param name="serviceHostBase">
    /// <para>Type: <see cref="System.ServiceModel.ServiceHostBase"/></para>
    /// <para>The host that is currently being built.</para>
    /// </param>
    void IServiceBehavior.ApplyDispatchBehavior(ServiceDescription description, ServiceHostBase serviceHostBase)
    {
        IErrorHandler errorHandler;

        try
        {
            errorHandler = (IErrorHandler)Activator.CreateInstance(errorHandlerType);
        }
        catch (MissingMethodException e)
        {
            throw new ArgumentException("The errorHandlerType specified in the ErrorBehaviorAttribute constructor must have a public empty constructor.", e);
        }
        catch (InvalidCastException e)
        {
            throw new ArgumentException("The errorHandlerType specified in the ErrorBehaviorAttribute constructor must implement System.ServiceModel.Dispatcher.IErrorHandler.", e);
        }

        foreach (ChannelDispatcherBase channelDispatcherBase in serviceHostBase.ChannelDispatchers)
        {
            ChannelDispatcher channelDispatcher = channelDispatcherBase as ChannelDispatcher;
            channelDispatcher.ErrorHandlers.Add(errorHandler);
        }
    }
}

#endregion

And app.config of my console application:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <system.serviceModel>
    <client>
      <endpoint address="http://localhost:12345/service/calc" binding="basicHttpBinding" contract="ConsoleApplication2.ICalculator" >
      </endpoint>
    </client>
    <services>
      <service name="ConsoleApplication2.CalculatorService" behaviorConfiguration="service">
        <endpoint address="http://localhost:12345/service/calc" binding="basicHttpBinding" contract="ConsoleApplication2.ICalculator" >
        </endpoint>
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:12345/service/calc" />
          </baseAddresses>
        </host>
      </service>

    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="service">
          <serviceMetadata httpGetEnabled="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
</configuration>

I used WCF test client to sent this request:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header>
    <Action s:mustUnderstand="1" xmlns="http://schemas.microsoft.com/ws/2005/05/addressing/none">http://UE.ServiceModel.Samples/ICalculator/Add</Action>
  </s:Header>
  <s:Body>
    <Add xmlns="http://UE.ServiceModel.Samples">
      <n1>0</n1>
      <n2>1</n2>
    </Add>
  </s:Body>
</s:Envelope>

and got this response:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header />
  <s:Body>
    <s:Fault>
      <faultcode>s:Client</faultcode>
      <faultstring xml:lang="sk-SK">My exception</faultstring>
      <detail>
        <BusinessRuleFaultExceptionType xmlns="http://someurl.temp" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
          <Code>-100</Code>
          <Reason>xxx</Reason>
        </BusinessRuleFaultExceptionType>
      </detail>
    </s:Fault>
  </s:Body>
</s:Envelope>

When I called 

Client c = new Client();
var res = c.Add(1, 2);

I caught FaultException<BusinessRuleFaultExceptionType> ex which I logged to console 

Console.WriteLine("This is my Code: {0}. This is the reason: {1}", ex.Detail.Code, ex.Detail.Reason);

EDIT: I have changed namespaces in BusinessRuleFaultExceptionType and set the solution to use [XmlSerializerFormat(SupportFaults = true)].

Changed interface, datacontracts and service implementation:

[ServiceContract(Namespace = "http://UE.ServiceModel.Samples")]
[XmlSerializerFormat(SupportFaults = true)]
public interface ICalculator
{
    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Add(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Subtract(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Multiply(double n1, double n2);

    [OperationContract(IsOneWay = false)]
    [FaultContract(typeof(BusinessRuleFaultExceptionType))]
    double Divide(double n1, double n2);
}

/// <summary>
/// General fault structure. 
/// </summary>
[DataContract(Name = "BusinessRuleFaultExceptionType", Namespace = "http://someurl.temp")]
[XmlType("BusinessRuleFaultExceptionType", Namespace = "http://someurl.temp")]
public sealed class BusinessRuleFaultExceptionType
{
    //[DataMember]
    [XmlElement(IsNullable = false,Namespace = "http://namespaces2.url")]
    public int Code { get; set; }

    [XmlElement(IsNullable = false, Namespace = "http://namespaces2.url")]
    public string Reason { get; set; }
}

[ErrorBehavior(typeof(MyErrorHandler))]
public class CalculatorService : ICalculator
{
    public double Add(double n1, double n2)
    {
        double result = n1 + n2;
        Console.WriteLine("Received Add({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);

        throw new FaultException<BusinessRuleFaultExceptionType>(new BusinessRuleFaultExceptionType()
        {
            Code = -100,
            Reason = "xxx"
        });
        //throw new ArgumentException("My exception");
        return result;
    }

    public double Subtract(double n1, double n2)
    {
        double result = n1 - n2;
        Console.WriteLine("Received Subtract({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }

    public double Multiply(double n1, double n2)
    {
        double result = n1 * n2;
        Console.WriteLine("Received Multiply({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }

    public double Divide(double n1, double n2)
    {
        double result = n1 / n2;
        Console.WriteLine("Received Divide({0},{1})", n1, n2);
        Console.WriteLine("Return: {0}", result);
        return result;
    }
}

I have found an article about the reasons why there are problems with using XmlSerializer in IErrorHandler. Therefore I have changed the service implementation to throw FaultException in method implementation and to not to rely on IErrorHandler.

I also found another (relatively old) article how to use XmlSerializer in IErroHandler and after some time I have made it possible to serialize even from IErrorHandler. I changed the trown exception back to ArgumentException. Here are the changes (I continued with previous example so maybe not all code and attributes are required):

[DataContract(Name = "BusinessRuleFaultExceptionType", Namespace = "http://someurl.temp")]
[XmlType("BusinessRuleFaultExceptionType", Namespace = "http://someurl.temp")]
[XmlRoot("BusinessRuleFaultExceptionType", Namespace = "http://someurl.temp")]
public sealed class BusinessRuleFaultExceptionType
{
    //[DataMember]
    [XmlElement(IsNullable = false, Namespace = "http://namespaces2.url")]
    public int Code { get; set; }

    [XmlElement(IsNullable = false, Namespace = "http://namespaces2.url")]
    public string Reason { get; set; }
}

public class XmlSerializerMessageFault : MessageFault
{
    FaultCode code;
    FaultReason reason;

    object details;

    public XmlSerializerMessageFault(FaultCode code, FaultReason reason, object details)
    {
        this.details = details;
        this.code = code;
        this.reason = reason;
    }

    public override FaultCode Code
    {
        get { return code; }
    }

    public override bool HasDetail
    {
        get { return (details != null); }
    }

    protected override void OnWriteDetailContents(System.Xml.XmlDictionaryWriter writer)
    {
        var ser = new XmlSerializer(details.GetType());
        ser.Serialize(writer, details);
        writer.Flush();
    }

    public override FaultReason Reason
    {
        get { return reason; }
    }
}

/// <summary>
/// Control the fault message returned to the caller and optionally perform custom error processing such as logging.
/// </summary>
public sealed class MyErrorHandler : IErrorHandler
{
    /// <summary>
    /// Provide a fault. The Message fault parameter can be replaced, or set to null to suppress reporting a fault.
    /// </summary>
    /// <param name="error">The <see cref="Exception"/> object thrown in the course of the service operation.</param>
    /// <param name="version">The SOAP version of the message.</param>
    /// <param name="fault">The <see cref="System.ServiceModel.Channels.Message"/> object that is returned to the client, or service, in the duplex case.</param>
    public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
    {

        BusinessRuleFaultExceptionType f = new BusinessRuleFaultExceptionType
        {
            Code = -100,
            Reason = "xxx"
        };

        // create a fault message containing our FaultContract object
        FaultException<BusinessRuleFaultExceptionType> faultException = new FaultException<BusinessRuleFaultExceptionType>(f, error.Message);
        MessageFault faultMessage = faultException.CreateMessageFault();

        var msgFault = new XmlSerializerMessageFault(faultMessage.Code, faultMessage.Reason, f);

        fault = Message.CreateMessage(version, msgFault, faultException.Action);
    }

    /// <summary>
    /// Enables error-related processing and returns a value that indicates whether the dispatcher aborts the session and the instance context in certain cases.
    /// </summary>
    /// <param name="error">The exception thrown during processing.</param>
    /// <returns>true if Windows Communication Foundation (WCF) should not abort the session (if there is one) and instance context if the instance context is not Single; otherwise, false. The default is false.</returns>
    public bool HandleError(Exception error)
    {
        // could use some logger like Nlog but as an example it will do.
        Console.WriteLine("Error occured. {0}", error);

        return true;
    }
}

In both cases the serialized fault was:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header />
  <s:Body>
    <s:Fault>
      <faultcode>s:Client</faultcode>
      <faultstring xml:lang="sk-SK">My exception</faultstring>
      <detail>
        <BusinessRuleFaultExceptionType xmlns="http://someurl.temp" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
          <Code xmlns="http://namespaces2.url">-100</Code>
          <Reason xmlns="http://namespaces2.url">xxx</Reason>
        </BusinessRuleFaultExceptionType>
      </detail>
    </s:Fault>
  </s:Body>
</s:Envelope>

I would suggest using IOperationInvoker instead of IErrorHandler. With IOperationInvoker:

  • You can use single try/catch statement. It will work as if all operations are wrapped in try/catch.
  • You won't need to manually construct resulting Message.

The implementation in your case may look like this:

public object Invoke(object instance, object[] inputs, out object[] outputs)
{
    try
    {
        return _childInvoker.Invoke(instance, inputs, out outputs);
    }
    catch (Exception error)
    {
        throw FaultExceptionFactory.CreateFaultException(error);
    }
}
标签
c#
wcf
xmlserializer
ierrorhandler
wcf-extensions
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