构建WCF的消息代理

         有时在项目中，由于部署的原因。我们需要对原来的WCF Service做一个代理，实现消息完全转发。WCF中我们可以这样实现，假设有这样的Service

    [ServiceContract]
    public interface IMath
    {
        [OperationContract]
        double Add(double A, double B);
    }

实现：

    public class Math : IMath
    {
        public double Add(double A, double B)
        {
            return A + B;
        }
    }

然后我们Host一个service, address是 http://localhost:24258/Math.svc ，然后我们测试它：

        [TestMethod]
        public void TestMessageForSVCHost()
        {
            using (var myChannelFactory = new ChannelFactory<IMath>(new BasicHttpBinding(), "http://localhost:24258/Math.svc"))
            {
                // Create a channel.
                IMath wcfClient1 = myChannelFactory.CreateChannel();
                var s = wcfClient1.Add(1, 234);
                Console.WriteLine(s.ToString());
                ((IClientChannel)wcfClient1).Close();

                myChannelFactory.Close();

                Assert.AreEqual(235, s);
            }
        }

现在我们来增加一个Proxy Interface:

    using System.ServiceModel;
    using System.ServiceModel.Channels;

    /// <summary>
    /// The i pass through service.
    /// </summary>
    [ServiceContract]
    public interface IPassThroughService
    {
        #region Public Methods

        /// <summary>
        /// The process message.
        /// </summary>
        /// <param name="message">
        /// The message.
        /// </param>
        /// <returns>a meeage
        /// </returns>
        [OperationContract(Action = "*", ReplyAction = "*")]
        Message ProcessMessage(Message message);

        #endregion
    }

实现：

    using System;
    using System.ServiceModel;
    using System.ServiceModel.Channels;

    /// <summary>
    /// PassThroughService class
    /// </summary>
    public class PassThroughService : IPassThroughService
    {
        /// <summary>
        /// Processes the message.
        /// </summary>
        /// <param name="requestMessage">The request message.</param>
        /// <returns>response Message</returns>
        public Message ProcessMessage(Message requestMessage)
        {
            using (var factory = new ChannelFactory<IPassThroughService>("testserver"))
            {
                IPassThroughService proxy = factory.CreateChannel();

                using (proxy as IDisposable)
                {
                    var responseMessag = proxy.ProcessMessage(requestMessage);
                    return responseMessag;
                }
            }
        }
    }

然后在代理WCF项目，配制节是这样的：

  <system.serviceModel>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->
          <serviceMetadata httpGetEnabled="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>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
    <client>
      <!-- Note: contract use another service contact -->
      <endpoint name="testserver" address="http://localhost:24258/Math.svc" binding="basicHttpBinding"
                 contract="ProxyWCFService.IPassThroughService"/>
    </client>
  </system.serviceModel>

注意第15行代码，我们指定了是我们目标Service address，而Contact则是 IPassThroughService, ProxyWCFService是Namespace.

然后我们Host这个代理Service, 到这个address  http://localhost:30096/PassThroughService.svc ，此时你查询的WDSL是这样的：

<?xml version="1.0" encoding="utf-8"?>
<wsdl:definitions name="PassThroughService" targetNamespace="http://tempuri.org/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/" xmlns:tns="http://tempuri.org/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy" xmlns:wsap="http://schemas.xmlsoap.org/ws/2004/08/addressing/policy" xmlns:wsaw="http://www.w3.org/2006/05/addressing/wsdl" xmlns:msc="http://schemas.microsoft.com/ws/2005/12/wsdl/contract" xmlns:wsa10="http://www.w3.org/2005/08/addressing" xmlns:wsx="http://schemas.xmlsoap.org/ws/2004/09/mex" xmlns:wsam="http://www.w3.org/2007/05/addressing/metadata">
  <wsdl:types/>
  <wsdl:portType name="IPassThroughService"/>
  <wsdl:binding name="BasicHttpBinding_IPassThroughService" type="tns:IPassThroughService">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>
  </wsdl:binding>
  <wsdl:service name="PassThroughService">
    <wsdl:port name="BasicHttpBinding_IPassThroughService" binding="tns:BasicHttpBinding_IPassThroughService">
      <soap:address location="http://localhost:30096/PassThroughService.svc"/>
    </wsdl:port>
  </wsdl:service>
</wsdl:definitions>

接着我们来看UnitTest:

        [TestMethod]
        public void TestCilentWithProxyMessage()
        {
            using (var myChannelFactory = new ChannelFactory<IMath>(new BasicHttpBinding(), "http://localhost:30096/PassThroughService.svc"))
            {
                // Create a channel.
                IMath wcfClient1 = myChannelFactory.CreateChannel();
                var s = wcfClient1.Add(1, 234);
                Console.WriteLine(s.ToString());
                ((IClientChannel)wcfClient1).Close();
                myChannelFactory.Close();

                //assert
                Assert.AreEqual(235, s);
            }
        }

你可以DEBUG，在var responseMessag = proxy.ProcessMessage(requestMessage); 代码，可以看到Request与Response Message 文本:

Request:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header>
    <To s:mustUnderstand="1" xmlns="http://schemas.microsoft.com/ws/2005/05/addressing/none">http://localhost:30096/PassThroughService.svc</To>
    <Action s:mustUnderstand="1" xmlns="http://schemas.microsoft.com/ws/2005/05/addressing/none">http://tempuri.org/IMath/Add</Action>
  </s:Header>
  <s:Body>
    <Add xmlns="http://tempuri.org/">
      <A>1</A>
      <B>234</B>
    </Add>
  </s:Body>
</s:Envelope>

Response:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header />
  <s:Body>
    <AddResponse xmlns="http://tempuri.org/">
      <AddResult>235</AddResult>
    </AddResponse>
  </s:Body>
</s:Envelope>

从这里我们可以看到这是完整的消息包，所以使用这个代理Service，拦截消息体后，还可以做一些其它TASK。例如，存储，过滤等。

希望这篇POST对您开发WCF有帮助。

作者：Petter Liu
出处：http://www.cnblogs.com/wintersun/
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该文章也同时发布在我的独立博客中-Petter Liu Blog。