WCF技术剖析之二十九：换种不同的方式调用WCF服务[提供源代码下载]

蒋金楠

发布于 2018-01-16 10:01:21

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我们有两种典型的WCF调用方式：通过SvcUtil.exe（或者添加Web引用）导入发布的服务元数据生成服务代理相关的代码和配置；通过ChannelFactory<TChannel>创建服务代理对象。在这篇文章中，我们采用一种独特的方式进行服务的调用。从本质上讲，我们只要能够创建于服务端相匹配的终结点，就能够实现正常的服务调用。在WCF客户端元数据架构体系中，利用MetadataExchangeClient可以获取服务的元数据，而利用MetadataImporter将获取的元数据导入成ServiceEndpoint对象。在本例中，我们将利用这两个组件定义了一个独特的服务调用的简单的例子，相信可以帮助读者进一步加深对WCF元数据框架体系的理解。 (Source从这里下载)

我们依然采用我们熟悉的计算服务的例子，下面是该服务相应的服务契约、服务类型的定义和寄宿该服务采用的配置。

   1: using System.ServiceModel;
   2: namespace Artech.ServiceInvocationViaMetadata.Contracts
   3: {
   4:     [ServiceContract(Namespace = "http://www.artech.com/")]
   5:     public interface ICalculator
   6:     {
   7:         [OperationContract]
   8:         double Add(double x, double y);
   9:     }
  10: }

服务类型：

   1: using System.ServiceModel;
   2: using Artech.ServiceInvocationViaMetadata.Contracts;
   3:  
   4: namespace Artech.ServiceInvocationViaMetadata.Services
   5: {
   6:     public class CalculatorService : ICalculator
   7:     {
   8:         public double Add(double x, double y)
   9:         {
  10:             return x + y;
  11:         }
  12:     }
  13: }

配置：

   1: <?xml version="1.0" encoding="utf-8" ?>
   2: <configuration>
   3:     <system.serviceModel>
   4:         <behaviors>
   5:             <serviceBehaviors>
   6:                 <behavior name="mexBehavior">
   7:                     <serviceMetadata />
   8:                 </behavior>
   9:             </serviceBehaviors>
  10:         </behaviors>
  11:         <services>
  12:             <service behaviorConfiguration="mexBehavior" name="Artech.ServiceInvocationViaMetadata.Services.CalculatorService">
  13:                 <endpoint address="http://127.0.0.1:3721/calculatorservice" binding="ws2007HttpBinding" contract="Artech.ServiceInvocationViaMetadata.Contracts.ICalculator" />
  14:                 <endpoint address="http://127.0.0.1:3721/calculatorservice/mex" binding="mexHttpBinding" contract="IMetadataExchange" />
  15:             </service>
  16:         </services>
  17:     </system.serviceModel>
  18: </configuration>

从上面的配置我们可以看到，服务的元数据通过WS-MEX模式发布出来，发布的地址和采用的MEX绑定分别为：http://127.0.0.1:3721/calculatorservice/mex和mexHttpBinding。

接下来，我们就可以通过下面的方式对该服务进行调用了。我们先创建MetadataExchangeClient对象并利用它获取包含元数据的MetadataSet对象，并利用该对象创建WsdlImporter对象。接下来，我们将基于ICalculator接口的服务契约添加到该WsdlImporter的已知契约列表中，调用ImportAllEndpoints方法得到导入的ServiceEndpoint列表。最后根据导出的ServiceEndpoint对象创建ChannelFactory<ICalculator>对象，并创建服务代理进行服务调用。

   1: sing System;
   2: using System.ServiceModel;
   3: using System.ServiceModel.Description;
   4: using System.Xml;
   5: using Artech.ServiceInvocationViaMetadata.Contracts;
   6: namespace Artech.ServiceInvocationViaMetadata.Client
   7: {
   8:     class Program
   9:     {
  10:         static void Main(string[] args)
  11:         {
  12:             MetadataExchangeClient metadataExchangeClient = new MetadataExchangeClient(MetadataExchangeBindings.CreateMexHttpBinding());
  13:             MetadataSet metadata = metadataExchangeClient.GetMetadata(new EndpointAddress("http://127.0.0.1:3721/calculatorservice/mex"));
  14:             WsdlImporter wsdlImporter = new WsdlImporter(metadata);
  15:             //添加已知契约类型
  16:             ContractDescription contract = ContractDescription.GetContract(typeof(ICalculator));
  17:             wsdlImporter.KnownContracts.Add(new XmlQualifiedName(contract.Name, contract.Namespace), contract);
  18:             ServiceEndpointCollection endpoints = wsdlImporter.ImportAllEndpoints();
  19:             using (ChannelFactory<ICalculator> channelFactory = new ChannelFactory<ICalculator>(endpoints[0]))
  20:             {
  21:                 ICalculator calculator = channelFactory.CreateChannel();
  22:                 using (calculator as IDisposable)
  23:                 {
  24:                     try
  25:                     {
  26:                         Console.WriteLine("x + y = {2} when x = {0} and y = {1}", 1, 2, calculator.Add(1, 2));
  27:                     }
  28:                     catch(TimeoutException)
  29:                     {
  30:                         (calculator as ICommunicationObject).Abort();
  31:                         throw;
  32:                     }
  33:                     catch(CommunicationException)
  34:                     {
  35:                         (calculator as ICommunicationObject).Abort();
  36:                         throw;
  37:                     }
  38:                 }
  39:             }
  40:             Console.Read();
  41:         }
  42:     }
  43: }