WCF – MetaData
WCF的metadata描述了客户端如何同服务进行交互。通过metadata,我们可以利用一些工具生成proxy代码,比如SvcUtil.exe,客户端编程基本上是基于这些proxy的
服务有两种方案可以发布自己的元数据。一种是基于HTTP-GET协议提供元数据;另一种则为元数据交换方式,它往往使用一个专门的终结点,称之为元数据交换终结点。元数据交换终结点与其它终结点相似,仍然包含了地址、绑定与契约,但是使用的服务契约为WCF提供的接口IMetadataExchange。
实际上,这两种发布元数据的方式代表了它使用了两种不同的标准协议,前者为HTTP/GET请求,后者为WS-MetadataExchange(MEX)。在WCF,以MetadataExchangeClientMode枚举类型表示这两种元数据交换模式:
public enum MetadataExchangeClientMode { MetadataExchange, HttpGet }
1. HTTP-GET
起用了这种方式的metadata发布,客户端可以通过浏览器察看并确认元数据。同前面几篇文章介绍的一样,启用方法也是2种:编成和配置。
配置元数据发布是通过添加ServiceBehavior来实现的,例子如下:
<system.serviceModel> <services> <service name="MyNamespace.MyService" behaviroConfiguration="MEXGET"> <endpoint contract = "MyNamespace.IMyService" binding = "wsHttpBinding" address = "http://localhost:8000/MyService" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="MEXGET"> <serviceMetadata httpGetEnabled="true"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel>
编程方式:
ServiceHost host = new ServiceHost(typeof(MyService)); ServiceMetadataBehavior metadataBehavior = host.Description.Behaviors.Find<ServiceMetadataBehavior>(); if(metadataBehavior == null) { metadataBehavior = new ServiceMetadataBehavior(); metadataBehavior.HttpGetEnabled = true; host.Description.Behaviors.Add(metadataBehavior); } Binding wsHttpBinding = new WSHttpBinding(); host.AddServiceEndpoint(typeof(IMyService), wsHttpBinding, new Uri("http://localhost:8086/MyService/")); host.Open(); ... host.Close();
2. Metadata-Exchange
这种方式是通过定义特定的endpoint的方式来发布元数据,这种endpoint被称作元数据终结点或者MEX终结点。WCF为MEX终结点的ABC分别给出了各自的定义。
- A - 类似于普通的endpoint地址。
- B - 基于http, https, tcp和icp协议的binding。例如,mexTcpBinding, mexNamePipeBinding, mexHttpBinding….
- C - IMetadataExchange接口。其实现由WCF自动提供。
以下是一个配置Mex endpoint的例子:
<system.serviceModel> <services> <service name="MyNamespace.MyService" behaviroConfiguration="MEX"> <endpoint contract = "MyNamespace.IMyService" binding = "wsHttpBinding" address = "http://localhost:8000/MyService" /> <endpoint contract = "IMetadataExchange" binding = "mexHttpBinding" address = "http://localhost:8000/MEX" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="MEX"> <serviceMetadata/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel>
同样可以通过编程的方式来启动mex endpoint:
BindingElement bindingElement = new TcpTransportBindingElement(); CustomBinding binding = new CustomBinding(bindingElement); Uri tcpBaseAddress = new Uri("net.tcp://localhost:9000"); ServiceHost host = new ServiceHost(typeof(MyService), tcpBaseAddress); if(metadataBehavior == null) { metadataBehavior = new ServiceMetadataBehavior(); host.Description.Behaviors.Add(metadataBehavior); } host.AddServiceEndpoint(typeof(IMetadataExchange), binding, "MEX"); host.Open(); ... host.Close();