wcf Endpoint简介
WCF实际上是构建了一个框架,这个框架实现了 在互联系统中各个Application之间如何通信。使得Developers和Architect在构建分布式系统中,无需在考虑如何去实现通信相关 的问题,更加关注与系统的业务逻辑本身。而在WCF Infrastructure中,各个Application之间的通信是由Endpoint来实现的。
Endpoint的结构
Endpoint包含以下4个对象:
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Address: Address通过一个URI唯一地标识一个Endpoint,并告诉潜在的WCF service的调用者如何找到这个Endpoint。所以Address解决了Where to locate the WCF Service?
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Binding: Binding实现在Client和Service通信的所有底层细节。比如Client与Service之间传递的Message是如何编码的—— text/XML, binary,MTOM;这种Message的传递是采用的哪种Transport——TCP, Http, Named Pipe, MSMQ; 以及采用怎样的机制解决Secure Messaging的问题——SSL,Message Level Security。所以Binding解决的是How to communicate with service?
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Contract: Contract的主要的作用是暴露某个WCF Service所提供的所有有效的Functionality。从Message Exchange的层面上讲,Contract实际上是抱每个Operation转化成为相对应的Message Exchange Pattern——MEP(Request/Response; One-way; Duplex)。所以Contract解决的是What functionalities do the Service provide?
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Behavior: Behavior的主要作用是定制Endpoint在运行时的一些必要的Behavior。比如Service 回调Client的Timeout;Client采用的Credential type;以及是否支持Transaction等。
当我们Host一个WCF Service的时候,我们必须给他定义一个或多个Endpoint,然后service通过这个定义的Endpoint进行监听来自Client端的请 求。当我们的Application需要调用这个Service的时候,因为Client 和Service是通过Endpoint的进行通信的, 所以我们必须为我们的Application定义Client端的Endpoint。只有当Client的Endpoint和Service端某个 Endpoint相互匹配(Service端可以为一个Service定义多个Endpoint),Client端的请求才能被Service端监听到。 也就是说,我们只有在Client具有一个与Service端完全匹配的Endpoint,我们才能调用这个Service。而这种匹配是比较严格的,比 如从匹配Address方面,Client端和Service端的Endpoint Address不仅仅在URI上要完全匹配Service, 他们的Headers也需要相互匹配。对于Binding, 一般地,Client需要有一个与Service端完全一样的Binding,他们之间才能通信。
Sample
首先给一个Sample,以便我们对在WCF Service Aplication中如何定义Endpoint有一个感性的认识。整个Solution的结构参照下图,我的上一篇Blog(创建一个简单的WCF程序)中有详细的介绍。你也可以通过后面的Link下载相应的Source Code(http://www.cnblogs.com/files/artech/Artech.WCFService.zip )
1. Service Contract:Artech..WCfService.Contract/ServiceContract/IGeneralCalculator.cs
using System; using System.Collections.Generic; using System.Text; using System.ServiceModel; namespace Artech.WCFService.Contract { [ServiceContract] public interface IGeneralCalculator { [OperationContract] double Add(double x, double y); } }
2. Service: Artech.WCFSerice.Service/GeneralCalculatorService.cs
using System; using System.Collections.Generic; using System.Text; using Artech.WCFService.Contract; namespace Artech.WCFService.Service { public class GeneralCalculatorService:IGeneralCalculator { IGeneralCalculator Members#region IGeneralCalculator Members public double Add(double x, double y) { return x + y; } #endregion } }
3. Hosting: Artech.WCFService.Hosting/Program.cs
using System; using System.Collections.Generic; using System.Text; using System.ServiceModel; using Artech.WCFService.Contract; using Artech.WCFService.Service; using System.ServiceModel.Description; namespace Artech.WCFService.Hosting { class Program { static void Main(string[] args) { //HostCalculatorServiceViaCode(); HostCalculatorSerivceViaConfiguration(); } /**//// <summary> /// Hosting a service using managed code without any configuraiton information. /// Please note that the related configuration data should be removed before calling the method. /// </summary> static void HostCalculatorServiceViaCode() { Uri httpBaseAddress = new Uri("http://localhost:8888/generalCalculator"); Uri tcpBaseAddress = new Uri("net.tcp://localhost:9999/generalCalculator"); using (ServiceHost calculatorSerivceHost = new ServiceHost(typeof(GeneralCalculatorService), httpBaseAddress, tcpBaseAddress)) { BasicHttpBinding httpBinding = new BasicHttpBinding(); NetTcpBinding tcpBinding = new NetTcpBinding(); calculatorSerivceHost.AddServiceEndpoint(typeof(IGeneralCalculator), httpBinding, string.Empty); calculatorSerivceHost.AddServiceEndpoint(typeof(IGeneralCalculator), tcpBinding, string.Empty); ServiceMetadataBehavior behavior = calculatorSerivceHost.Description.Behaviors.Find<ServiceMetadataBehavior>(); { if(behavior == null) { behavior = new ServiceMetadataBehavior(); behavior.HttpGetEnabled = true; calculatorSerivceHost.Description.Behaviors.Add(behavior); } else { behavior.HttpGetEnabled = true; } } calculatorSerivceHost.Opened += delegate { Console.WriteLine("Calculator Service has begun to listen "); }; calculatorSerivceHost.Open(); Console.Read(); } } static void HostCalculatorSerivceViaConfiguration() { using (ServiceHost calculatorSerivceHost = new ServiceHost(typeof(GeneralCalculatorService))) { calculatorSerivceHost.Opened += delegate { Console.WriteLine("Calculator Service has begun to listen "); }; calculatorSerivceHost.Open(); Console.Read(); } } } }
4. Service.svc: http://localhost/WCFService/ GeneralCalculatorService.svc
5. Client: Artech.WCFService.Client/ GeneralCalculatorClient.cs & Program.cs
using System; using System.Collections.Generic; using System.Text; using System.ServiceModel; using System.ServiceModel.Channels; using Artech.WCFService.Contract; namespace Artech.WCFService.Client { class GeneralCalculatorClient:ClientBase<IGeneralCalculator>,IGeneralCalculator { public GeneralCalculatorClient() : base() { } public GeneralCalculatorClient(string endpointConfigurationName) : base(endpointConfigurationName) { } public GeneralCalculatorClient(Binding binding, EndpointAddress address) : base(binding, address) { } IGeneralCalculator Members#region IGeneralCalculator Members public double Add(double x, double y) { return this.Channel.Add(x, y); } #endregion } }
using System; using System.Collections.Generic; using System.Text; using System.ServiceModel; using System.ServiceModel.Channels; using Artech.WCFService.Contract; namespace Artech.WCFService.Client { class Program { static void Main() { try { //InvocateCalclatorServiceViaCode(); InvocateCalclatorServiceViaConfiguration(); } catch (Exception ex) { Console.WriteLine(ex.Message); } Console.Read(); } static void InvocateCalclatorServiceViaCode() { Binding httpBinding = new BasicHttpBinding(); Binding tcpBinding = new NetTcpBinding(); EndpointAddress httpAddress = new EndpointAddress("http://localhost:8888/generalCalculator"); EndpointAddress tcpAddress = new EndpointAddress("net.tcp://localhost:9999/generalCalculator"); EndpointAddress httpAddress_iisHost = new EndpointAddress("http://localhost/wcfservice/GeneralCalculatorService.svc"); Console.WriteLine("Invocate self-host calculator service "); Invocate Self-host service#region Invocate Self-host service using (GeneralCalculatorClient calculator_http = new GeneralCalculatorClient(httpBinding, httpAddress)) { using (GeneralCalculatorClient calculator_tcp = new GeneralCalculatorClient(tcpBinding, tcpAddress)) { try { Console.WriteLine("Begin to invocate calculator service via http transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_http.Add(1, 2)); Console.WriteLine("Begin to invocate calculator service via tcp transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_tcp.Add(1, 2)); } catch (Exception ex) { Console.WriteLine(ex.Message); } } } #endregion Console.WriteLine("\n\nInvocate IIS-host calculator service "); Invocate IIS-host service#region Invocate IIS-host service using (GeneralCalculatorClient calculator = new GeneralCalculatorClient(httpBinding, httpAddress_iisHost)) { try { Console.WriteLine("Begin to invocate calculator service via http transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator.Add(1, 2)); } catch (Exception ex) { Console.WriteLine(ex.Message); } } #endregion } static void InvocateCalclatorServiceViaConfiguration() { Console.WriteLine("Invocate self-host calculator service "); Invocate Self-host service#region Invocate Self-host service using (GeneralCalculatorClient calculator_http = new GeneralCalculatorClient("selfHostEndpoint_http")) { using (GeneralCalculatorClient calculator_tcp = new GeneralCalculatorClient("selfHostEndpoint_tcp")) { try { Console.WriteLine("Begin to invocate calculator service via http transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_http.Add(1, 2)); Console.WriteLine("Begin to invocate calculator service via tcp transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_tcp.Add(1, 2)); } catch (Exception ex) { Console.WriteLine(ex.Message); } } } #endregion Console.WriteLine("\n\nInvocate IIS-host calculator service "); Invocate IIS-host service#region Invocate IIS-host service using (GeneralCalculatorClient calculator = new GeneralCalculatorClient("iisHostEndpoint")) { try { Console.WriteLine("Begin to invocate calculator service via http transport "); Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator.Add(1, 2)); } catch (Exception ex) { Console.WriteLine(ex.Message); } } #endregion } } }
<?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <behaviors> <serviceBehaviors> <behavior name="calculatorServieBehavior"> <serviceMetadata httpGetEnabled="true" /> </behavior> </serviceBehaviors> </behaviors> <services> <service behaviorConfiguration="calculatorServieBehavior" name="Artech.WCFService.Service.GeneralCalculatorService"> <endpoint address="" binding="basicHttpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator"> </endpoint> <endpoint address="" binding="netTcpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator" /> <host> <baseAddresses> <add baseAddress="http://localhost:8888/generalcalculator" /> <add baseAddress="net.tcp://localhost:9999/generalCalculator" /> </baseAddresses> </host> </service> </services> </system.serviceModel> </configuration>
7. IIS-Host Configuration:
<?xml version="1.0"?> <configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0"> <system.serviceModel> <behaviors> <serviceBehaviors> <behavior name="calculatorServiceBehavior"> <serviceMetadata httpGetEnabled ="true"></serviceMetadata> </behavior> </serviceBehaviors> </behaviors> <services> <service name="Artech.WCFService.Service.GeneralCalculatorService" behaviorConfiguration="calculatorServiceBehavior"> <endpoint binding="basicHttpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator"></endpoint> </service> </services> </system.serviceModel> <system.web> <compilation debug="true"> <assemblies> <add assembly="System.Security, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/> <add assembly="Microsoft.Transactions.Bridge, Version=3.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/> <add assembly="SMDiagnostics, Version=3.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> <add assembly="System.IdentityModel.Selectors, Version=3.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> <add assembly="System.DirectoryServices, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/> <add assembly="System.Web.RegularExpressions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/> <add assembly="System.Transactions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> <add assembly="System.Messaging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/> <add assembly="System.ServiceProcess, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/></assemblies></compilation> </system.web> </configuration>
8. Client configuration: Artech.WCFService.Client/App.config
<?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <client> <endpoint address="http://localhost:8888/generalCalculator" binding="basicHttpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator" name="selfHostEndpoint_http"/> <endpoint address="net.tcp://localhost:9999/generalCalculator" binding="netTcpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator" name="selfHostEndpoint_tcp"/> <endpoint address="http://localhost/wcfservice/GeneralCalculatorService.svc" binding="basicHttpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator" name="iisHostEndpoint"/> </client> </system.serviceModel> </configuration>
如何在Application中定义Endpoint
对于Self-Host的Service,绝大 部分的Endpoint相关的信息都具有两种定义方式——Managed Code 和Configuration。而对于把Service Host到IIS中的情况, Endpoint的信息一般虚拟根目录下的Web.Config中定义。一般的我们我们不推荐使用代码的方式Host和调用Service,这主要是基于 以下的理由。首先我们开发的环境往往与部署的环境不尽相同,才用configuration的方式是的我们可以在部署的时候通过修改配置文件以适应新的需 要。其次,对于不要出现的新的需要,比如对于一个原来只供Internet内部使用的Service,我们一般会定义一个基于TCP的Endpoint, 现在出现来自于Internet的潜在用户,我们只需要通过修改Config文件的方式为这个Service添加一个新的基于Http的Endpoint 就可以了。 把Endpoint的信息写在config文件中的优势在于,修改config文件的内容是不需要重新编译和重新部署的。相应的定义方式清参照以上的 Sample。
下面我们来看看在host 一个Service的时候,置于配置文件的信息是如何起作用的。在上面的例子中我们通过下面一段代码Host一个Serivice(对应得Service Type是GeneralCalculatorService)。
using (ServiceHost calculatorSerivceHost = new ServiceHost(typeof(GeneralCalculatorService))) { calculatorSerivceHost.Opened += delegate { Console.WriteLine("Calculator Service has begun to listen "); }; calculatorSerivceHost.Open(); Console.Read(); }
下面是Service相关的配置信息:
<services> <service behaviorConfiguration="calculatorServieBehavior" name="Artech.WCFService.Service.GeneralCalculatorService"> <endpoint address="" binding="basicHttpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator"> </endpoint> <endpoint address="" binding="netTcpBinding" contract="Artech.WCFService.Contract.IGeneralCalculator" /> <host> <baseAddresses> <add baseAddress="http://localhost:8888/generalcalculator" /> <add baseAddress="net.tcp://localhost:9999/generalCalculator" /> </baseAddresses> </host> </service> </services>
首先我们创建一个ServiceHost对象 calculatorSerivceHost,同时指定对用的Service Type 信息(typeof(GeneralCalculatorService))。WCF Infrastructure为在配置文件在Services Section寻找是否有相对用的service定义。在这个例子中,他会找到一个name属性为 Artech.WCFService.Service.GeneralCalculatorService的Service。然后他会根据定义在 Service中的Endpoint定义为calculatorSerivceHost添加相应的Endpoint。 如果有对应的Endpoint Behavior设置存在于配置文件中,这些Behavior也会设置到改Endpoint中。最后调用Open方 法,calculatorSerivceHost开始监听来自Client端的请求。
Address
每一个Endpoint都必须有一个 Address,Address定位和唯一标志一个Endpoint。在Managed code 中,Address由System.ServiceModel.EndpointAddress对象来表示。下面是一个Adress的结构:
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URI:指定的Endpoint的Location。URI对于Endpoint是必须的。
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Identity:当另一个Endpoint与此Endpoint进行消息交互时,可以获取该Identity来Authenticate正在与之进行消息交互的Endpoint是否是它所希望的。Identity对于endpoint是可选的。
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Headers:Address可以包含一些可选的Headers, 这些header最终会加到相应的Soap Message的Header中。Header存放的多为Address相关的信息,用于进行Addressing Filter。
Address的主要作用就是同过Uri为 Service提供一个监听Address。但在某些特殊的场景中,我们可以借助Address的Headers提供一些扩展的功能。在大多数的情况下 Client可以直接访问Service,换句话说,如果我们把Message 传递的路径看成是以系列连续的节点(Node)的话,Message直接从Client所在的节点(Node)传递到最终的Service的节点。但在某 些情况下,考虑的实现负载平衡,安全验证等因素,我们需要在Client和最终的Service之间加入一些中间节点(Intermediaries), 这些中间节点可以在Message到达最终Service Node之前作一些工作,比如为了实现负载平衡,它可以把Message Request分流到不同的节点——Routing;为了在Message达到最终Node之前,验证Client是否是一个合法的请求,他可以根据 Message存储的Credential的信息验证该请求——Authentication。
这些Intermediaries操作的一般不会是Message Body的内容(大多数情况下他们已经被加密),而是Message Header内容。他们可以修改Header的内容,也可以加入一些新的Header。所以为了实现Routing,我们需要在Message加入一些 Addressing相关的内容,为了实现Authentication我们需要加入Client Credential的信息, 而这些信息都放在Header中。实际上你可以把很多内容加到Header中。
我们可以通过config文件加入这些Header:
<service behaviorConfiguration="calculatorServieBehavior" name="Artech.WCFService.Service.DuplexCalculatorService"> <endpoint binding="wsDualHttpBinding" contract="Artech.WCFService.Contract.IDuplexCalculator"> <headers> <role>admin</role> </headers> </endpoint> <host> <baseAddresses> <add baseAddress="http://localhost:7777/DuplexCalculator" /> </baseAddresses> </host> </service>
<client> <endpoint address="http://localhost/WCFService/SessionfulCalculatorService.svc" binding="wsHttpBinding" bindingConfiguration="" contract="Artech.WCFService.Contract.ISessionfulCalculator" > <headers> <role>admin</role> </headers> </endpoint> </client>
Binding
WCF,顾名思义就是实现了分布式系统中各 Application之间的Communication的问题。上面我们说过, Client和Service之间的通信完全有他们各自的Endpoint的担当。Address解决了寻址的问题,通过Address,Client知 道在哪里可以找到它所希望的Service。但是知道了地址,只是实现的通信的第一步。
对于一个基于SOA的分布式系统来说,各 Application之间的通信是通过Message Exchange来实现的。如何实现在各个Application之间 进行Message的交互,首先需要考虑的是采用怎样的Transport,是采用Http呢,还是采用TCP或是其他,比如Named Pipe、MSMQ。其次需要考虑的是Message应该采取怎样的编码,是text/XML呢,还是Binary,或是MTOM;此外,对于一个企业级 的分布式应用,Security与Robustness是我们必须考虑的问题——我们应该采用Transport Level的Security(SSL)还是Message Level的Security;如何确保我们的Message的传递是可靠的(Reliable Messaging); 如何把在各application中执行的操作纳入同一个事物中(Transaction)。而这一些都是Binding需要解决的问题。所以我们可以说 Binding实现了Client和Service通信的所有底层细节。
在WCF中,Binding一个Binding Element的集合,每个Binding Element解决Communication的某一个方面。所有的Binding Element大体上可以分为以下3类:
1. Transport Binding Element:实现Communication的Transport选取,每个Binding必须包含一格Transport Element。
2. Encoding Binding Element:解决传递数据的编码的问题,每个Binding必须包含一个Encoding Element,一般由Transport Binding Element来提供。
3. Protocol Binding Element:解决Security,Reliable Messaging和Transaction的问题。
下边这个表格列出了Binding中的各个层次结构。
Layer |
Options |
Required |
Transactions |
TransactionFlowBindingElement |
No |
Reliability |
ReliableSessionBindingElement |
No |
Security |
SecurityBindingElement |
No |
Encoding |
Text, Binary, MTOM, Custom |
Yes |
Transport |
TCP, Named Pipes, HTTP, HTTPS, MSMQ, Custom |
Yes |
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