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。
http://tech.ddvip.com/2008-10/122483707382615.html
endpoint 是一个存在的location
Endpoint包含以下4个对象:
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?
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?
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实际上是将每个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?
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。
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([原创]我的WCF之旅(1):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://tech.ddvip.com/%22http://localhost:8888/generalCalculator/%22");
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
<%@ ServiceHost Language="C#" Debug="true" Service="Artech.WCFService.Service.GeneralCalculatorService" %>
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://tech.ddvip.com/%22http://localhost:8888/generalCalculator/%22");
EndpointAddress tcpAddress = new EndpointAddress("net.tcp://localhost:9999/generalCalculator");
EndpointAddress httpAddress_iisHost = new EndpointAddress("http://tech.ddvip.com/%22http://localhost/wcfservice/GeneralCalculatorService.svc/%22");
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("nnInvocate 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("nnInvocate 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
}
}
}
6. Self-Hosting Configuration: Artech.WCFService.Hosting/App.config
<?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://tech.ddvip.com/%22http://localhost:8888/generalcalculator/%22" />
<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://tech.ddvip.com/%22http://schemas.microsoft.com/.NetConfiguration/v2.0/%22">
<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://tech.ddvip.com/%22http://localhost:8888/generalCalculator/%22" 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://tech.ddvip.com/%22http://localhost/wcfservice/GeneralCalculatorService.svc/%22" 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://tech.ddvip.com/%22http://localhost:8888/generalcalculator/%22" />
<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:
URI:指定的Endpoint的Location。URI对于Endpoint是必须的。
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。
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://tech.ddvip.com/%22http://localhost:7777/DuplexCalculator/%22" />
</baseAddresses>
</host>
</service>
<client>
<endpoint address="http://tech.ddvip.com/%22http://localhost/WCFService/SessionfulCalculatorService.svc/%22"
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 |
WCF提供了一个框架/平台来构建分布的互联系统,WCF是SOA的,是面向服务的。但一个Service必须至少包含一个Endpoint,否则,试想一下,客户端连到哪里来获得一个Service?一个服务(Service)必须告诉外部在某个Endpoint提供什么和沟通什么。换句话说:“服务就是: 在某个地方、使用某种通讯协议、传输某种数据类型的消息”。
客户只能通过服务的Endpoint来访问服务。每个Endpoint必须包含地址、绑定和协议(契约), host 进程会提供 Endpoint 供客户端调用。一个服务至少包含一个Endpoint,可以有多个Endpoint,多个绑定和多个契约。多个 Endpoint 可以共享相同的绑定和契约,每个服务又可以提供多个 Endpoint 供客户端掉用。每个Endpoint用唯一的地址(Address)来区分于其它的Endpoint,绑定指定了服务与外部通讯的方式( 例如 NetTcp, MSMQ等等),而契约指定了消息格式、Endpoint会发生的行为具体提供什么服务,Service behaviour可以控制服务的运行时特性( 例如 线程问题,service实例管理等)。当服务收到一条消息,服务开始执行。一个服务的描述和实现代码的CLR runtime instance被创建。WCF运行时(WCF Runtime)控制消息的格式化,消息的收发等等。
[OperationBehavior] 特性
[OperationBehavior] 特性
WCF Contract 三种基本契约类型: