WCF - Session 剖析

WCF中的Session

      WCF是MS基于SOA建立的一套在分布式环境中各个相对独立系统进行通信的构架，实现了最新的基于WS-*规范。按照SOA的原则，相对独自的业务逻辑以service的形式封装，调用者通过Messaging的方式调用Service。对于承载着某个业务功能的实现的Service应该具有上下文无关性，也就是说个构成Service的operation不应该绑定到具体的调用上下文。因为SOA的一个最大的目标就是尽可能地实现重用，只有具有上下文无关性，Service才能实现最大限度的重用。WCF中Session属于Service Contract的范畴，是一个相对抽象的概念，并在Service Contract定义中通过SessionModel参数来实现。Session的创建和结束都有来自Client端的调用来实现。

如何实现和维护Session？

      Client不能和Service进行直接交互，只能通过客户端创建的Proxy来间接地实现和service的交互，WCF在创建具体的Service Instance时会构建相关的Instance Context。我们可以制定Service的Instance context model。不同的Instance Context Mode体现为Proxy、Service 调用和Service Instance之间的对应关系，Instance Context Mode决定着不同的Session表现。在WCF中，支持以下3中不同类型的Instance Context Mode：

• PerCall：WCF为每个Serivce调用创建 一个Service Instance，调用完成后回收该Instance。

• PerSession：在Session期间的所有Service调用绑定到某一个Service Instance，Session被终止后，Service Instance被回收。

• Singleton：为具体的Service type进行Host的时候，与之对应的Service Instance就被创建出来，此后所有的Service调用都被关联到该Instance。

//IService
[ServiceContract]
 public interface ICalculatorService
 {
     [OperationContract(IsOneWay = true)]
     void PerCall(double x, double y);
     [OperationContract]
     double PerSession(double x, double y);
     [OperationContract]
     double Singleton(double x, double y);

 }
//Service
public class CalculatorService : ICalculatorService
{
    #region Constructor
    public CalculatorService()
    {
        Console.WriteLine("Create Service Instance:Current session ID is: {0}", OperationContext.Current.SessionId);
    }
    #endregion

    #region Destructor 
    ~CalculatorService()
    {
        Console.WriteLine("Destory Service Instance:Current session ID is: {0}", OperationContext.Current.SessionId);
    }
    #endregion

    #region Result
    private double _result;
    public double Result
        {
            get
            {
                return _result;
            }
        }
    #endregion

    #region ICalculator Members

    public void PerCall(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("PerCall:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
    }

    public double PerSession(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("PerSession:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
        return _result;
    }

    public double Singleton(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("Singleton:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
        return _result;
    }


    #endregion
}

//Host  httpBasicBinding
using (ServiceHost host = new ServiceHost(typeof(CalculatorService)))
{
    Console.Title = "WCF Service Host: Session";           
    host.Opened += delegate
    {
        Console.WriteLine("Calculator service has been host");
    }; 
    host.Open(); 
    Console.Read();
}

//Client  httpBasicBinding

Console.Title = "WCF Session: Client";

ChannelFactory<ICalculatorService> channelFactory = new ChannelFactory<ICalculatorService>("CalculatorServiceEndpoint");
ICalculatorService channel = channelFactory.CreateChannel();
try
{
    channel.PerCall(1, 1);
    Console.WriteLine("Channel PerCall 1");
    channel.PerCall(1, 1);
    Console.WriteLine("Channel PerCall 2");
}
catch (Exception ex)
{
    Console.WriteLine("Channel Exception:" + ex.Message);
}
(channel as ICommunicationObject).Close();
 
ICalculatorService channel2 = channelFactory.CreateChannel();
try
{
    channel2.PerCall(1, 1);
    Console.WriteLine("Channel2 PerCall 1");
    channel2.PerCall(1, 1);
    Console.WriteLine("Channel2 PerCall 2");
} 
catch (Exception ex)
{
    Console.WriteLine("Channel2 Exception:" + ex.Message);
}
(channel2 as ICommunicationObject).Close();
Console.Read();

 

//IService
[ServiceContract(SessionMode = SessionMode.Required)]
 public interface ICalculatorService
 {
     [OperationContract]
     void PerCall(double x, double y);
     [OperationContract]
     double PerSession(double x, double y);
     [OperationContract]
     double Singleton(double x, double y);

 }


//Service
public class CalculatorService : ICalculatorService
{
    #region Constructor
    public CalculatorService()
    {
        Console.WriteLine("Create Service Instance:Current session ID is: {0}", OperationContext.Current.SessionId);
    }
    #endregion

    #region Destructor 
    ~CalculatorService()
    {
        Console.WriteLine("Destory Service Instance:Current session ID is: {0}", OperationContext.Current.SessionId);
    }
    #endregion

    #region Result
    private double _result;
    public double Result
        {
            get
            {
                return _result;
            }
        }
    #endregion

    #region ICalculator Members

    public void PerCall(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("PerCall:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
    }

    public double PerSession(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("PerSession:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
        return _result;
    }

    public double Singleton(double x, double y)
    {            
        _result += x + y;
        Console.WriteLine("Singleton:Current session ID is: {0}", OperationContext.Current.SessionId);
        Console.WriteLine("Current result is {0}", _result.ToString());
        return _result;
    }

    #endregion
}


//Host
using (ServiceHost host = new ServiceHost(typeof(CalculatorService)))
{
    Console.Title = "WCF Service Host: Session";           
    host.Opened += delegate
    {
        Console.WriteLine("Calculator service has been host");
    }; 
    host.Open(); 
    Console.Read();
}

//Client
Console.Title = "WCF Session: Client";

ChannelFactory<ICalculatorService> channelFactory = new ChannelFactory<ICalculatorService>("CalculatorServiceEndpoint")
ICalculatorService channel = channelFactory.CreateChannel();
try
{
    double retValue = 0;
    retValue = channel.PerSession(1, 1);
    Console.WriteLine(string.Format("Channel PerCall 1,reback value is {0}",retValue.ToString()));
    retValue = channel.PerSession(1, 1);
    Console.WriteLine(string.Format("Channel PerCall 1,reback value is {0}", retValue.ToString()));
}
catch (Exception ex)
{
    Console.WriteLine("Channel Exception:" + ex.Message);
}
(channel as ICommunicationObject).Close();
 
ICalculatorService channel2 = channelFactory.CreateChannel();
try
{
    double retValue = 0;
    retValue = channel2.PerSession(1, 1);
    Console.WriteLine(string.Format("Channel PerCall 2,reback value is {0}", retValue.ToString()));
    retValue = channel2.PerSession(1, 1);
    Console.WriteLine(string.Format("Channel PerCall 2,reback value is {0}", retValue.ToString()));
} 
catch (Exception ex)
{
    Console.WriteLine("Channel2 Exception:" + ex.Message);
}
(channel2 as ICommunicationObject).Close();
Console.Read();