在 .NET 中使用 WEB SERVICE 的CallBacks机制 (4)

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测试

WEB SERVICE Callbacks的概念和设计能使用下列位于http://localhost虚拟目录的三个子项目一起测试。测试的概要已经在上述段落中（Web Service Callback部分）说明。所有项目已经加入了跟踪断点，这样我们可以清楚的看到程序运行的过程(http://www.sysinternals.com/)。下面是它们的实现代码：

1. Web Service A

namespace WebServiceA

{

public class ServiceA : System.Web.Services.WebService

{

public ServiceA()

{

//CODEGEN: This call is required by the ASP.NET Web Services Designer

InitializeComponent();

Trace.WriteLine(string.Format("[{0}]ServiceA.ctor", GetHashCode()));

}

#region Component Designer generated code

private void InitializeComponent()

{

}

#endregion

protected override void Dispose( bool disposing )

{

Trace.WriteLine(string.Format("[{0}]ServiceA.Dispose", GetHashCode()));

}

[WebMethod]

public string DoSomeWorkA(int count, string ticket)

{

Trace.WriteLine(string.Format("[{0}]ServiceA.DoSomeWorkA start...",

GetHashCode()));

int startTC = Environment.TickCount;

// current state

Global.state[ticket] = "The job has been started";

string state = ticket;

// location of the source/target web services -

// (hard coded for test purpose only!)

string myWsdlUrl = "http://localhost/WebServiceA/ServiceA.asmx?wsdl";

string targetWsdlUrl = "http://localhost/WebServiceB/ServiceB.asmx?wsdl";

// call the WebService B

WebServiceAccessor wsa = new WebServiceAccessor(targetWsdlUrl);

object esObj = wsa.CreateInstance("ServiceB");

object retval = wsa.Invoke(esObj, "BeginDoSomeWorkB", count,

myWsdlUrl, state, null, null);

// Wait for the call to complete

WebClientAsyncResult ar = retval as WebClientAsyncResult;

ar.AsyncWaitHandle.WaitOne();

// retrieve a result

object result = wsa.Invoke(esObj, "EndDoSomeWorkB", ar);

int durationTC = Environment.TickCount - startTC;

Trace.WriteLine(string.Format("[{0}]ServiceA.DoSomeWorkA done in {1}ms",

GetHashCode(), durationTC));

Global.state.Remove(ticket);

return result.ToString();

}

[WebMethod]

public bool CallbackServiceA(string sender, string xmlEventArg)

{

WebServiceEventArgs ea = (WebServiceEventArgs)xmlEventArg;

string msg = string.Format(

"[{0}]ServiceA.CallbackServiceA({1}, [{2},{3},{4}])",

GetHashCode(), sender, ea.name, ea.state, ea.param);

if(Global.state.ContainsKey(ea.state))

{

Global.state[ea.state] = string.Format("{0}, [{1},{2},{3}]",

sender, ea.name, ea.state, ea.param);

Trace.WriteLine(msg);

return true;

}

return false;

}

[WebMethod]

public string AbortWorkA(string ticket)

{

Trace.WriteLine(string.Format("[{0}]ServiceA.AbortWorkA",

GetHashCode()));

if(Global.state.ContainsKey(ticket))

{

Global.state.Remove(ticket);

return string.Format("#{0} aborted.", ticket);

}

return string.Format("#{0} doesn't exist.", ticket);

}

[WebMethod]

public string GetStatusWorkA(string ticket)

{

if(Global.state.ContainsKey(ticket))

{

return string.Format("#{0} status: {1}", ticket, Global.state[ticket]);

}

return string.Format("#{0} doesn't exist.", ticket);

}

全局类:

namespace WebServiceA

{

public class Global : System.Web.HttpApplication

{

static public Hashtable state = null;

protected void Application_Start(Object sender, EventArgs e)

{

state = Hashtable.Synchronized(new Hashtable());

Trace.WriteLine(string.Format("[{0}]ServiceA.Application_Start",

GetHashCode()));

}

// ...

protected void Application_End(Object sender, EventArgs e)

{

state.Clear();

Trace.WriteLine(string.Format("[{0}]ServiceA.Application_End",

GetHashCode()));

}

请求和Callback Web Methods运行在不同的Session 中，这是状态为什么保存在可共享的资源类(如Hashtable)中的原因。每个客户端的请求有一个单独的票据凭证，它是WEB SERVICE和全球站点之间的一把通信钥匙（cookie)。

2. Web Service B

这个网络服务非常简单。只有一个 Web Methods模拟一些工作。程序运行期间，服务开始启用Callback Web Methods。工作以同步的方式在运行一些循环操作。每个循环调用WebService”A”的Callback Web Methods，基于它的返回值，程序可以自动停止。Service. 可以在session中保持状态。

namespace WebServiceB

{

public class ServiceB : System.Web.Services.WebService

{

public ServiceB()

{

//CODEGEN: This call is required by the ASP.NET Web Services Designer

InitializeComponent();

Trace.WriteLine(string.Format("[{0}]ServiceB.ctor", GetHashCode()));

}

#region Component Designer generated code

private void InitializeComponent()

{

}

#endregion

protected override void Dispose( bool disposing )

{

Trace.WriteLine(string.Format("[{0}]ServiceB.Dispose", GetHashCode()));

}

[WebMethod(EnableSession=true)]

public string DoSomeWorkB(int count, string callbackWS, string stateWS)

{

Trace.WriteLine(string.Format("[{0}]ServiceB.DoSomeWorkB start...",

GetHashCode()));

int startTC = Environment.TickCount;

// async call to the ServiceA.CallbackServiceA method

WebServiceAccessor wsa = new WebServiceAccessor(callbackWS);

object esObj = wsa.CreateInstance("ServiceA");

// prepare the callback arguments: sender, EventArgs

string sender = GetType().FullName;

WebServiceEventArgs ea = new WebServiceEventArgs();

ea.name = "This is a callback";

ea.state = stateWS;

for(int ii = 0; ii < (count & 0xff); ii++) // max. count = 255

{

ea.param = ii;

string xmlEventArgs = ea;

object retval = wsa.Invoke(esObj, "BeginCallbackServiceA",

sender, xmlEventArgs, null, null);

// simulate some task

Thread.Sleep(250);

// Wait for the call to complete

WebClientAsyncResult ar = retval as WebClientAsyncResult;

ar.AsyncWaitHandle.WaitOne();

// result

object result = wsa.Invoke(esObj, "EndCallbackServiceA", ar);

if((bool)result == false)

{

Trace.WriteLine(string.Format(

"[{0}]ServiceB.DoSomeWorkB has been aborted", GetHashCode()));

return string.Format("#{0} aborted during the progress of {1}.",

stateWS, ii);

}

int durationTC = Environment.TickCount - startTC;

Trace.WriteLine(string.Format("[{0}]ServiceB.DoSomeWorkB done in {1}ms",

GetHashCode(), durationTC));

return string.Format("#{0} done in {1}ms", stateWS, durationTC);

}