ASP.NET创建XML Web服务全接触(10)
发表时间:2024-02-07 来源:明辉站整理相关软件相关文章人气:
[摘要]和XML Web服务异步地通讯 和一个XML Web服务异步通讯遵循被Microsoft.NET Framework其它部分使用的异步设计模式。然而,在你取得那些细节之前,重要的是注意一个XML Web服务不必特意的写来处理用于异步调用的异步请求。你使用Wsdl.exe为你的客户端创建的代理类自...
和XML Web服务异步地通讯
和一个XML Web服务异步通讯遵循被Microsoft.NET Framework其它部分使用的异步设计模式。然而,在你取得那些细节之前,重要的是注意一个XML Web服务不必特意的写来处理用于异步调用的异步请求。你使用Wsdl.exe为你的客户端创建的代理类自动地创建用于异步调用XML Web服务方法的方法。即使只有一个XML Web服务方法的同步实现也是这样的。
.NET Framework异步方法调用设计模式
用于调用异步方法的设计模式,尤其是用于.NET Framework,针对每个同步方法分别有两个异步方法。对每个同步方法,都有一个Begin异步方法和一个End异步方法。Begin方法被客户端调用来开始方法调用。也就是说,客户端指示这个方法来开始处理方法调用,但是立即返回。End方法被客户端调用来取得XML Web服务方法调用执行的处理结果。
一个客户端如何知道何时调用End方法?.NET Framework定义了两种方法来实现客户端判断其时间。第一种是传送一个回调函数到Begin方法,当方法已经完成处理的时候调用。第二个方法是使用WaitHandle类的一个方法来导致客户端等待方法完成。当一个客户端实现第二个方法,并且调用Begin方法,返回值不是XML Web服务方法指定的数据类型,而是一个实现IAsyncResult接口的类型。IAsyncResult接口包含一个WaitHandle类型的AsyncWaitHandle属性,实现支持等待同步对象变为带有WaitHandle.WaitOne、WaitAny和WaitAll标记的方法。当一个同步对象被标记的时候,它指示等待特定的资源的线程可以访问资源的。如果一个XML Web服务客户端使用wait方法仅仅异步地调用一个XML Web服务方法,那么它可以调用WaitOne来等待XML Web服务方法完成处理。
重要的是注意不管客户端选择来与XML Web服务异步通讯的两种方法中的哪一种,SOAP消息发送和接收都与同步通信时吻合。也就是说,只有一个SOAP请求和SOAP响应通过网络发送和接收。代理类通过使用一个不同的线程而不是客户端用来调用Begin方法的线程来处理SOAP响应。因此,客户端可以继续执行线程上的其它的工作,而代理类处理接收和操作SOAP响应。
实现一个产生异步的方法调用的XML Web服务客户端
用于从使用ASP.NET创建的XML Web服务客户端产生一个到XML Web服务的异步调用的体系结构被嵌入.NET Framework和由Wsdl.exe构造的代理类中。用于异步调用的设计模式被.NET Framework定义,代理类提供和一个XML Web服务异步通信的机制。当一个用于XML Web服务的代理类被使用Wsdl.exe构造的时候,有三个方法分别被创建,用于XML Web服务中的公共XML Web服务方法。下面的表格描述那三个方法。
代理类中的方法名 描述
<NameOfWebServiceMethod> 同步发送用于名为<NameOfWebServiceMethod>的XML Web服务方法的消息。
Begin<NameOfWebServiceMethod> 开始与名为<NameOfWebServiceMethod>的XML Web服务方法的异步消息通信。
End<NameOfWebServiceMethod> 结束与名为<NameOfWebServiceMethod>的XML Web服务方法的异步消息通信,从XML Web服务方法中取得完成的消息。
下面的代码示例是一个XML Web服务方法,它可能花费相对长的时间来完成处理。因此,当你应该设置你的XML Web服务客户端来异步地调用XML Web服务方法的时候,它是一个很好的示例。
[C#] <%@ WebService Language="C#" Class="PrimeFactorizer" %>
using System; using System.Collections; using System.Web.Services;
class PrimeFactorizer {
[WebMethod] public long[] Factorize(long factorizableNum){ ArrayList outList = new ArrayList(); long i = 0; int j; try{ long Check = factorizableNum;
//Go through every possible integer //factor between 2 and factorizableNum / 2. //Thus, for 21, check between 2 and 10. for (i = 2; i < (factorizableNum / 2); i++){ while(Check % i == 0){ outList.Add(i); Check = (Check/i); } } //Double-check to see how many prime factors have been added. //If none, add 1 and the number. j = outList.Count; if (j == 0) { outList.Add(1); outList.Add(factorizableNum); } j = outList.Count;
//Return the results and //create an array to hold them. long[] primeFactor = new long[j]; for (j = 0; j < outList.Count; j++){ //Pass the values one by one, making sure //to convert them to type ulong. primeFactor[j] = Convert.ToInt64(outList[j]); } return primeFactor; } catch (Exception) { return null; } } }
[Visual Basic] <%@ WebService Class="PrimeFactorizer" Language="VB" %> Imports System Imports System.Collections Imports System.Web.Services
Public Class PrimeFactorizer <WebMethod> _ Public Function Factorize(factorizableNum As Long) As Long() Dim outList As New ArrayList() Dim i As Long = 0 Dim j As Integer Try Dim Check As Long = factorizableNum
'Go through every possible integer 'factor between 2 and factorizableNum / 2. 'Thus, for 21, check between 2 and 10. For i = 2 To CLng(factorizableNum / 2) - 1 While Check Mod i = 0 outList.Add(i) Check = CLng(Check / i) End While Next i 'Double-check to see how many prime factors have been added. 'If none, add 1 and the number. j = outList.Count If j = 0 Then outList.Add(1) outList.Add(factorizableNum) End If j = outList.Count
'Return the results and 'create an array to hold them. Dim primeFactor(j - 1) As Long For j = 0 To outList.Count - 1 'Pass the values one by one, making sure 'to convert them to type ulong. primeFactor(j) = CLng(outList(j)) Next j Return primeFactor Catch Return Nothing End Try End Function End Class |
下面的代码示例是一个Wsdl.exe生成的代理类的一部分,用于上述XML Web服务方法。注意BeginFactorize和EndFactorize方法,因为它们被用来与Factorize XML Web服务方法异步通信。
public class PrimeFactorizer : System.Web.Services.Protocols.SoapHttpClientProtocol {
public long[] Factorize(long factorizableNum) { object[] results = this.Invoke("Factorize", new object[] { factorizableNum}); return ((long[])(results[0])); }
public System.IAsyncResult BeginFactorize(long factorizableNum, System.AsyncCallback callback, object asyncState) { return this.BeginInvoke("Factorize", new object[] { factorizableNum}, callback, asyncState); }
public long[] EndFactorize(System.IAsyncResult asyncResult) { object[] results = this.EndInvoke(asyncResult); return ((long[])(results[0])); } } |
有两个方法用来和XML Web服务方法异步通信。下面的代码示例说明了如何与一个XML Web服务方法异步通信,并且使用回调函数来取得XML Web服务方法的结果。
[C#] using System; using System.Runtime.Remoting.Messaging; using MyFactorize;
class TestCallback { public static void Main(){ long factorizableNum = 12345; PrimeFactorizer pf = new PrimeFactorizer();
//Instantiate an AsyncCallback delegate to use as a parameter //in the BeginFactorize method. AsyncCallback cb = new AsyncCallback(TestCallback.FactorizeCallback);
// Begin the Async call to Factorize, passing in our // AsyncCalback delegate and a reference // to our instance of PrimeFactorizer. IAsyncResult ar = pf.BeginFactorize(factorizableNum, cb, pf);
// Keep track of the time it takes to complete the async call // as the call proceeds. int start = DateTime.Now.Second; int currentSecond = start; while (ar.IsCompleted == false){ if (currentSecond < DateTime.Now.Second) { currentSecond = DateTime.Now.Second; Console.WriteLine("Seconds Elapsed..." + (currentSecond - start).ToString() ); } } // Once the call has completed, you need a method to ensure the // thread executing this Main function // doesn't complete prior to the call-back function completing. Console.Write("Press Enter to quit"); int quitchar = Console.Read(); } // Set up a call-back function that is invoked by the proxy class // when the asynchronous operation completes. public static void FactorizeCallback(IAsyncResult ar) { // You passed in our instance of PrimeFactorizer in the third // parameter to BeginFactorize, which is accessible in the // AsyncState property. PrimeFactorizer pf = (PrimeFactorizer) ar.AsyncState; long[] results;
// Get the completed results. results = pf.EndFactorize(ar);
//Output the results. Console.Write("12345 factors into: "); int j; for (j = 0; j<results.Length;j++){ if (j == results.Length - 1) Console.WriteLine(results[j]); else Console.Write(results[j] + ", "); } } }
[Visual Basic] Imports System Imports System.Runtime.Remoting.Messaging Imports MyFactorize
Public Class TestCallback Public Shared Sub Main() Dim factorizableNum As Long = 12345 Dim pf As PrimeFactorizer = new PrimeFactorizer()
'Instantiate an AsyncCallback delegate to use as a parameter ' in the BeginFactorize method. Dim cb as AsyncCallback cb = new AsyncCallback(AddressOf TestCallback.FactorizeCallback)
' Begin the Async call to Factorize, passing in the ' AsyncCallback delegate and a reference to our instance ' of PrimeFactorizer. Dim ar As IAsyncResult = pf.BeginFactorize(factorizableNum, cb, pf)
' Keep track of the time it takes to complete the async call as ' the call proceeds. Dim start As Integer = DateTime.Now.Second Dim currentSecond As Integer = start Do while (ar.IsCompleted = false) If (currentSecond < DateTime.Now.Second) Then currentSecond = DateTime.Now.Second Console.WriteLine("Seconds Elapsed..." + (currentSecond - start).ToString() ) End If Loop
' Once the call has completed, you need a method to ensure the ' thread executing this Main function ' doesn't complete prior to the callback function completing. Console.Write("Press Enter to quit") Dim quitchar As Integer = Console.Read() End Sub
' Set up the call-back function that is invoked by the proxy ' class when the asynchronous operation completes. Public Shared Sub FactorizeCallback(ar As IAsyncResult)
' You passed in the instance of PrimeFactorizer in the third ' parameter to BeginFactorize, which is accessible in the ' AsyncState property.
Dim pf As PrimeFactorizer = ar.AsyncState Dim results() as Long
' Get the completed results. results = pf.EndFactorize(ar)
'Output the results. Console.Write("12345 factors into: ") Dim j as Integer For j = 0 To results.Length - 1 If j = (results.Length - 1) Then Console.WriteLine(results(j) ) Else Console.Write(results(j).ToString + ", ") End If Next j End Sub End Class |
下面的代码示例说明了如何与一个XML Web服务方法异步通信,然后使用一个同步对象来等待处理结束。
[C#] // -----------------------------------------------------------------------// Async Variation 2. // Asynchronously invoke the Factorize method, //without specifying a call back. using System; using System.Runtime.Remoting.Messaging; // MyFactorize, is the name of the namespace in which the proxy class is // a member of for this sample. using MyFactorize;
class TestCallback { public static void Main(){ long factorizableNum = 12345; PrimeFactorizer pf = new PrimeFactorizer();
// Begin the Async call to Factorize. IAsyncResult ar = pf.BeginFactorize(factorizableNum, null, null);
// Wait for the asynchronous operation to complete. ar.AsyncWaitHandle.WaitOne();
// Get the completed results. long[] results; results = pf.EndFactorize(ar);
//Output the results. Console.Write("12345 factors into: "); int j; for (j = 0; j<results.Length;j++){ if (j == results.Length - 1) Console.WriteLine(results[j]); else Console.Write(results[j] + ", "); } } }
[Visual Basic] Imports System Imports System.Runtime.Remoting.Messaging Imports MyFactorize ' Proxy class namespace
Public Class TestCallback Public Shared Sub Main() Dim factorizableNum As Long = 12345 Dim pf As PrimeFactorizer = new PrimeFactorizer()
' Begin the Async call to Factorize. Dim ar As IAsyncResult = pf.BeginFactorize(factorizableNum, Nothing, Nothing)
' Wait for the asynchronous operation to complete. ar.AsyncWaitHandle.WaitOne()
' Get the completed results. Dim results() as Long results = pf.EndFactorize(ar)
'Output the results. Console.Write("12345 factors into: ") Dim j as Integer For j = 0 To results.Length - 1 If j = (results.Length - 1) Then Console.WriteLine(results(j) ) Else Console.Write(results(j).ToString + ", ") End If Next j End Sub End Class |
注意:如果FactorizeCallback是一个需要同步化/线成亲和上下文的上下文绑定类,那么回调被通过上下文分配体系结构来分配。换句话说,相对于它的对这样的上下文的调用者,回调可能异步的执行。在方法标记上有单向修饰词的精确的语义。这指的是任何这样的方法调用可能同步地或异步地执行,相对于调用者,并且在执行控制返回给它的时候,调用者不能产生任何关于完成这样一个调用的假设。
而且,在异步操作完成之前调用EndInvoke将阻塞调用者。使用相同的AsyncResult再次调用它的行为是不确定的。
Cancel方法是一个在过去一段特定时间之后取消方法处理的请求。注意它是一个客户端的请求,并且最好服务器对此有所承诺。在接收到方法已经被取消的消息之后,客户端就不必做服务器是否已经停止处理的假设了。客户端最好不要破坏资源,例如文件对象,因为服务器可能仍然需要使用它们。IAsyncResult实例的IsCompleted属性在服务器结束它的处理之后将被设置为true,不再使用任何客户端提供的资源。因此,IsCompleted属性设置为true之后,客户端就可以安全的销毁资源了。