VB 使用 XMLHttp Pool 的例子

概述代码： Form：Form1 Option Explicit Private Pools As HttpPool Private Sub Command1_Click()     Dim o As MSXML2.XMLHTTP     Set o = Pools.GetObject()     Dim Handler  As MyReadyStateHandler     Set Handler

代码：

Form：Form1

Option Explicit

Private Pools As httpPool

Private Sub Command1_Click()
Dim o As MSXML2.XMLhttp
Set o = Pools.Getobject()
Dim Handler As MyReadyStateHandler
Set Handler = New MyReadyStateHandler
Handler.ini o
o.OnReadyStateChange = Handler
o.open "GET","Http://localhost/js/message.htm",True
o.send
Set Handler = nothing
End Sub

Private Sub Form_Load()
Set Pools = New httpPool
End Sub

Private Sub Form_Unload(Cancel As Integer)
Set Pools = nothing
End Sub

Class：httpPool

Option Explicit

Dim Pool As Collection

'没有考虑池容量
Public Function Getobject() As MSXML2.XMLhttp
Dim i As Integer
Dim o As MSXML2.XMLhttp
For i = 1 To Pool.Count
Set o = Pool(i)
If o.readyState = 4 Or o.readyState = 0 Then
o.abort
GoTo ExitLabel
End If
Next
Set o = New MSXML2.XMLhttp
Pool.Add o
ExitLabel:
Set Getobject = o
DeBUG.Print Pool.Count
End Function

Private Sub Class_Initialize()
Set Pool = New Collection
End Sub

Private Sub Class_Terminate()
Dim i As Integer
For i = 1 To Pool.Count
Pool(i).abort
Next
Set Pool = nothing
End Sub

Option Explicit

Dim p As XMLhttp

Sub OnReadyStateChange()
If p.readyState = 4 Then
DeBUG.Print p.responseText
End If
End Sub

Class：MyReadyStateHandler

Public Sub ini(o As XMLhttp) Set p = oEnd Sub在原先的JavaScript的代码中没有黄色代码对应的语句，因此在VB6的调试过程中一点一个XMlhttp对象被用过后readyState状态一直是4，所以就不在触发OnReadyStateChange事件了，因此responseText只能显示一次，以后就无法工作了，最后加上o.abort一切搞定。

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