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前面我們已經介紹了使用ASP和XML混合編程，那是因為ASP頁面能夠很容易讓我們看清應用程序正在做什么，但是你如果你不想使用ASP的話，你也可以使用任何你熟悉的技術去創建一個客戶端程序。下面，我提供了一段VB代碼，它的功能和ASP頁面一樣，也可以顯示相同的數據，但是這個VB程序不會創建發送到服務器的XML字符串。它通過運行一個名叫Initialize的存儲過程，從服務器取回XML字符串，來查詢ClientCommands表的內容。
ClientCommands表包括兩個域：command_name域和command_xml域。客戶端程序需要三個特定的command_name域:getCustomerList,CustOrderHist和RecentPurchaseByCustomerID。每一個命令的command_xml域包括程序發送到getData.asp頁面的XML字符串，這樣，就可以集中控制XML字符串了，就象存儲過程名字所表現的意思一樣，在發送XML字符串到getData.asp之前，客戶端程序使用XML DOM來設置存儲過程的參數值。我提供的代碼，包含了用于定義Initialize過程和用于創建ClientCommands表的SQL語句。
我提供的例程中還說明了如何使用XHTTPRequest對象實現我在本文一開始時許下的承諾:任何遠程的機器上的應用程序都可以訪問getData.asp；當然，你也可以通過設置IIS和NTFS權限來限制訪問ASP頁面；你可以在服務器上而不是客戶機上存儲全局應用程序設置；你可以避免通過網絡發送數據庫用戶名和密碼所帶來的隱患性。還有，在IE中，應用程序可以只顯示需要的數據而不用刷新整個頁面。
在實際的編程過程中，你們應當使用一些方法使應用程序更加有高效性。你可以把ASP中的關于取得數據的代碼端搬到一個COM應用程序中去然后創建一個XSLT變換來顯示返回的數據。好，我不多說了，現在你所要做的就是試一試吧！
Option Explicit
Private RCommands As Recordset
Private RCustomers As Recordset
Private RCust As Recordset
Private sCustListCommand As String
Private Const dataURL = "http://localhost/XHTTPRequest/getData.asp"
Private arrCustomerIDs() As String
Private Enum ActionEnum
VIEW_HISTORY = 0
VIEW_RECENT_PRODUCT = 1
End Enum
Private Sub dgCustomers_Click()
Dim CustomerID As String
CustomerID = RCustomers("CustomerID").Value
If CustomerID ＜＞ "" Then
If optAction(VIEW_HISTORY).Value Then
Call getCustomerDetail(CustomerID)
Else
Call getRecentProduct(CustomerID)
End If
End If
End Sub
Private Sub Form_Load()
Call initialize
Call getCustomerList
End Sub
Sub initialize()
' 從數據庫返回命令名和相應的值
Dim sXML As String
Dim vRet As Variant
Dim F As Field
sXML = "＜?xml version=""1.0""?＞"
sXML = sXML & "＜command＞＜commandtext＞Initialize＜/commandtext＞"
sXML = sXML & "＜returnsdata＞True＜/returnsdata＞"
sXML = sXML & "＜/command＞"
Set RCommands = getRecordset(sXML)
Do While Not RCommands.EOF
For Each F In RCommands.Fields
Debug.Print F.Name & "=" & F.Value
Next
RCommands.MoveNext
Loop
End Sub
Function getCommandXML(command_name As String) As String
RCommands.MoveFirst
RCommands.Find "command_name='" & command_name & "'", , adSearchForward, 1
If RCommands.EOF Then
MsgBox "Cannot find any command associated with the name '" & command_name & "'."
Exit Function
Else
getCommandXML = RCommands("command_xml")
End If
End Function
Sub getRecentProduct(CustomerID As String)
Dim sXML As String
Dim xml As DOMDocument
Dim N As IXMLDOMNode
Dim productName As String
sXML = getCommandXML("RecentPurchaseByCustomerID")
Set xml = New DOMDocument
xml.loadXML sXML
Set N = xml.selectSingleNode("command/param[name='CustomerID']/value")
N.Text = CustomerID
Set xml = executeSPWithReturn(xml.xml)
productName = xml.selectSingleNode("values/ProductName").Text
' 顯示text域
txtResult.Text = ""
Me.txtResult.Visible = True
dgResult.Visible = False
' 顯示product名
txtResult.Text = "最近的產品是: " & productName
End Sub
Sub getCustomerList()
Dim sXML As String
Dim i As Integer
Dim s As String
sXML = getCommandXML("getCustomerList")
Set RCustomers = getRecordset(sXML)
Set dgCustomers.DataSource = RCustomers
End Sub
Sub getCustomerDetail(CustomerID As String)
' 找出列表中相關聯的ID號
Dim sXML As String
Dim R As Recordset
Dim F As Field
Dim s As String
Dim N As IXMLDOMNode
Dim xml As DOMDocument
sXML = getCommandXML("CustOrderHist")
Set xml = New DOMDocument
xml.loadXML sXML
Set N = xml.selectSingleNode("command/param[name='CustomerID']/value")
N.Text = CustomerID
Set R = getRecordset(xml.xml)
' 隱藏 text , 因為它是一個記錄集
txtResult.Visible = False
dgResult.Visible = True
Set dgResult.DataSource = R
End Sub
Function getRecordset(sXML As String) As Recordset
Dim R As Recordset
Dim xml As DOMDocument
Set xml = getData(sXML)
Debug.Print TypeName(xml)
On Error Resume Next
Set R = New Recordset
R.Open xml
If Err.Number ＜＞ 0 Then
MsgBox Err.Description
Exit Function
Else
Set getRecordset = R
End If
End Function
Function executeSPWithReturn(sXML As String) As DOMDocument
Dim d As New Dictionary
Dim xml As DOMDocument
Dim nodes As IXMLDOMNodeList
Dim N As IXMLDOMNode
Set xml = getData(sXML)
If xml.documentElement.nodeName = "values" Then
Set executeSPWithReturn = xml
Else
'發生錯誤
Set N = xml.selectSingleNode("response/data")
If Not N Is Nothing Then
MsgBox N.Text
Exit Function
Else
MsgBox xml.xml
Exit Function
End If
End If
End Function
Function getData(sXML As String) As DOMDocument
Dim xhttp As New XMLHTTP30
xhttp.Open "POST", dataURL, False
xhttp.send sXML
Debug.Print xhttp.responseText
Set getData = xhttp.responseXML
End Function
Private Sub optAction_Click(Index As Integer)
Call dgCustomers_Click
End Sub
代碼二、getData.asp
＜%@ Language=VBScript %＞
＜% option explicit %＞
＜%
Sub responseError(sDescription)
Response.Write "＜response＞＜data＞Error: " & sDescription & "＜/data＞＜/response＞"
Response.end
End Sub
Response.ContentType="text/xml"
dim xml
dim commandText
dim returnsData
dim returnsValues
dim recordsAffected
dim param
dim paramName
dim paramType
dim paramDirection
dim paramSize
dim paramValue
dim N
dim nodeName
dim nodes
dim conn
dim sXML
dim R
dim cm
' 創建DOMDocument對象
Set xml = Server.CreateObject("msxml2.DOMDocument")
xml.async = False
' 裝載POST數據
xml.Load Request
If xml.parseError.errorCode ＜＞ 0 Then
Call responseError("不能裝載 XML信息。 描述: " & xml.parseError.reason & "＜br＞行數: " & xml.parseError.Line)
End If
' 客戶端必須發送一個commandText元素
Set N = xml.selectSingleNode("command/commandtext")
If N Is Nothing Then
Call responseError("Missing ＜commandText＞ parameter.")
Else
commandText = N.Text
End If
' 客戶端必須發送一個returnsdata或者returnsvalue元素
set N = xml.selectSingleNode("command/returnsdata")
if N is nothing then
set N = xml.selectSingleNode("command/returnsvalues")
if N is nothing then
call responseError("Missing ＜returnsdata＞ or ＜returnsValues＞ parameter.")
else
returnsValues = (lcase(N.Text)="true")
end if
else
returnsData=(lcase(N.Text)="true")
end if
set cm = server.CreateObject("ADODB.Command")
cm.CommandText = commandText
if instr(1, commandText, " ", vbBinaryCompare) ＞ 0 then
cm.CommandType=adCmdText
else
cm.CommandType = adCmdStoredProc
end if
' 創建參數
set nodes = xml.selectNodes("command/param")
if nodes is nothing then
' 如果沒有參數
elseif nodes.length = 0 then
' 如果沒有參數
else
for each param in nodes
' Response.Write server.HTMLEncode(param.xml) & "＜br＞"
on error resume next
paramName = param.selectSingleNode("name").text
if err.number ＜＞ 0 then
call responseError("創建參數: 不能發現名稱標簽。")
end if
paramType = param.selectSingleNode("type").text
paramDirection = param.selectSingleNode("direction").text
paramSize = param.selectSingleNode("size").text
paramValue = param.selectSingleNode("value").text
if err.number ＜＞ 0 then
call responseError("參數名為 '" & paramName & "'的參數缺少必要的域")
end if
cm.Parameters.Append cm.CreateParameter(paramName,paramType,paramDirection,paramSize,paramValue)
if err.number ＜＞ 0 then
call responseError("不能創建或添加名為 '" & paramName & "的參數.' " & err.description)
Response.end
end if
next
on error goto 0
end if
'打開連結
set conn = Server.CreateObject("ADODB.Connection")
conn.Mode=adModeReadWrite
conn.open Application("ConnectionString")
if err.number ＜＞ 0 then
call responseError("連結出錯: " & Err.Description)
Response.end
end if
' 連結Command對象
set cm.ActiveConnection = conn
' 執行命令
if returnsData then
' 用命令打開一個Recordset
set R = server.CreateObject("ADODB.Recordset")
R.CursorLocation = adUseClient
R.Open cm,,adOpenStatic,adLockReadOnly
else
cm.Execute recordsAffected, ,adExecuteNoRecords
end if
if err.number ＜＞ 0 then
call responseError("執行命令錯誤 '" & Commandtext & "': " & Err.Description)
Response.end
end if
if returnsData then
R.Save Response, adPersistXML
if err.number ＜＞ 0 then
call responseError("數據集發生存儲錯誤，在命令'" & CommandText & "': " & Err.Description)
Response.end
end if
elseif returnsValues then
sXML = "＜?xml version=""1.0"" encoding=""gb2312""?＞" & vbcrlf & "＜values＞"
set nodes = xml.selectNodes("command/param[direction='2']")
for each N in nodes
nodeName = N.selectSingleNode("name").text
sXML = sXML & "＜" & nodename & "＞" & cm.Parameters(nodename).Value & "" & "＜/" & nodename & "＞"
next
sXML = sXML & "＜/values＞"
Response.Write sXML
end if
set cm = nothing
conn.Close
set R = nothing
set conn = nothing
Response.end
%＞
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