将SAX加入我们的ASP应用中

  在处理大型的XML文档的时候，在服务器端直接使用XML DOM的时候速度是比较慢的，当我第一次接触到SAX的时候，我意识到我们应该在服务器端将DOM和SAX结合起来以提高我们程序的效率。我们在ASP中最常使用的就是使用COM来完成这个工作（也许你有更好的方法）。
废话少说，还是直接进入实际的代码部分了（下面只是包含了最基本的代码而已）。

首先我们创建一个DLL来封装SAX的功能好了。
测试环境：Win2k Prof.+MSXML3.0 sp1+VB6
要使用SAX我们必须引用（Reference）Microsoft XML 3.0（我的机器安装的是MSXML3.0 sp1）

工程名：SAXTesting

类名：clsSAXTest
方法：Public Function MyXMLParser(XML文件物理路径) as DOMDocument
代码：
Option Explicit

Public Function MyXMLParser(ByVal strXMLFilePath As Variant) As DOMDocument
Dim reader As New SAXXMLReader
Dim contentHandler As New ContentHandlerImpl
Dim errorHandler As New ErrorHandlerImpl

Set reader.contentHandler = contentHandler
Set reader.errorHandler = errorHandler
On Error GoTo ErrorHandle
Dim XMLFile As String
XMLFile = strXMLFilePath
reader.parseURL (XMLFile)

Dim xmlDoc As MSXML2.DOMDocument
Set xmlDoc = CreateObject("MSXML2.DOMDocument")
xmlDoc.loadXML strXML
Set MyXMLParser = xmlDoc
Set xmlDoc = Nothing
Exit Function

ErrorHandle:
Err.Raise 9999, "My XML Parser", Err.Number & " : " & Err.Description

End Function

类名:modPublic
代码：
Option Explicit

Global strXML As String

类名：ContentHandlerImpl
代码：
Option Explicit

Implements IVBSAXContentHandler

Private Sub IVBSAXContentHandler_startElement(strNamespaceURI As String, strLocalName As String,

strQName As String, ByVal attributes As MSXML2.IVBSAXAttributes)

Dim i As Integer

intLocker = intLocker + 1
If intLocker > 1 Then

End If
strXML = strXML & "<" & strLocalName

For i = 0 To (attributes.length - 1)
strXML = strXML & " " & attributes.getLocalName(i) & "=""" & attributes.getValue(i) &

""""
Next

strXML = strXML & ">"

If strLocalName = "qu" Then
Err.Raise vbObjectError + 1, "ContentHandler.startElement", "Found element <qu>"
End If

End Sub

Private Sub IVBSAXContentHandler_endElement(strNamespaceURI As String, strLocalName As String,

strQName As String)

strXML = strXML & "</" & strLocalName & ">"

End Sub

Private Sub IVBSAXContentHandler_characters(text As String)
text = Replace(text, vbLf, vbCrLf)
strXML = strXML & text

End Sub

Private Property Set IVBSAXContentHandler_documentLocator(ByVal RHS As MSXML2.IVBSAXLocator)

End Property

Private Sub IVBSAXContentHandler_endDocument()

End Sub

Private Sub IVBSAXContentHandler_endPrefixMapping(strPrefix As String)

End Sub

Private Sub IVBSAXContentHandler_ignorableWhitespace(strChars As String)

End Sub

Private Sub IVBSAXContentHandler_processingInstruction(target As String, data As String)

strXML = strXML & "<?" & target & " " & data & ">"

End Sub

Private Sub IVBSAXContentHandler_skippedEntity(strName As String)

End Sub

Private Sub IVBSAXContentHandler_startDocument()

End Sub

Private Sub IVBSAXContentHandler_startPrefixMapping(strPrefix As String, strURI As String)

End Sub

类名：ErrorHandlerImpl
代码：
Option Explicit

Implements IVBSAXErrorHandler

Private Sub IVBSAXErrorHandler_fatalError(ByVal lctr As IVBSAXLocator, msg As String, ByVal

errCode As Long)

strXML = strXML & "*** error *** " & msg

End Sub

Private Sub IVBSAXErrorHandler_error(ByVal lctr As IVBSAXLocator, msg As String, ByVal errCode As

Long)

End Sub

Private Sub IVBSAXErrorHandler_ignorableWarning(ByVal oLocator As MSXML2.IVBSAXLocator,

strErrorMessage As String, ByVal nErrorCode As Long)

End Sub

OK，让我们编译这个DLL，应该是没什么问题了。让我们在ASP中看看运行的结果怎么样：
XML文件：
<?xml version="1.0"?>
<root foo="bar.com">
<PARTS>
<PART foo="bar.com" foo2="bar.com">
<PARTNO>12345</PARTNO>
<DESCRIPTION>VIP - Very Important Part</DESCRIPTION>
</PART>
<PART>
<PARTNO>5678</PARTNO>
<DESCRIPTION>LIP - Less Important Part</DESCRIPTION>
</PART>
</PARTS>
</root>

ASP文件：
<%
Set a = CreateObject("SAXTesting.clsSAXTest")
Set xmlDoc = a.MyXMLParser("D:\test.xml")
Response.contenttype="text/xml"
response.write xmlDoc.xml
set xmlDoc=nothing
set a=nothing
%>