問題：
存在一個1G多的XML文件，需要將其中的數據，按照一定的邏輯提取數據，做一定的格式化處理和處理邏輯，生成3個不同的文本文件
解決：
做XML的轉換，有如下的幾個選擇：1. DOM + XSL ；2. DOM + 自己解析 ； 3：SAX + 自己解析。因為擔心performance的問題，所以決定采用SAX + Stack的方式來處理。因為要生成3個文件，所以設計3個類來負責分別產生3個文件。然后通過鏈表的方式串接起來，讓他們截獲自己concern的內容，做進一步的處理。最后各自產生自己負責的文件。
其中：
XmlTextReader : VB.NET的SAX XML Reader。他會逐一讀到XML的指令，COMMENT，開始TAG，文本，結束TAG等內容
Processor : 解析XML，產生文本文件的處理器接口。里面定義了5個方法。他們分別是，open()：用來打開文件；close()：用來關閉文件；startTag()：當XmlTextReader讀到開始TAG的時候，就會呼叫Processor的這個方法，將TAG名字，Tag的Stack，Value的Stack作為參數傳入；endTag()：當XmlTextReader讀到結束TAG的時候，就會呼叫Processor的這個方法，將TAG名字，Tag的Stack，Value的Stack作為參數傳入；text()：當XmlTextReader讀到文本內容的時候，就會呼叫Processor的這個方法，將文本值，Tag的Stack，Value的Stack作為參數傳入
Executor：作為XmlTextReader和各種Processor交互的橋梁。在他的內部，各種不同的Processor會以鏈表的形式組合在一塊兒。當XmlTextReader讀到開始Tag，文本，結束Tag的時候，就會去invoke Excutor的相應方法，而Executor則會逐一invoke 各種processor相應方法，若其中有一procceor處理了某個請求，則終止向后續傳。最后一個DefaultProcessor，他的存在只是為了保證tagStask，valueStack的完整性而已。
TProcessor，DProcessor，PProcessor：負責接收只有自己感興趣的xml內容，然后轉交給TagWrapper，做格式化，業務邏輯處理而已。在startTag()，text()方法里面，處理邏輯是，如果是自己關心的內容，則直接入棧；在endTag()方法里面，處理邏輯是，如果是自己關心的內容，則判斷是否到了一條記錄生成完成的時候（根據endTag標志），如果是則將記錄寫入到文件當中，否則將startTag出棧，valueTag出棧，將value，tag名字交給TagWrapper鏈表，做內部的格式化和業務邏輯處理。
程序的流程如下：
部分程序代碼（VB.NET）
Main的部分
Dim m_xmlr As XmlTextReader
Dim tagStack As New Stack
Dim valueStack As New Stack
Dim executor As Processor = New Executor("c:\TOTFA", "c:\DTLFA", "c:\ORDFA")
executor.open()
m_xmlr = New XmlTextReader("c:\test2.xml")
m_xmlr.WhitespaceHandling = WhitespaceHandling.None
While m_xmlr.Read()
Select Case m_xmlr.NodeType
Case XmlNodeType.XmlDeclaration
Continue While
Case XmlNodeType.ProcessingInstruction
Continue While
Case XmlNodeType.Element
executor.startTag(m_xmlr.Name, tagStack, valueStack)
Case XmlNodeType.EndElement
executor.endTag(m_xmlr.Name, tagStack, valueStack)
Case XmlNodeType.Text
executor.text(m_xmlr.Value, tagStack, valueStack)
End Select
End While
m_xmlr.Close()
executor.close()Executor的部分
Public Class Executor
Implements Processor
Private list As New List(Of Processor)
Public Sub New(ByVal TOTFA As String, ByVal DTLFA As String, ByVal ORDFA As String)
Dim tp As TProcessor = New TProcessor(TOTFA)
Dim dp As DProcessor = New DProcessor(DTLFA, tp)
Dim pp As PProcessor = New PProcessor(ORDFA, tp, dp)
list.Add(tp)
list.Add(dp)
list.Add(pp)
list.Add(New DefaultProcessor())
End Sub
Function startTag(ByVal tagName As String, ByRef tagStack As Stack, ByRef valueStack As Stack) As Boolean Implements Processor.startTag
Dim index As Integer = list.Count
For index = 0 To list.Count - 1
Dim processor As Processor = list.Item(index)
If (processor.startTag(tagName, tagStack, valueStack)) Then
Return True
End If
Next
Return True
End Function
Function endTag(ByVal tagName As String, ByRef tagStack As Stack, ByRef valueStack As Stack) As Boolean Implements Processor.endTag
Dim index As Integer = list.Count
For index = 0 To list.Count - 1
Dim processor As Processor = list.Item(index)
If (processor.endTag(tagName, tagStack, valueStack)) Then
Return True
End If
Next
Return True
End Function
Function text(ByVal value As String, ByRef tagStack As Stack, ByRef valueStack As Stack) As Boolean Implements Processor.text
Dim index As Integer = list.Count
For index = 0 To list.Count - 1
Dim processor As Processor = list.Item(index)
If (processor.text(value, tagStack, valueStack)) Then
Return True
End If
Next
Return True
End Function
Sub open() Implements Processor.open
Dim index As Integer = list.Count
For index = 0 To list.Count - 1
Dim processor As Processor = list.Item(index)
processor.open()
Next
End Sub
Sub close() Implements Processor.close
Dim index As Integer = list.Count
For index = 0 To list.Count - 1
Dim processor As Processor = list.Item(index)
processor.close()
Next
End Sub
End Class
TProcessor代碼
Imports System.IO
Imports System.Text
Imports System.Text.RegularExpressions
Public Class TProcessor
Implements Processor
Private tagWrapperList As New List(Of TagWrapper)
Private sw As StreamWriter
Private filename As String
Public Sub New(ByVal filename As String)
Me.filename = filename
tagWrapperList.Add(New TagWrapper("t1", "欄位說明", " ", 2, 0, FormatterFactory.getInstance().getRBlankFormatter()))
tagWrapperList.Add(New TagWrapper("t2", "欄位說明", " ", 10, 0, FormatterFactory.getInstance().getRBlankFormatter()))
tagWrapperList.Add(New TagWrapper("t3", "欄位說明", "00000", 5, 0, FormatterFactory.getInstance().getYearMonthFormatter()))
tagWrapperList.Add(New TagWrapper("t4", "欄位說明", " ", 1, 0, FormatterFactory.getInstance().getRBlankFormatter()))
tagWrapperList.Add(New TagWrapper("t5", "欄位說明", " ", 1, 0, FormatterFactory.getInstance().getRBlankFormatter()))
tagWrapperList.Add(New TagWrapper("t6", "欄位說明", "0000000", 7, 0, FormatterFactory.getInstance().getYearMonthDateFormatter()))
tagWrapperList.Add(New TagWrapper("t7", "欄位說明", "000000", 6, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t8", "欄位說明", "0000000000", 10, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t9", "欄位說明", "000000", 6, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t10", "欄位說明", "0000000000", 10, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t11", "欄位說明", "000000", 6, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t12", "欄位說明", "0000000000", 10, 0, FormatterFactory.getInstance().getRZeroFormatter()))
tagWrapperList.Add(New TagWrapper("t13", "欄位說明", "000000", 6, 0, FormatterFactory.getInstance().getRZeroFormatter()))
End Sub
Public Sub close() Implements Processor.close
If Not (sw Is Nothing) Then
sw.Close()
End If
End Sub
Public Function endTag(ByVal tagName As String, ByRef tagStack As System.Collections.Stack, ByRef valueStack As System.Collections.Stack) As Boolean Implements Processor.endTag
‘匹配TProcessor所關心的代碼
If (Not Regex.IsMatch(tagName, "tdata|t\d+") Or String.Compare(tagName, tagStack.Peek) <> 0) Then
Return False
End If
If (String.Compare(tagStack.Peek, "tdata") = 0 And String.Compare(tagName, tagStack.Peek) = 0) Then
tagStack.Pop()
flush()
ElseIf (valueStack.Count <> 0 And String.Compare(tagStack.Peek, tagName) = 0) Then
execute(tagStack.Pop(), valueStack.Pop())
End If
Return True
End Function
Public Sub open() Implements Processor.open
sw = New StreamWriter(Me.filename)
End Sub
Public Function startTag(ByVal tagName As String, ByRef tagStack As System.Collections.Stack, ByRef valueStack As System.Collections.Stack) As Boolean Implements Processor.startTag
If (Not Regex.IsMatch(tagName, "tdata|t\d+")) Then
Return False
End If
tagStack.Push(tagName)
Return True
End Function
Public Function text(ByVal value As String, ByRef tagStack As System.Collections.Stack, ByRef valueStack As System.Collections.Stack) As Boolean Implements Processor.text
If (Not Regex.IsMatch(tagStack.Peek, "tdata|t\d+")) Then
Return False
End If
valueStack.Push(value)
Return True
End Function
Private Sub flush()
Dim ret As StringBuilder = New StringBuilder("")
Dim index As Integer
For index = 0 To tagWrapperList.Count - 1
Dim tag As TagWrapper = tagWrapperList.Item(index)
ret.Append(tag.getFormatValue())
Next
sw.Write(ret.ToString)
sw.Flush()
End Sub
Private Sub execute(ByVal tagName As String, ByVal value As String)
For index = 0 To tagWrapperList.Count - 1
Dim wrapper As TagWrapper = tagWrapperList.Item(index)
If (wrapper.accept(tagName)) Then
wrapper.Value = value
Exit Sub
End If
Next
End Sub
End Class