ASP/VBScript动态创建属性对象的工厂类(DynamicObject)
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最近整理ASP/VBScript代码，发现过去的一个ASP实现的MVC框架，可惜是个半成品，效率也成问题，不过发现里面有些我写的代码，感觉还稍稍可以拿出来见人，于是今天作此文以记之。
说是ASP，其实和VBScript也脱不了干系，VBScript语言传承于Visual Basic，VB的语法灵活度已经不尽如人意了，VBS作为其子集可想而知。神马反射、自省等先进的技术，微软在.NET中才引入。作为被抛弃的技术，也不奢望微软能够提供支持，于是顽固守旧的程序员只有绞尽脑汁的去模仿实现一些类似的功能。
好吧，我承认很长一段时间我就是顽固守旧派中的一员，今天介绍的就是其中的一项功能，动态创建一个属性对象，属性对象姑且这么称呼，也就是说动态创建的对象只包含属性(Properties)。
下面贴出实现代码供大家参考：
'
' ASP/VBScript Dynamic Object Generator
' Author: WangYe
' For more information please visit
' http://wangye.org/
' This code is distributed under the BSD license
'
Const PROPERTY_ACCESS_READONLY = 1
Const PROPERTY_ACCESS_WRITEONLY = -1
Const PROPERTY_ACCESS_ALL = 0
Class DynamicObject
Private m_objProperties
Private m_strName
Private Sub Class_Initialize()
Set m_objProperties = CreateObject("Scripting.Dictionary")
m_strName = "AnonymousObject"
End Sub
Private Sub Class_Terminate()
If Not IsObject(m_objProperties) Then
m_objProperties.RemoveAll
End If
Set m_objProperties = Nothing
End Sub
Public Sub setClassName(strName)
m_strName = strName
End Sub
Public Sub add(key, value, access)
m_objProperties.Add key, Array(value, access)
End Sub
Public Sub setValue(key, value, access)
If m_objProperties.Exists(key) Then
m_objProperties.Item(key)(0) = value
m_objProperties.Item(key)(1) = access
Else
add key,value,access
End If
End Sub
Private Function getReadOnlyCode(strKey)
Dim strPrivateName, strPublicGetName
strPrivateName = "m_var" & strKey
strPublicGetName = "get" & strKey
getReadOnlyCode = _
"Public Function " & strPublicGetName & "() :" & _
strPublicGetName & "=" & strPrivateName & " : " & _
"End Function : Public Property Get " & strKey & _
" : " & strKey & "=" & strPrivateName & " : End Property : "
End Function
Private Function getWriteOnlyCode(strKey)
Dim pstr
Dim strPrivateName, strPublicSetName, strParamName
strPrivateName = "m_var" & strKey
strPublicSetName = "set" & strKey
strParamName = "param" & strKey
getWriteOnlyCode = _
"Public Sub " & strPublicSetName & "(" & strParamName & ") :" & _
strPrivateName & "=" & strParamName & " : " & _
"End Sub : Public Property Let " & strKey & "(" & strParamName & ")" & _
" : " & strPrivateName & "=" & strParamName & " : End Property : "
End Function
Private Function parse()
Dim i, Keys, Items
Keys = m_objProperties.Keys
Items = m_objProperties.Items
Dim init, pstr
init = ""
pstr = ""
parse = "Class " & m_strName & " :" & _
"Private Sub Class_Initialize() : "
Dim strPrivateName
For i = 0 To m_objProperties.Count - 1
strPrivateName = "m_var" & Keys(i)
init = init & strPrivateName & "=""" & _
Replace(CStr(Items(i)(0)), """", """""") & """:"
pstr = pstr & "Private " & strPrivateName & " : "
If CInt(Items(i)(1)) > 0 Then ' ReadOnly
pstr = pstr & getReadOnlyCode(Keys(i))
ElseIf CInt(Items(i)(1)) < 0 Then ' WriteOnly
pstr = pstr & getWriteOnlyCode(Keys(i))
Else ' AccessAll
pstr = pstr & getReadOnlyCode(Keys(i)) & _
getWriteOnlyCode(Keys(i))
End If
Next
parse = parse & init & "End Sub : " & pstr & "End Class"
End Function
Public Function getObject()
Call Execute(parse)
Set getObject = Eval("New " & m_strName)
End Function
Public Sub invokeObject(ByRef obj)
Call Execute(parse)
Set obj = Eval("New " & m_strName)
End Sub
End Class
对于属性对象分别提供了Property直接访问模式和set或者get函数访问模式，当然我还提供了三种权限控制，在add方法中使用，分别是
PROPERTY_ACCESS_READONLY
（属性只读）、
PROPERTY_ACCESS_WRITEONLY
（属性只写）和
PROPERTY_ACCESS_ALL
（属性读写），你可以像下面这样使用（一个例子）：
Dim DynObj
Set DynObj = New DynamicObject
DynObj.add "Name", "WangYe", PROPERTY_ACCESS_READONLY
DynObj.add "HomePage", "http://wangye.org", PROPERTY_ACCESS_READONLY
DynObj.add "Job", "Programmer", PROPERTY_ACCESS_ALL
'
' 如果没有setClassName，
' 新创建的对象将会自动命名为AnonymousObject
' 但是如果创建多个对象，就必须指定名称
' 否则就可能引起对象名重复的异常
DynObj.setClassName "User"
Dim User
Set User = DynObj.GetObject()
' 或者 DynObj.invokeObject User
Response.Write User.Name
' Response.Write User.getName()
Response.Write User.HomePage
' Response.Write User.getHomePage()
Response.Write User.Job
' Response.Write User.getJob()
' 改变属性值
User.Job = "Engineer"
' User.setJob "Engineer"
Response.Write User.getJob()
Set User = Nothing
Set DynObj = Nothing其原理很简单，就是通过给定的Key-Value动态生成VBS Class脚本代码，然后调用Execute执行以便于将这段代码加入到代码上下文流中，最后再通过Eval新建这个对象。
好了，就介绍到这里，今后我可能还会陆续公开一些Classic ASP的相关技巧代码。
2012年11月7日更新
修复从旧项目移植过来导致的BUG。
修复了一些Bug增加了一些特性，我先把最新的代码贴出来供大家参考：
'
' ASP/VBScript Dynamic Object Generator
' Author: WangYe
' For more information please visit
' http://wangye.org/
' This code is distributed under the BSD license
'
' UPDATE:
' 2012/11/7
' 1. Add variable key validator.
' 2. Add hasattr_ property for determine
' if the property exists.
' 3. Add getattr_ property for get property
' value safety.
' 4. Class name can be accessed by ClassName_ property.
' 5. Fixed some issues.
'
Const PROPERTY_ACCESS_READONLY = 1
Const PROPERTY_ACCESS_WRITEONLY = -1
Const PROPERTY_ACCESS_ALL = 0
Class DynamicObject
Private m_objProperties
Private m_strName
Private m_objRegExp
Private Sub Class_Initialize()
Set m_objProperties = CreateObject("Scripting.Dictionary")
Set m_objRegExp = New RegExp
m_objRegExp.IgnoreCase = True
m_objRegExp.Global = False
m_objRegExp.Pattern = "^[a-z][a-z0-9]*$"
m_strName = "AnonymousObject"
m_objProperties.Add "ClassName_", _
Array(m_strName, PROPERTY_ACCESS_READONLY)
End Sub
Private Sub Class_Terminate()
Set m_objRegExp = Nothing
If IsObject(m_objProperties) Then
m_objProperties.RemoveAll
End If
Set m_objProperties = Nothing
End Sub
Public Sub setClassName(strName)
If Not m_objRegExp.Test(strName) Then
' Skipped Invalid Class Name
' Raise
Exit Sub
End If
m_strName = strName
m_objProperties("ClassName_") = _
Array(m_strName, PROPERTY_ACCESS_READONLY)
End Sub
Public Sub add(key, value, access)
If Not m_objRegExp.Test(key) Then
' Skipped Invalid key
' Raise
Exit Sub
End If
If key = "hasattr_" Then key = "hasattr__"
If key = "ClassName_" Then key = "ClassName__"
'Response.Write key
m_objProperties.Add key, Array(value, access)
End Sub
Public Sub setValue(key, value, access)
If m_objProperties.Exists(key) Then
m_objProperties.Item(key)(0) = value
m_objProperties.Item(key)(1) = access
Else
add key,value,access
End If
End Sub
Private Function getReadOnlyCode(strKey)
Dim strPrivateName, strPublicGetName
strPrivateName = "m_var" & strKey
strPublicGetName = "get" & strKey
getReadOnlyCode = _
"Public Function " & strPublicGetName & "() :" & _
strPublicGetName & "=" & strPrivateName & " : " & _
"End Function : Public Property Get " & strKey & _
" : " & strKey & "=" & strPrivateName & _
" : End Property : "
End Function
Private Function getWriteOnlyCode(strKey)
Dim pstr
Dim strPrivateName, strPublicSetName, strParamName
strPrivateName = "m_var" & strKey
strPublicSetName = "set" & strKey
strParamName = "param" & strKey
getWriteOnlyCode = _
"Public Sub " & strPublicSetName & _
"(" & strParamName & ") :" & _
strPrivateName & "=" & strParamName & " : " & _
"End Sub : Public Property Let " & strKey & _
"(" & strParamName & ")" & _
" : " & strPrivateName & "=" & strParamName & _
" : End Property : "
End Function
Private Function parse()
Dim i, Keys, Items
Keys = m_objProperties.Keys
Items = m_objProperties.Items
Dim init, pstr
init = ""
pstr = ""
parse = "Class " & m_strName & " :" & _
"Private Sub Class_Initialize() : "
Dim strPrivateName, strAvailableKeys
For i = 0 To m_objProperties.Count - 1
strPrivateName = "m_var" & Keys(i)
init = init & strPrivateName & "=""" & _
Replace(CStr(Items(i)(0)), """", """""") & """:"
pstr = pstr & "Private " & strPrivateName & " : "
strAvailableKeys = strAvailableKeys & Keys(i) & ","
If CInt(Items(i)(1)) > 0 Then ' ReadOnly
pstr = pstr & getReadOnlyCode(Keys(i))
ElseIf CInt(Items(i)(1)) < 0 Then ' WriteOnly
pstr = pstr & getWriteOnlyCode(Keys(i))
Else ' AccessAll
pstr = pstr & getReadOnlyCode(Keys(i)) & _
getWriteOnlyCode(Keys(i))
End If
Next
init = init & "m_strAvailableKeys = Replace(""," & _
strAvailableKeys & """, "" "", """") : "
Dim hasstmt
hasstmt = "Private m_strAvailableKeys : " & _
"Public Function hasattr_(ByVal key) : " & _
"hasattr_ = CBool(InStr(m_strAvailableKeys," & _
" "","" & key & "","") > 0) : " & _
"End Function : " & _
"Public Function getattr_(ByVal key, ByVal defaultValue) : " & _
"If hasattr_(key) Then : getattr_ = Eval(key) : " & _
"Else : getattr_ = defaultValue : End If : " & _
"End Function : "
parse = parse & init & "End Sub : " & _
hasstmt & pstr & "End Class"
End Function
Public Function getObject()
'Response.Write parse
Call Execute(parse)
Set getObject = Eval("New " & m_strName)
End Function
Public Sub invokeObject(ByRef obj)
Call Execute(parse)
Set obj = Eval("New " & m_strName)
End Sub
End Class需要注意的几个新特性：
1. 增加了类名和属性名验证措施，防止畸形的类名或者属性名导致动态生成的代码出现语法错误。不过处理的方式是直接忽略，本来想Raise异常的，但考虑到VBS对异常处理不是很好的，所以采取忽略策略：
' 有效的类名或属性名必须以字母开头
Dim DynObj
Set DynObj = New DynamicObject
DynObj.setClassName "1User" ' 此句将被忽略，因为类名不能以数字开始
' 下面这句也会被忽略，因为属性名不能以特殊符号开始
DynObj.add "%Name", "WangYe", PROPERTY_ACCESS_READONLY
Set DynObj = Nothing
2. 对于动态对象增加了
hasattr_
方法，该属性用于检测此对象是否支持相应的属性，可以在访问一个属性前先确定该对象是否支持此属性：
Dim DynObj
Set DynObj = New DynamicObject
DynObj.add "Name", "WangYe", PROPERTY_ACCESS_READONLY
Response.Write DynObj.hasattr_("Name") ' True
Response.Write DynObj.hasattr_("Favor") ' False
Set DynObj = Nothing
3. 对于动态对象增加了
getattr_
方法，此方法可以安全的获取指定的属性值，避免因为对象不存在属性值导致出错。方法原型为
getattr_(ByVal propertyName, ByVal defaultValue)
，参数
propertyName
指定属性的名字，
defaultValue
是当指定属性不存在是可以返回的默认值，比如下面代码：
Dim DynObj
Set DynObj = New DynamicObject
DynObj.add "Name", "WangYe", PROPERTY_ACCESS_READONLY
Response.Write DynObj.getattr_("Name", "N/A") ' WangYe
Response.Write DynObj.getattr_("Favor", "N/A") ' N/A
Set DynObj = Nothing
4. 动态对象的类名可以通过
ClassName_
属性或者
getClassName_()
方法获取。
2012年11月12日更新
修复双引号导致构造类错误或导致执行任意代码的Bug。