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
'
' 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://jb51.net", 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
'
' 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。
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