我们在管理网站文件时，可以把扩展名一样的文件放在同一个目录下­，起一个比较特别名字，例如放pdf文件目录为the_pdf_­file_s，把下面代码另存为down.asp，他的网上路径­为http://www.xx.com/down.asp，我们就可以用http://www.xx.com/down.asp?FileName=51windows.pdf来下载这个文件了，而且下载者无法看到这个文件实际下载路径的！在­down.asp中我们还可以设置下载文件是否需要登陆，判断下­载的来源页是否为外部网站，从而可以做到防止文件被盗链。
<%
From_url = Cstr(Request.ServerVariables("­HTTP_REFERER"))
Serv_url = Cstr(Request.ServerVariables("­SERVER_NAME"))
if mid(From_url,8,len(Serv_url)) <> Serv_url then
response.write "非法链接！" '防止盗链
response.end
end if

if Request.Cookies("Logined")="" then
response.redirect "/login.asp" '需要登陆！
end if
Function GetFileName(longname)'/folder1­/folder2/file.asp=>file.asp
while instr(longname,"/")
longname = right(longname,len(longname)-1­)
wend
GetFileName = longname
End Function
Dim Stream
Dim Contents
Dim FileName
Dim TrueFileName
Dim FileExt
Const adTypeBinary = 1
FileName = Request.QueryString("FileName"­)
if FileName = "" Then
Response.Write "无效文件名！"
Response.End
End if
FileExt = Mid(FileName, InStrRev(FileName, ".") + 1)
Select Case UCase(FileExt)
Case "ASP", "ASA", "ASPX", "ASAX", "MDB"
Response.Write "非法操作！"
Response.End
End Select
Response.Clear
if lcase(right(FileName,3))="gif" or lcase(right(FileName,3))="jpg" or
lcase(right(FileName,3))="png" then
Response.ContentType = "image/*"
'对图像文件不出现下载对话框
else
Response.ContentType = "application/ms-download"
end if
Response.AddHeader "content-disposition", "attachment; filename=" &
GetFileName(R equest.QueryStrin­g("FileName"))
Set Stream = server.CreateObject("ADODB.Str­eam")
Stream.Type = adTypeBinary
Stream.Open
if lcase(right(FileName,3))="pdf" then '设置pdf类型文件目录
TrueFileName = "/the_pdf_file_s/"&FileName
end if
if lcase(right(FileName,3))="doc" then '设置DOC类型文件目录
TrueFileName = "/my_D_O_C_file/"&FileName
end if
if lcase(right(FileName,3))="gif" or lcase(right(FileName,3))="jpg" or
lcase(right(FileName,3))="png" then
TrueFileName = "/all_images_/"&FileName '设置图像文件目录
end if
Stream.LoadFromFile Server.MapPath(TrueFileName)
While Not Stream.EOS
Response.BinaryWrite Stream.Read(1024 * 64)
Wend
Stream.Close
Set Stream = Nothing
Response.Flush
Response.End
%>

利用adodb.stream直接下载任何后缀的文件(防盗链)

在浏览器的地址栏里直接输入一个doc或xls或jpg的文件的­url路径，那么该文件会直接显示在浏览器里。而在很多时候我们­希望能直接弹出下载提示框让用户下载，我们该怎么办呢？这里有两­种方法：

1、设置你的服务器的iis，给doc等后缀名做映射
2、在向客户端发送时设置其contenttype

下面详细说明方法2
<%
Response.Buffer = true
Response.Clear

dim url
Dim fso,fl,flsize
dim Dname
Dim objStream,ContentType,flName,i­sre,url1
'*****************************­****************调用时传入的下载文件名

Dname=trim(request("n"))
'*****************************­******************************­*******
If Dname<>"" Then
'*****************************­*下载文件存放的服务端目录
url=server.MapPath("/")&"\"&Dn­ame
'*****************************­**********************
End If

Set fso=Server.CreateObject("Scrip­ting.FileSystemObject")
Set fl=fso.getfile(url)
flsize=fl.size
flName=fl.name
Set fl=Nothing
Set fso=Nothing
%>
<%
Set objStream = Server.CreateObject("ADODB.Str­eam")
objStream.Open
objStream.Type = 1
objStream.LoadFromFile url

Select Case lcase(Right(flName, 4))
Case ".asf"
ContentType = "video/x-ms-asf"
Case ".avi"
ContentType = "video/avi"
Case ".doc"
ContentType = "application/msword"
Case ".zip"
ContentType = "application/zip"
Case ".xls"
ContentType = "application/vnd.ms-excel"
Case ".gif"
ContentType = "image/gif"
Case ".jpg", "jpeg"
ContentType = "image/jpeg"
Case ".wav"
ContentType = "audio/wav"
Case ".mp3"
ContentType = "audio/mpeg3"
Case ".mpg", "mpeg"
ContentType = "video/mpeg"
Case ".rtf"
ContentType = "application/rtf"
Case ".htm", "html"
ContentType = "text/html"
Case ".txt"
ContentType = "text/plain"
Case Else
ContentType = "application/octet-stream"
End Select

Response.AddHeader "Content-Disposition", "attachment; filename=" &
flName
Response.AddHeader "Content-Length", flsize

Response.Charset = "UTF-8"
Response.ContentType = ContentType

Response.BinaryWrite objStream.Read
Response.Flush
response.Clear()
objStream.Close
Set objStream = Nothing

%>

将下面的东西存成download.asp然后你就可以用<a
herf="http://xxx.xxx.com/download.asp?n=file.doc">download!</a>来下载同一目录下的file.d­oc了!

但是这里有个问题就是直接将file.doc路径写在url里是­不安全的，所以解决方案应该是将file.doc的路径存到数据­库里，同过查找数据库后得到路径


在这个程序的最前面如果加上一个判断：

if
instr(Request.ServerVariables(­"HTTP_REFERER"),"http://你的域名")­=0
then
Response.End
end if