用stream直接下载文件

  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

就能够很好的防止别人的盗链了