使用Adodb.Stream下载大文件的问题

DATE: 2016-11-10 / VIEWS: 1310

使用Adodb.Stream下载文件，如下代码
程序代码 程序代码
Response.ContentType = "application/octet-stream"
response.AddHeader "Content-Disposition","attachment;filename=" & objRs("Attach_Name")& filetype
Set Stream = Server.CreateObject("ADODB.Stream")
Stream.type=1
Stream.Open
Stream.LoadFromFile server.mappath(objRs("Attach_path"))
Response.BinaryWrite Stream.Read
Stream.Close
Set Stream = Nothing

当下载文件小于4M时没问题，大于4M时出错，提示 ：

Response对象错误 'ASP 0251 : 80004005'    
    
超过响应缓冲区限制

问题出在IIS的配制中AspBufferingLimit只有4M，所以有如下几种解决办法：

1、修改IIS的配制

停止IIS服务，然后用记事本修改C:\WINDOWS\system32\inetsrv\MetaBase.xml 中的:  
   AspBufferingLimit="4194304"    //即默认4M  
  改为:  
   AspBufferingLimit="8388608"    //改为8M或更多，自己决定

2、如果不想修改IIS的默认配制就要修改代码了。
程序代码 程序代码
Response.Buffer=False ‘将Response.Buffer设为否
Response.ContentType = "application/octet-stream"
response.AddHeader "Content-Disposition","attachment;filename=" & objRs("Attach_Name")& filetype
Set Stream = Server.CreateObject("ADODB.Stream")
Stream.type=1
Stream.Open
Stream.LoadFromFile server.mappath(objRs("Attach_path"))
offset = 0
ChunkSize = 2048*1024 ‘ChunkSize小于IIS配制文件中的AspBufferingLimit项所设置的大小
TotalSize = Stream.Size
while offset < TotalSize
if (TotalSize - offset < ChunkSize) then
ChunkSize = TotalSize – offset
end if
strChunk = Stream.Read(ChunkSize)
Response.BinaryWrite strChunk
offset = offset + ChunkSize
wend
Stream.Close

或者
程序代码 程序代码
Response.Buffer= true ‘使用缓冲区
Response.Clear
Response.ContentType = "application/octet-stream"
response.AddHeader "Content-Disposition","attachment;filename=" & objRs("Attach_Name")& filetype
Set Stream = Server.CreateObject("ADODB.Stream")
Stream.type=1
Stream.Open
Stream.LoadFromFile server.mappath(objRs("Attach_path"))
offset = 0
ChunkSize = 2048*1024
TotalSize = Stream.Size
while offset < TotalSize
if (TotalSize - offset < ChunkSize) then
ChunkSize = TotalSize – offset
end if
strChunk = Stream.Read(ChunkSize)
Response.BinaryWrite strChunk
response.flush ‘这句很重要，它把缓冲区的数据据推出去
offset = offset + ChunkSize
wend
Stream.Close