文件下载servlet端代码模版

private void downFile(File file,HttpServletResponse response) throws IOException {
// 写数据到客户端
response.setContentType("application/octet-stream");
response.setHeader("Cache-Control","must-revalidate, post-check=0, pre-check=0");
response.setHeader("Pragma", "public");
//设置超时时间
response.setDateHeader("Expires",(System.currentTimeMillis() + 5000));
response.addHeader("Content-Disposition","attachment; filename=\""+ file.getName() + "\"");
FileInputStream in = new FileInputStream(file);
OutputStream out = response.getOutputStream();
int len = 0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))!=-1){
out.write(buffer, 0, len);
out.flush();
}
out.close();
in.close();
}