response.setContentType("APPLICATION/OCTET-STREAM"); 
 
response.setHeader("Content-Disposition","attachment; filename=\"" +  filename + "\""); 

String filename = urlFile.substring(urlFile.lastIndexOf("/")+1); //得到文件名
// 打开指定文件的流信息      
java.io.FileInputStream fileInputStream = new java.io.FileInputStream(realFile); //realFile为文件绝对路径
         
// 写出流信息 
 int i; 
 while ((i=fileInputStream.read()) != -1) 
 { 
    response.write(i); 
 } 
 fileInputStream.close();