用jsp方式通知客户端下载文件

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@page import="java.io.FileInputStream"%><%@page import="java.io.OutputStream"%><%
    String realpath = application.getRealPath("/images/1.jpg");
    FileInputStream in = new FileInputStream(realpath);
    //通知客户端以下载方式
    response.setHeader("Content-Disposition","attachment;filename=1.jpg");
    OutputStream os = response.getOutputStream();
    byte buf[] = new byte[1024];
    int len = -1;
    while((len=in.read(buf))!=-1){
    	os.write(buf,0,len);
    }
    in.close();
     %>