HttpServletResponse下载文件

简称Response类

常见应用

1. 向浏览器输出消息
2. 下载文件
   1. 要获取下载文件的路径
   2. 下载文件的名称
   3. 设置想办法让浏览器能够支持下载我们需要的东西
   4. 获取下载文件的输入流
   5. 创建缓冲区
   6. 获取OutputStream对象
   7. 将FileOutputStream流写入到debuffer缓冲区
   8. 使用OutputStream将缓冲区的数据输出到客户端！

package com.yin;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

public class servlet1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //要获取下载文件的路径
        //String realPath=this.getServletContext().getRealPath("/1.png");
        String realPath="E:\\code\\maven0\\response1\\src\\main\\resources\\1.png";

        System.out.println("下载文件的路径:"+realPath);
        //下载文件的名称
        String filename=realPath.substring(realPath.lastIndexOf("\\")+1);
        //设置想办法让浏览器能够支持下载我们需要的东西
        //resp.setHeader("Content-Disposition", "attachment; filename="+ URLEncoder.encode(filename,"utf-8"));//可解决中文名乱码
        resp.setHeader("Content-Disposition", "attachment; filename="+filename);
        //获取下载文件的输入流
        FileInputStream in= new FileInputStream(realPath);
        //创建缓冲区
        int len=0;
        byte[] buffer=new byte[1024];
        //获取OutputStream对象
        ServletOutputStream out =resp.getOutputStream();

        //将FileOutputStream流写入到buffer缓冲区//使用OutputStream将缓冲区的数据输出到客户端！
        while( (len=in.read(buffer))>0)
            out.write(buffer,0,len);

        in.close();
        out.close();

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }
}