Responseオブジェクトを使用したファイルのダウンロード

package com.lijiaming.servlet;

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;

/**
 * @基本功能:
 * @ClassName: FileServlet
 * @Description: TODO
 * @Author: lijiaming
 * @Date: 2022/2/17 21:45
 * @Version 1.0
 */
public class FileServlet extends HttpServlet {
    
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
    
        //1、要获取下载文件的路径 C:\Users\李嘉明\Desktop\Java学习\JavaWeb\Maven_parent\Servlet01\src\main\resources\1.jpg
        String realPath = "C:\\Users\\李嘉明\\Desktop\\Java学习\\JavaWeb\\Maven_parent\\Servlet01\\src\\main\\resources\\1.jpg";
        System.out.println("下载文件的路径："+ realPath);
        //2、下载的文件名是啥
        String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
        System.out.println("文件名字为："+fileName);
        //3、设置想办法让浏览器能够支持(Content-Disposition)下载我们需要的东西,中文文件 名URLEncoder.encode编码，否则有可能乱码
        resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"UTF-8"));
        //4、获取下载文件的输入流
        FileInputStream in = new FileInputStream(realPath);
        //5、创建缓冲区
        int len = 0;
        byte[] buffer = new byte[1024];
        //6、获取OutputStream对象
        ServletOutputStream outputStream = resp.getOutputStream();
        // 7. 将FileOutputStream流写入到buffer缓冲区,使用OutputStream将缓冲区中的数据 输出到客户端！
        while((len=in.read(buffer))>0){
    
    
            outputStream.write(buffer,0,len);
        }
        in.close();
        outputStream.close();
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
    
        doGet(req,resp);
    }
}