Servlet下载文件

package com.itcast.web.controller;

import com.itcast.utils.DownLoadUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class DownLoadServlet extends HttpServlet {

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

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //获取文件名
        String fileName = req.getParameter("fileName");

        //获取文件真实路径
        ServletContext servletContext = req.getServletContext();
        String realPath = servletContext.getRealPath("/download/" + fileName);

        //获取文件类型
        String mimeType = servletContext.getMimeType(fileName);//根据文件名后缀去tomcat的web.xml中获取文件类型image/jpeg
        resp.setHeader("Content-type", mimeType);

        // 设置 下载附加 attachment 表示附件 , filename就是下载后的文件名称
        long l = System.currentTimeMillis();
        //解决中文文件名乱码问题
        String encodeFileName = DownLoadUtils.encodeFileName(req, fileName);
        resp.setHeader("Content-Disposition", "attachment;filename=" + encodeFileName + "_" + l);

        //文件读写
        FileInputStream bis = new FileInputStream(realPath);
        BufferedOutputStream bos = new BufferedOutputStream(resp.getOutputStream());

        //循环读写
        byte[] b = new byte[1024];
        int len;
        while ((len = bis.read(b)) != -1) {
            bos.write(b, 0, len);
        }

        bos.close();
        bis.close();

    }
}

package utils;

import sun.misc.BASE64Encoder;

import javax.servlet.http.HttpServletRequest;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

public class DownLoadUtils {

    public static String encodeFileName(HttpServletRequest request, String fileName) {
        String name = "";

        String agent = request.getHeader("User-Agent");
        System.out.println(agent);
        try {
            if (agent.contains("Firefox")) {
                BASE64Encoder base64Encoder = new BASE64Encoder();
                name = "=?UTF-8?B?" + new String(base64Encoder.encode(fileName.getBytes("UTF-8"))) + "?=";
            } else {
                name = URLEncoder.encode(fileName, "UTF-8");
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        //System.out.println(name);
        return name;
    }
}

本文地址：https://blog.csdn.net/weixin_42210904/article/details/109588866