JavaWeb----文件的下载

1.问题说明：

实现文件下载，且下载的文件名不会出现乱码现象（主流浏览器:Google、IE、火狐、360）

2.页面预览

代码布局

3.代码实现

3.1 index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>下载文件资源</title>
</head>
<body>
<h1>文件资源的下载</h1>
    <a href="./img/2.jpg">图片预览</a>
    <hr>
    <a href="./downloadServlet?filename=长春工业大学校徽.jpg">图片下载链接</a> &nbsp;|&nbsp;
    <a href="./downloadServlet?filename=长春工业大学宣传片.avi">视频下载链接</a>
</body>
</html>

3.2 downLinkServlet.java

package com.ccut.servlet;

import com.ccut.util.DownLoadUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;

/**
 * @ClssName:downLinkServlet
 * @Author:Mr.Tony
 * @Description:
 * @Create: 2020-05-12 16:18
 * @Version: v1.0
 */

@WebServlet("/downloadServlet")
public class downLinkServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取请求参数，文件名称
        String filename = request.getParameter("filename");
        //2.使用字节输入流加载文件进内存
        //2.1找到文件服务器路径
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("/img/" + filename);
        //2.2用字节流关联
        FileInputStream fis = new FileInputStream(realPath);

        //3.设置response的响应头
        //3.1设置响应头类型：content-type
        String mimeType = servletContext.getMimeType(filename);//获取文件的mime类型
        response.setHeader("content-type", mimeType);
        //3.2设置响应头打开方式:content-disposition

        //解决中文文件名问题
        //1.获取user-agent请求头、
        String agent = request.getHeader("user-agent");
        //2.使用工具类方法编码文件名即可
        filename = DownLoadUtils.getFileName(agent, filename);
        response.setHeader("content-disposition", "attachment;filename=" + filename);
        //4.将输入流的数据写出到输出流中
        ServletOutputStream sos = response.getOutputStream();
        byte[] buff = new byte[1024 * 8];
        int len = 0;
        while ((len = fis.read(buff)) != -1) {
            sos.write(buff, 0, len);
        }
        fis.close();
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

3.3-1 DownLoadUtils.java(我用jdk 11，jdk9以上含jdk9)

package com.ccut.util;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.Base64;
import java.util.Base64.Encoder;
public class DownLoadUtils {
    public static String getFileName(String agent, String filename) throws UnsupportedEncodingException {
        if (agent.contains("MSIE")) {
            // IE浏览器
            filename = URLEncoder.encode(filename, "utf-8");
            filename = filename.replace("+", " ");
        } else if (agent.contains("Firefox")) {
            // 火狐浏览器
         Encoder encoder = Base64.getEncoder();
        filename = "=?utf-8?B?" + encoder.encodeToString(filename.getBytes("utf-8")) + "?=";
        } else {
            // 其它浏览器
            //filename = URLEncoder.encode(filename, "utf-8");
            //苹果Safari浏览器也支持
            filename = new String(filename.getBytes("UTF-8"), "ISO-8859-1");
}
        return filename;
    }
}

3.3-2 DownLoadUtils.java(jdk 8以下包含jdk8)

package com.ccut.util;
import sun.misc.BASE64Encoder;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
public class DownLoadUtils {
    public static String getFileName(String agent, String filename) throws UnsupportedEncodingException {
        if (agent.contains("MSIE")) {
            // IE浏览器
            filename = URLEncoder.encode(filename, "utf-8");
            filename = filename.replace("+", " ");
        } else if (agent.contains("Firefox")) {
            // 火狐浏览器
            BASE64Encoder base64Encoder = new BASE64Encoder();
            filename = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
        } else {
            // 其它浏览器 苹果浏览器不支持
            //filename = URLEncoder.encode(filename, "utf-8");
           //苹果Safari浏览器也支持
            filename = new String(filename.getBytes("UTF-8"), "ISO-8859-1");
            
        }
        return filename;
    }
}

说明:
原因是/lib/tool.jar和/lib/rt.jar已经从Java SE 9中删除

测试火狐浏览器

测试Google浏览器

MD5的加密现方法(jdk9.0 含9.0)
import java.util.Base64.Encoder
import java.util.Base64.Decoder

Encoder encoder = Base64.getEncoder();
String result = encoder.encodeToString(byteArray);

Decoder decoder = Base64.getDecoder();
byte[] result = decoder.decode(str);

原方法(jdk8.0 含8.0)
BASE64Encoder encoder = new BASE64Encoder();
String imagestr = encoder.encode(captcha);
BASE64Decoder decoder = new BASE64Decoder();
byte[] bytes = decoder.decodeBuffer(imagestr);

posted @ 2020-05-12 17:21 Tony小哥阅读(229) 评论(1) 编辑收藏举报

刷新页面返回顶部

Tony小哥