servlet实现浏览器文件下载

download.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <a href="/downloadServlet?filename=01.jpg">点击下载图片</a>
</body>
</html>

DownloadServlet.java

package com.zr.web.servlet;

import com.zr.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;

@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

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

        //解决中文名乱码问题
        //获取浏览器请求头
        String userAgent = resp.getHeader("user-agent");
        //使用DownLoadUtils工具类方法，处理编码格式
        filename = DownLoadUtils.getFileName(userAgent, filename);

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

        //4.将输入流的数据写出到输出流中
        ServletOutputStream sos = resp.getOutputStream();
        byte[] bytes=new byte[1024*8];
        int len;
        while ((len=fis.read(bytes))!=-1){
            sos.write(bytes,0,len);
        }
    }
}

DownLoadUtils.java
工具类

package com.zr.util;

import sun.misc.BASE64Encoder;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

/*
    改变文件名编码格式，避免中文乱码
 */
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
            filename = URLEncoder.encode(filename, "utf-8");
        }
        return filename;
    }
}

01.jpg

servlet实现浏览器文件下载

servlet实现浏览器文件下载

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