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Servlet的文件下载案例

程序员文章站 2022-06-02 13:54:37
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案例需求分析与步骤

Servlet的文件下载案例

下载页面的代码实现

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <a href="/08_response/downloadServlet?filename=素描1.jpg">素描风景</a>
    <a href="/08_response/downloadServlet?filename=夏天的风.mp3">夏天的风</a>
</body>
</html>

文件下载的Servlet代码部分

package pers.cb.web.download;

import pers.cb.web.utils.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 {
    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();
        //判断文件类型来找到文件服务器路径
        String realPath = null;
        if (filename.endsWith(".jpg"))
        {
            realPath = servletContext.getRealPath("/img/" + filename);
        }
        if (filename.endsWith(".mp3"))
        {
            realPath = servletContext.getRealPath("/music/" + filename);
        }
        System.out.println(realPath);
        //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);
        //response.setContentType("text/html;charset=utf-8");

        //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);

        //3.2设置响应头打开方式
        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[] bytes = new byte[1024 * 8];
        int len = 0;
        while((len = fis.read(bytes)) != -1)
        {
            sos.write(bytes,0,len);
        }
        fis.close();
    }

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

中文文件名的工具类

package pers.cb.web.utils;

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{
            // 其他浏览器
            filename = URLEncoder.encode(filename,"utf-8");
        }
        return filename;
    }
}