首页 > 其他分享> > Commons-FileUpload

Commons-FileUpload

2021-06-20 21:59:15 作者：互联网

Commons-FileUpload组件文件下载

1）原理

a.请求（超链接），请求Servlet

b.Servlet通过文件地址将文件转为输入流，读到servlet

c.通过输出流将刚才转为输入流的文件发送给用户

2）jsp代码

<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" language="java" %>
<html>
<body>
<h2>Hello World!</h2>

<a href="/DownloadServlet?fileName=fortunate.png">fortunate</a>
</body>
</html>

3）servlet代码

package student.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.IOException;
import java.io.InputStream;
import java.net.URLEncoder;

public class DownloadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        //获取需要下载的文件名（form,href,servlet?）
        String fileName = req.getParameter("fileName");
        //下载文件：需要设置响应消息头
        //MIME类型，二进制文件
        resp.addHeader("content-Type","application/octet-stream");
        //filename包含后缀（文件名=文件名+后缀名）
        resp.addHeader("content-Disposition","attachment;filename="+fileName);
        resp.addHeader("content-Disposition","attachment;filename="+URLEncoder.encode(fileName,"UTF-8"));

        //根据文件的地址，将文件转为输入流（字节流）
        InputStream in= getServletContext().getResourceAsStream("/res/fortunate.png");

        //输出流
        ServletOutputStream out = resp.getOutputStream();
        //the buffer into which the data is read.缓冲区
        byte[] bytes = new byte[10];
        int len = -1;
        in.read();
        while ((len = in.read(bytes))!=-1){
            out.write(bytes,0,len);
        }
        out.close();
        in.close();


    }

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

标签：文件,FileUpload,resp,req,Commons,import,servlet,javax
来源： https://blog.csdn.net/csdn099/article/details/118075832