文件的上传和下载

最新推荐文章于 2022-02-16 11:18:18 发布

Monsterera

最新推荐文章于 2022-02-16 11:18:18 发布

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分类专栏： java学习记录文章标签： java servlet tomcat

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本文介绍了使用Java Servlet进行文件上传和下载的基本操作，详细阐述了相关步骤和技术要点。

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文件的上传和下载

这个星期学习了蛮多东西,我准备吧简单写一个文件的上传和下载.

在这里插入图片描述

<%--
  Created by IntelliJ IDEA.
  User: liqiuyang
  Date: 2020/8/26
  Time: 9:03
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=GB2312" language="java" %>
<html>
  <head>
    <title></title>
    <meta charset="GB2312">
  </head>
  <body>
  <form action="upload" enctype="multipart/form-data" method="post">
    单个文件上传:<input type="file" name="myFile"><br>
    username:<input type="text" name="myFile"><br>
    <input type="submit" value="上传">
  </form>
  <form action="upload" enctype="multipart/form-data" method="post">
    多个文件上传:<input type="file" name="myFile"><br>
                <input type="file" name="myFile"><br>
    <input type="submit" value="上传">
  </form>
  </body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: liqiuyang
  Date: 2020/8/26
  Time: 10:37
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
    <style>
        .card{
            width: 250px;
            height: 250px;
            float: left;
        }
        img{
            width: 250px;
            height: 250px;
        }
        p{
            width:250px;
            height: 20px;
        }
        p a{
            width:250px;
            height: 20px;
            line-height: 20px;
            margin-left: 40%;
        }
    </style>
</head>
<body>
    <c:set var="types" value="'jpg','jpeg','png'"></c:set>
    <c:forEach var="f" items="${files}">
        <c:if test="${f.getName().endsWith('.jpg')}">
    <div class="card">
        <%--在jsp中获取容器中的目录位置
        req.getServletContext().getPath()--%>
        <img src="${pageContext.servletContext.contextPath}/upload/${f.getName()}">
        <p>
            ${f.getName().substring(36)}
            <br>
                <%--向servlet提交完整的文件名--%>
            <a href="down?fileName=${f.getName()}">下载</a>
        </p>
    </div>
        </c:if>
    </c:forEach>

</body>
</html>

package com.softeem.file.update;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.stream.events.EndDocument;
import java.io.*;
import java.net.URLEncoder;

/**
 * @Author liqiuyang 2020/8/26 11:37
 */
@WebServlet("/down")
public class DownLoadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fileName = req.getParameter("fileName");
        System.out.println(fileName);
        //设置相应头,要求客户端浏览器激活下载功能
        //mime:content-disposition
        resp.setHeader("content-disposition","attachment;fileName="+ URLEncoder.encode(fileName,"utf-8"));
        //io操作
        String path = req.getServletContext().getRealPath("upload")+ File.separator+fileName;
        //输入流
        InputStream input = new FileInputStream(path);
        //输出流
        OutputStream out= resp.getOutputStream();

        //缓冲区
        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len=input.read(buffer))!=-1){
            out.write(buffer);
        }
        input.close();
        out.close();
    }
}

package com.softeem.file.update;

import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.util.Collection;
import java.util.UUID;

@WebServlet("/upload")
@MultipartConfig  //该servlet可以处理二进制数据
public class FileUploadServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        //直接通过request对象获取文件对象
        Part part = request.getPart("myFile");
        Collection<Part> parts = request.getParts();
        if(parts.size()==1) {
            //获取提交的文件名
            String fileName = part.getSubmittedFileName();
            String header = part.getHeader("content-disposition");
            System.out.println(header);
            //获取提交的文件大小
            long size = part.getSize();
            //获取提交的文件类型
            String type = part.getContentType();
            System.out.println(fileName);
            System.out.println(size);

            //保存改文件
            //如果访问容器中的目录
            String path = request.getServletContext().getRealPath("upload");
            System.out.println(path);
            //设置文件名,防止文件覆盖
            String filePath = path + File.separator + UUID.randomUUID() + fileName;
            part.write(filePath);
        }else{
            parts.forEach(p->{
                String path = request.getServletContext().getRealPath("upload");
                String fileName = p.getSubmittedFileName();
                try {
                    p.write(path+File.separator+UUID.randomUUID()+fileName);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            });
        }
        //控制器
        response.sendRedirect("/getFiles");
    }

}

package com.softeem.file.update;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;

/**
 * @Author liqiuyang 2020/8/26 10:45
 */
@WebServlet("/getFiles")
public class GetFiles extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        File f = new File(req.getServletContext().getRealPath("upload"));
        //获取upload下所有文件
        File[] files = f.listFiles();
        req.setAttribute("files",files);
        req.getRequestDispatcher("download.jsp").forward(req,resp);

    }
}