16. 文件上传下载

16.1 介绍

实现web开发中的文件上传功能，需完成如下二步操作：

1、在web页面中添加上传输入项

2、在servlet中读取上传文件的数据，并保存到服务器中。

如何在web页面中添加上传输入项？

<input type="file">表单用于在web页面中添加文件上传输入项，设置文件上传输入项时须注意：

1、必须要设置input输入项的name属性，否则浏览器将不会发送上传文件的数据。

2、必须把form表单的enctype属值设为multipart/form-data.

3、必须把form表单的method属性设置为post方式。设置该值后，浏览器在上传文件时，将把文件数据附带在http请求消息体中，并使用ＭＩＭＥ协议对上传的文件进行描述，以方便接收方对上传数据进行解析和处理。

如何在Servlet中读取文件上传数据，并保存到服务器中?

Request对象提供了一个getInputStream方法，通过这个方法可以读取到客户端提交过来的数据。但由于用户可能会同时上传多个文件，在servlet端编程直接读取上传数据，并分别解析出相应的文件数据是一项非常麻烦的工作。
在Servlet3.0出现之前，处理文件上传需要借助第三方组件，例如Apache的commons-fileupload组件等。而Servlet3.0出现以后就摆脱了这一问题。使用Servlet3.0可以十分方便的实现文件的上传。

16.2 commons-fileupload

由Apache提供的上传组件: 官网

首先需要创建web项目

添加依赖

  <dependencies>
    <!--单元测试-->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!--Servlet-API 编译时需要-->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.0.1</version>
      <scope>provided</scope>
    </dependency>

    <!--JSP-API 编译时需要-->
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.1</version>
      <scope>provided</scope>
    </dependency>


    <!-- lombok 帮助快速生成 setter、getter toString equals、hashcode 构造器 -->
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.12</version>
      <scope>provided</scope>
    </dependency>

    <!--jstl Apache 的标准标签库-->
    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>

    <!-- commons-fileupload 从request中解析 文件流  -->
    <dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.4</version>
    </dependency>
  </dependencies>

16.2.1 文件上传

上传页面: upload.jsp

html

<%--
  Created by IntelliJ IDEA.
  User: root
  Date: 2020/12/18
  Time: 9:11
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>



<h3>上传文件</h3>
<form method="post" enctype="multipart/form-data" action="${pageContext.request.contextPath}/up">

    <input type="file" name="file" />

    <input type="text" name="name" value=""/>
    <input type="text" name="password"   value=""/>
    <input type="submit">
</form>

</body>
</html>

配置文件用于配置上传文件目录: config.properties

properties

upload.dir=d:/upload

上传文件的Servlet

java

package com.neuedu.updown;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.ServletContext;
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;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
import java.util.Properties;

/**
 * 项目：      javawebother
 * 类名:       ${NAME}
 * 创建时间：  2020/12/18  9:29
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "FileUploadServlet", urlPatterns = "/up")
public class FileUploadServlet extends HttpServlet {

    private static String baseDir;
    static {

        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");
        Properties properties = new Properties();
        try {
            properties.load(is);

            baseDir = (String) properties.getProperty("upload.dir");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        boolean isMultipart = ServletFileUpload.isMultipartContent(request);

        if (isMultipart) {

            // Create a factory for disk-based file items
            DiskFileItemFactory factory = new DiskFileItemFactory();

            // Configure a repository (to ensure a secure temp location is used)
            ServletContext servletContext = this.getServletConfig().getServletContext();
            File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
            factory.setRepository(repository);

            // Create a new file upload handler
            ServletFileUpload upload = new ServletFileUpload(factory);
            // Parse the request
            try {

                //表单域， input【text、file】
                List<FileItem> items = upload.parseRequest(request);
                for (FileItem item : items) {

                    if(item.isFormField()) { // text password checkbox ...
                        String name = item.getFieldName() ;// 控件的名字 input[name= ??? ]
                        String value = item.getString(); // 控件的值 input[value= ??? ]
                        System.out.println(name+"\t"+value);
                    }else{ //   type =  file

//                        String fileName = item.getFieldName(); //原始的文件名
                        String fileName = item.getName(); //原始的文件名
                        File dist = new File(baseDir,fileName);
                        item.write(dist);//转储到 baseDir【D:/upload】


                        String now = "";//new Date();
                        String clientHost = request.getRemoteHost();
                        long size = item.getSize();

                        String info = String.format("host:%s\t time:%s, name:%s\t size:%s",
                                clientHost,
                                new Date().toString(),
                                fileName,
                                String.valueOf(size)
                        );

                        //上传文件的信息
                        System.out.println(info);
                    }
                }
            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }


        } else {//普通的表单处理
            //            request.getParameter()

        }

    }


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

16.2.2 保存上传文件信息

创建数据库

/*
SQLyog Ultimate v12.08 (64 bit)
MySQL - 5.7.18 : Database - upload
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`upload` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `upload`;

/*Table structure for table `upload_files` */

DROP TABLE IF EXISTS `upload_files`;

CREATE TABLE `upload_files` (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键',
  `origin_name` varchar(500) NOT NULL COMMENT '原始文件名',
  `path` varchar(500) NOT NULL COMMENT '文件系统中的相对路径',
  `upload_time` datetime DEFAULT CURRENT_TIMESTAMP COMMENT '上传时间',
  `size` int(11) DEFAULT NULL COMMENT '文件大小',
  `ip` varchar(100) DEFAULT NULL COMMENT '上传ip',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/*Data for the table `upload_files` */

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

添加JDBCUTIL依赖

xml

 <dependency>
      <groupId>com.neuedu</groupId>
      <artifactId>jdbcutil</artifactId>
      <version>1.0</version>
    </dependency>

jdbc.properties

properties

jdbc.url=jdbc:mysql://127.0.0.1:3306/upload?characterEncoding=utf8&useUnicode=true&useSSL=false
jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.username=root
jdbc.password=root

实体类

java

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UploadFile {

    private Integer id;

    private String path;
    private String ip;
    private Integer size;

    @Column("origin_name")
    private String originName;

    @Column("upload_time")
    private String uploadTime;
    
}

UploadFileDao层代码

java

package com.neuedu.updown.dao;

import com.neuedu.updown.entity.UploadFile;
import com.neuedu.util.JDBCUtil;

import java.util.List;

/**
 * 项目：      javawebother
 * 类名:       UploadFileDao
 * 创建时间：  2020/12/18  10:08
 * 描述 :
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
public class UploadFileDao {

    /**
     * 查询列表
     * @return
     */
    public List<UploadFile> selectList(){
        String sql = " select * from  upload_files ";
        return JDBCUtil.executeQuery(sql,UploadFile.class);
    }

    /**
     * 根据主键查询信息
     * @param id
     * @return
     */
    public UploadFile  getOne(Integer id){
        String sql = " select * from upload_files where id = ? ";
        return JDBCUtil.getOne(sql,UploadFile.class,id);
    }


    /**
     * 保存信息
     * @param uploadFile
     * @return
     */
    public boolean insert(UploadFile uploadFile){
        String sql = "insert into upload_files( origin_name,  path, size, ip ) values(?,?,?,?) ";
        return JDBCUtil.executeUpdate(sql,
                uploadFile.getOriginName(),
                uploadFile.getPath(),
                uploadFile.getSize(),
                uploadFile.getIp()
                );
    }
}

service层代码

java

package com.neuedu.updown.service;

import com.neuedu.updown.dao.UploadFileDao;
import com.neuedu.updown.entity.UploadFile;

import java.util.List;

/**
 * 项目：      javawebother
 * 类名:       UploadFileService
 * 创建时间：  2020/12/18  10:15
 * 描述 :     业务层
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
public class UploadFileService {

    private UploadFileDao uploadFileDao = new UploadFileDao();

    /**
     * 查集合
     * @return
     */
    public List<UploadFile> list(){
        return uploadFileDao.selectList();
    }

    /**
     * 查询一个
     * @param id
     * @return
     */
    public UploadFile  getById(Integer id){
        return  uploadFileDao.getOne(id);
    }


    /**
     * 保存信息
     * @param uploadFile
     * @return
     */
    public boolean  save(UploadFile uploadFile){
        return  uploadFileDao.insert(uploadFile);
    }

}

在controller中上传的时将信息保存到数据库中

java

package com.neuedu.updown;

import com.neuedu.updown.entity.UploadFile;
import com.neuedu.updown.service.UploadFileService;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.ServletContext;
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;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
import java.util.Properties;
import java.util.UUID;

/**
 * 项目：      javawebother
 * 类名:       ${NAME}
 * 创建时间：  2020/12/18  9:29
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "FileUploadServlet", urlPatterns = "/up")
public class FileUploadServlet extends HttpServlet {


    private UploadFileService uploadFileService = new UploadFileService();

    private static String baseDir;
    static {

        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");
        Properties properties = new Properties();
        try {
            properties.load(is);

            baseDir = (String) properties.getProperty("upload.dir");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        boolean isMultipart = ServletFileUpload.isMultipartContent(request);

        if (isMultipart) {

            // Create a factory for disk-based file items
            DiskFileItemFactory factory = new DiskFileItemFactory();

            // Configure a repository (to ensure a secure temp location is used)
            ServletContext servletContext = this.getServletConfig().getServletContext();
            File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
            factory.setRepository(repository);

            // Create a new file upload handler
            ServletFileUpload upload = new ServletFileUpload(factory);
            // Parse the request
            try {

                //表单域， input【text、file】
                List<FileItem> items = upload.parseRequest(request);
                for (FileItem item : items) {

                    if(item.isFormField()) { // text password checkbox ...
                        String name = item.getFieldName() ;// 控件的名字 input[name= ??? ]
                        String value = item.getString(); // 控件的值 input[value= ??? ]
                        System.out.println(name+"\t"+value);
                    }else{ //   type =  file

//                        String fileName = item.getFieldName(); //原始的文件名
                        String fileName = item.getName(); //原始的文件名


                        String ext = fileName.substring(fileName.lastIndexOf("."));
                        String newFileName = UUID.randomUUID().toString().replace("-","")+ext;
                        File dist = new File(baseDir,newFileName); //使用uuid 生成不重复的 文件名
                        item.write(dist);//转储到 baseDir【D:/upload】


                        String now = "";//new Date();
                        String clientHost = request.getRemoteHost();
                        long size = item.getSize();

                        String info = String.format("host:%s\t time:%s, name:%s\t size:%s",
                                clientHost,
                                new Date().toString(),
                                fileName,
                                String.valueOf(size)
                        );

                        //上传文件的信息
                        System.out.println(info);


                        UploadFile uploadFile = new UploadFile();
                        uploadFile.setIp(clientHost);
                        uploadFile.setOriginName(fileName);
                        uploadFile.setPath(newFileName);
                        uploadFile.setSize((int) size);

                        uploadFileService.save(uploadFile);

                    }


                }



            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }


        } else {//普通的表单处理
            //            request.getParameter()

        }
		  //查询
        response.sendRedirect(request.getContextPath()+"/filelist");

    }


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

展示文件列表Controller

java

package com.neuedu.updown;

import com.neuedu.updown.entity.UploadFile;
import com.neuedu.updown.service.UploadFileService;

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.IOException;
import java.util.List;

/**
 * 项目：      javawebother
 * 类名:       ${NAME}
 * 创建时间：  2020/12/18  11:04
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 * http://127.0.0.1:8080/web/filelist
 */
@WebServlet(name = "FileListServlet",urlPatterns = "/filelist")
public class FileListServlet extends HttpServlet {
    UploadFileService uploadFileService = new UploadFileService();
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //跳转到 列表页面

        List<UploadFile> list = uploadFileService.list();

        request.setAttribute("list",list);
        request.getRequestDispatcher("file_list.jsp").forward(request,response);
    }

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

展示列表的jsp

html

<%@ page import="com.neuedu.updown.entity.UploadFile" %>
<%@ page import="java.util.List" %><%--
  Created by IntelliJ IDEA.
  User: root
  Date: 2020/12/18
  Time: 10:59
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<%

    List<UploadFile> list = (List<UploadFile>) request.getAttribute("list");
%>

<a href="${pageContext.request.contextPath}/upload.jsp">上传文件</a>

<table cellspacing="0" cellpadding="0" border="1" width="80%">
    <tr>
        <td>序号</td>
        <td>原始文件名</td>
        <td>上传时间</td>
        <td>文件大小</td>
        <td>上传ip</td>
        <td>下载</td>
    </tr>

    <%
        for (int i = 0; i < list.size(); i++) {
            UploadFile upload = list.get(i);

    %>
    <tr>
        <td><%=(i + 1)%>
        </td>
        <td><%=upload.getOriginName()%>
        </td>
        <td><%=upload.getUploadTime()%>
        </td>
        <td><%=upload.getSize()%>
        </td>
        <td><%=upload.getIp()%>
        </td>
        <td><a href="${pageContext.request.contextPath}/download?id=<%=upload.getId()%>">下载</a></td>
    </tr>


    <%
        }
    %>


</table>


</body>
</html>

16.2.3 文件下载

通过Serlvet将用户选择下载的文件，通过response对象输出流，输出到客户端浏览器，提供下载。

Content-Disposition 消息头指示回复的内容该以何种形式展示，是以内联的形式（即网页或者页面的一部分），还是以附件的形式下载并保存到本地。

java

response.addHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(uploadFile.getOriginName(),"utf-8") +"");

下载的Controller

java

package com.neuedu.updown;

import com.neuedu.updown.entity.UploadFile;
import com.neuedu.updown.service.UploadFileService;

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.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;
import java.util.Properties;

/**
 * 项目：      javawebother
 * 类名:       ${NAME}
 * 创建时间：  2020/12/18  11:16
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 *
 *  http://127.0.0.1:8080/web/download?id=3
 *
 *
 *
 */
@WebServlet(name = "FileDownLoadServlet",urlPatterns = "/download")
public class FileDownLoadServlet extends HttpServlet {

    UploadFileService uploadFileService = new UploadFileService();


    private static String baseDir;
    static {

        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");
        Properties properties = new Properties();
        try {
            properties.load(is);

            baseDir = (String) properties.getProperty("upload.dir");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }




    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    //设置header信息 ，通知浏览器，输出文件的类型

        String id = request.getParameter("id");

        UploadFile uploadFile = uploadFileService.getById(Integer.parseInt(id));



        response.addHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(uploadFile.getOriginName(),"utf-8") +"");
        ServletOutputStream out = response.getOutputStream();

        String fileName = uploadFile.getPath();

        File downloadFile = new File(baseDir,fileName);

        FileInputStream fis = new FileInputStream(downloadFile);
        byte[] buffer = new byte[1024];

        int len = -1;
        while ( (len = fis.read(buffer)) != -1){
            out.write(buffer,0,len);
            out.flush();

        }

        out.close();
    }

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

上传文件的列表

点击【下载】后Chrome浏览器的效果

16.3 Servlet3.0 上述环境相同

修改FileUploadServlet

java

package com.neuedu.updown;

import com.neuedu.updown.entity.UploadFile;
import com.neuedu.updown.service.UploadFileService;


import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
import java.util.Properties;
import java.util.UUID;

/**
 * 项目：      javawebother
 * 类名:       ${NAME}
 * 创建时间：  2020/12/18  9:29
 * 描述 :     ${dc}
 * 作者 :     张金山
 * QQ :     314649444
 * Site:      https://jshand.gitee.io
 */
@WebServlet(name = "FileUploadServlet", urlPatterns = "/up")
@MultipartConfig
public class FileUploadServlet extends HttpServlet {


    private UploadFileService uploadFileService = new UploadFileService();

    private static String baseDir;
    static {

        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");
        Properties properties = new Properties();
        try {
            properties.load(is);

            baseDir = (String) properties.getProperty("upload.dir");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        Part part = request.getPart("file");

//        request.getParts()
        String contentDisposition = part.getHeader("content-disposition"); // form-data; name="file"; filename="xxxx"

        //原始的文件名
        String fileName = contentDisposition.split("filename")[1] ;//  ="xxxx"

        fileName = fileName.substring(2,fileName.length()-1);

        System.out.println("fileName:"+fileName);


        String ext = fileName.substring(fileName.lastIndexOf("."));
        String newFileName = UUID.randomUUID().toString().replace("-", "") + ext;
        File dist = new File(baseDir, newFileName); //使用uuid 生成不重复的 文件名
        part.write(dist.getPath());//转储到 baseDir【D:/upload】

        String now = "";//new Date();
        String clientHost = request.getRemoteHost();
        long size = part.getSize();

        String info = String.format("host:%s\t time:%s, name:%s\t size:%s",
                clientHost,
                new Date().toString(),
                fileName,
                String.valueOf(size)
        );

        //上传文件的信息
        System.out.println(info);


        UploadFile uploadFile = new UploadFile();
        uploadFile.setIp(clientHost);
        uploadFile.setOriginName(fileName);
        uploadFile.setPath(newFileName);
        uploadFile.setSize((int) size);

        uploadFileService.save(uploadFile);


        //查询
        response.sendRedirect(request.getContextPath()+"/filelist");


    }



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

16. 文件上传下载 ​

16.1 介绍 ​

16.2 commons-fileupload ​

16.2.1 文件上传 ​

16.2.2 保存上传文件信息 ​

16.2.3 文件下载 ​

16.3 Servlet3.0 上述环境相同 ​

16. 文件上传下载

16.1 介绍

16.2 commons-fileupload

16.2.1 文件上传

16.2.2 保存上传文件信息

16.2.3 文件下载

16.3 Servlet3.0 上述环境相同