文件的上传和下载~~_用户相关文件的上传和下载的功能-优快云博客

本文链接：https://blog.youkuaiyun.com/AIJXB/article/details/111321838

准备

文件上传是项目开发中最常见的功能之一,springMVC 可以很好的支持文件上传，但是
SpringMvc上下文中默认没有装配MultipartResolver,因此默认情况下其不能处理文件上传工作。
如果想使用Spring的文件上传功能，则需要在上下文中配置MultipartResolver。
前端表单要求:
为了能_上传文件，必须将表单的method设置为POST,并将enctype设置为
multipart/form-data。只有在这样的情况下，浏览器才会把用户选择的文件以二进制数据发送给服
务器;

文件上传

导入相关jar包

 <dependencies>
        <!--文件上传-->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.3</version>
        </dependency>
    <!--servlet-api导入高版本的-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>

</dependencies>

配置springmvc专属的文件上传配置

    <!--文件上传配置-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!--请求的编码格式，必须利JSP的pageEncoding属性一致，以便正确读取表单的内容，默认为IS0-8859-1 -->
        <property name="defaultEncoding" value="utf-8"/>
        <!--. 上传文件大小上限，单位为字节(10485760=10M) -->
        <property name="maxUploadSize" value="10485760"/>
        <property name="maxInMemorySize" value="40960"/>
    </bean>

index.jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>

  <form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">
    <input type="file" name="file">
    <input type="submit" value="upload">
  </form>

  </body>
</html>

controller编写

package com.lei.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import java.io.*;

@RestController
public class FileController {

@RequestMapping("/upload")
    public String upload( @RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
    //获取文件名: file. getOriginalFilename();
    String uploadFileName = file.getOriginalFilename();
    //如果文件名为空，直接回到首页!
    if ("".equals (uploadFileName)){
        return "redirect:/index.jsp";
    }
    System.out.println("上传文件名: "+uploadFileName);
    //.上:传路径保存设置
    String path = request.getServletContext(). getRealPath("/upload");
    //如果路径不存在，创建-一个
    File realPath = new File(path);
    if (!realPath. exists()){
        realPath. mkdir();
    }
    System.out.println("上传文件保存地址: "+realPath);
    InputStream is = file. getInputStream(); //文件输入流
    OutputStream os = new FileOutputStream( new File(realPath, uploadFileName)); //文 件输出流
    //读取写出
    int len = 0;
    byte[] buffer = new byte[1024];
    while ((len=is.read(buffer))!=-1){
        os .write(buffer, 0,len);
        os. flush();
    }
    os.close();
    is.close();
    return "redirect:/index.jsp";
}


    @RequestMapping("/upload2")
    public String fileUp1oad2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
        //.上:传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }
        //.上传文件地址
        System.out.println("上传文件保存地址: " + realPath);
        //通过CommonsMultipartFile的方法直接写文件(注意这个时候)
        file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));
        return "redirect:/index.jsp";
    }


}

在这里插入图片描述

上传成功

文件下载

@RequestMapping(value="/download")
    public String downloads(HttpServletResponse response,HttpServletRequest request) throws Exception {
        //要下载的图片地址
        String path = request.getServletContext().getRealPath("/upload");
        String fileName = "每日任务.txt";
        //1、设置response 响应头
        response.reset(); //设置页而不级存,清空buffer
        response.setCharacterEncoding("UTF-8"); //字符编码
        response.setContentType("multipart/ form-data"); //二进制传输数据
        //设置响应头
        response.setHeader("Content-Disposition",
                " attachment ;fileName=" + URLEncoder.encode(fileName, "UTF-8"));
        File file = new File(path, fileName);
        //2、读收文件--输入流
        InputStream input = new FileInputStream(file);
        //3、写出 文件--输出流
        OutputStream out = response.getOutputStream();
        byte[] buff = new byte[1024];
        int index = 0;
        //4、执行写出操作
        while ((index = input.read(buff)) != -1) {
            out.write(buff, 0, index);
            out.flush();
        }
        out.close();
        input.close();
        return null;
    }