一、文件上传

1.1 导入pom依赖

 <commons-fileupload.version>1.3.3</commons-fileupload.version><dependency><groupId>commons-fileupload</groupId><artifactId>commons-fileupload</artifactId><version>${commons-fileupload.version}</version></dependency>

1.2 配置文件上传解析器

在spring-mvc.xml文件中添加文件上传解析器。

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"><!-- 必须和用户JSP 的pageEncoding属性一致，以便正确解析表单的内容 --><property name="defaultEncoding" value="UTF-8"></property><!-- 文件最大大小(字节) 1024*1024*50=50M--><property name="maxUploadSize" value="52428800"></property><!--resolveLazily属性启用是为了推迟文件解析，以便捕获文件大小异常--><property name="resolveLazily" value="true"/>
</bean>

这段代码是一个Spring框架的配置，用于处理文件上传功能。它定义了一个名为multipartResolver的Bean，使用org.springframework.web.multipart.commons.CommonsMultipartResolver类来处理文件上传。其中设置了默认的编码方式为UTF-8，文件的最大大小为50MB，并启用了懒解析模式。这段代码的作用是配置文件上传的相关参数。

1.3 设置文件上传表单

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><base href="${pageContext.request.contextPath }"><title>文件上传</title>
</head>
<body>
<form action="/file/upload" method="post" enctype="multipart/form-data"><label>编号：</label><input type="text" name="id" readonly="readonly" value="${param.id}"/><br/><label>图片：</label><input type="file" name="imgFile"/><br/><input type="submit" value="上传图片"/>
</form>
</body>
</html>

1.4 实现文件上传

（1） 设计表
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(2) 配置generatorConfig.xml，并生成代码

   <table schema="" tableName="file_upload" domainObjectName="UploadFile"enableCountByExample="false" enableDeleteByExample="false"enableSelectByExample="false" enableUpdateByExample="false"></table>

（3） 创建业务层

（4） 配置resource.properties

#本地路径
dir=D:/upload/
#服务器路径
server=/upload/

(5) 配置文件读取工具类

package com.xqx.utils;import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;public class PropertiesUtil {public static String getValue(String key) throws IOException {Properties p = new Properties();InputStream in = PropertiesUtil.class.getResourceAsStream("/resource.properties");p.load(in);return p.getProperty(key);}
}

（6） 配置项目与映射地址
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(7) 编写控制器

package com.xqx.web;import com.xqx.biz.UploadFileBiz;
import com.xqx.model.UploadFile;
import com.xqx.utils.PageBean;
import com.xqx.utils.PropertiesUtil;
import org.apache.commons.io.FileUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;
import java.util.List;@Controller
@RequestMapping("/file")
public class UploadFileController {@Autowiredprivate UploadFileBiz UploadFileBiz;/*新增方法*/@RequestMapping("/add")public String save(UploadFile UploadFile, HttpServletRequest request) {UploadFileBiz.insertSelective(UploadFile);return "redirect:list";}/*删除方法*/@RequestMapping("/del/{id}")public String del(@PathVariable("id") Integer id) {UploadFileBiz.deleteByPrimaryKey(id);return "redirect:/file/list";}/*修改方法*/@RequestMapping("/edit")public String edit(UploadFile UploadFile, HttpServletRequest request) {UploadFileBiz.updateByPrimaryKeySelective(UploadFile);return "redirect:list";}/*查询方法*/@RequestMapping("/list")public String list(UploadFile UploadFile, HttpServletRequest request) {PageBean pageBean = new PageBean();pageBean.setRequest(request);List<UploadFile> UploadFiles = UploadFileBiz.listPager(UploadFile, pageBean);
//        ModelAndView modelAndView = new ModelAndView();
//        modelAndView.addObject("UploadFiles", UploadFiles);
//        modelAndView.addObject("pageBean", pageBean);
//        modelAndView.setViewName("UploadFile/list");request.setAttribute("UploadFiles", UploadFiles);request.setAttribute("pageBean", pageBean);return "file/list";}/*数据回显*/@RequestMapping("/preSave")public String preSave(UploadFile UploadFile, HttpServletRequest request) {if (UploadFile != null && UploadFile.getId() != null && UploadFile.getId() != 0) {UploadFile img = UploadFileBiz.selectByPrimaryKey(UploadFile.getId());request.setAttribute("img", img);}return "file/edit";}/*图片上传*/@RequestMapping("upload")public String upload(UploadFile img,MultipartFile imgFile) throws IOException {//读取配置文夹本地路径和服务器路径String dir = PropertiesUtil.getValue("dir");String server = PropertiesUtil.getValue("server");//利用MultipartFile类接受前端传递到后台的文件System.out.println("文件名："+imgFile.getOriginalFilename());System.out.println("文件类型："+imgFile.getContentType());//将文件转成流写入到服务器FileUtils.copyInputStreamToFile(imgFile.getInputStream(),new File(dir+imgFile.getOriginalFilename()));//通过对象将图片保存到数据库img.setImg(server+imgFile.getOriginalFilename());UploadFileBiz.updateByPrimaryKeySelective(img);return "redirect:list";}
}

（8） 编写jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="w" uri="http://jsp.xqx.cn" %>
<html>
<head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><linkhref="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.css"rel="stylesheet"><scriptsrc="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.0/js/bootstrap.js"></script><base href="${pageContext.request.contextPath }"><title></title><style type="text/css">.page-item input {padding: 0;width: 40px;height: 100%;text-align: center;margin: 0 6px;}.page-item input, .page-item b {line-height: 38px;float: left;font-weight: 400;}.page-item.go-input {margin: 0 10px;}</style>
</head>
<body>
<form class="form-inline"action="/file/list" method="post"><div class="form-group mb-2"><input type="text" class="form-control-plaintext" name="name"placeholder="请输入用户名称"></div><button type="submit" class="btn btn-primary mb-2">查询</button><a class="btn btn-primary mb-2" href="/file/preSave">新增</a>
</form><table class="table table-striped"><thead><tr><th scope="col">ID</th><th scope="col">用户</th><th scope="col">图片</th></tr></thead><tbody><c:forEach var="i" items="${uploadImgs }"><tr><td>${i.id }</td><td>${i.name }</td><td><img src="${i.img }" style="width: 200px;height: 100px;"></td><td><a href="/file/preSave?id=${i.id}">修改</a><a href="/file/del/${i.id}">删除</a><a href="/page/file/upload?id=${i.id}">图片上传</a><a href="/file/download?id=${i.id}">图片下载</a></td></tr></c:forEach></tbody>
</table>
<!-- 这一行代码就相当于前面分页需求前端的几十行了 -->
<w:page pageBean="${pageBean }"></w:page></body>
</html>

在这里插入图片描述

二、文件下载

根据传入的文件id查询对应的文件信息，然后根据文件路径读取文件内容，并将文件内容和设置好的HTTP头信息封装成一个ResponseEntity对象，最后返回给客户端进行文件下载。

   @RequestMapping("/download")public ResponseEntity<byte[]> download(UploadImg uploadImg, HttpServletRequest req){try {//先根据文件id查询对应图片信息UploadImg img = this.uploadImgBiz.selectByPrimaryKey(uploadImg.getId());String diskPath = PropertiesUtil.getValue("dir");String reqPath = PropertiesUtil.getValue("server");//上面获取的数据库地址，需要转换才能下载成本地路径String realPath = img.getImg().replace(reqPath,diskPath);String fileName = realPath.substring(realPath.lastIndexOf("/")+1);//下载关键代码File file=new File(realPath);HttpHeaders headers = new HttpHeaders();//http头信息String downloadFileName = new String(fileName.getBytes("UTF-8"),"iso-8859-1");//设置编码headers.setContentDispositionFormData("attachment", downloadFileName);headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);//MediaType:互联网媒介类型  contentType：具体请求中的媒体类型信息return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),headers, HttpStatus.OK);}catch (Exception e){e.printStackTrace();}return null;}

三、多文件上传

//多文件上传@RequestMapping("/uploads")public String uploads(HttpServletRequest req, Music music, MultipartFile[] files){try {StringBuffer sb = new StringBuffer();for (MultipartFile cfile : files) {//思路：//1) 将上传图片保存到服务器中的指定位置String dir = PropertiesUtil.getValue("dir");String server = PropertiesUtil.getValue("server");String filename = cfile.getOriginalFilename();FileUtils.copyInputStreamToFile(cfile.getInputStream(),new File(dir+filename));sb.append(filename).append(",");}System.out.println(sb.toString());} catch (Exception e) {e.printStackTrace();}return "redirect:list";}