一、配置spring-mvc

<!-- 配置多媒体文件解析器 -->  
<bean id="multipartResolver"  
    class="org.springframework.web.multipart.commons.CommonsMultipartResolver">  
    <!-- 设定默认编码 -->  
    <property name="defaultEncoding" value="UTF-8"></property>  
    <!-- 设定文件上传的最大值2MB， 2\*1024\*1024 -->  
    <property name="maxUploadSize" value="2097152"></property>  
    <!--resolveLazily属性启用是为了推迟文件解析，以便在UploadAction 中捕获文件大小异常-->  
    <property name="resolveLazily" value="true"/>  
</bean>

实现文件上传和下载需要添加依赖

commons-fileupload commons-fileupload 1.3

commons-io commons-io 1.3.2

二、实现文件上传

1、文件上传Controller

/\*\*  
               \* 文件上传功能  
  \* @param file  
  \* @return  
  \* @throws IOException  
  \*/  
@RequestMapping(value="/upload",method=RequestMethod.POST)  
public @ResponseBody  ModelAndView upload(@RequestParam("file")MultipartFile file, HttpServletRequest request) throws IOException {  
   ModelAndView mv = new ModelAndView("message");  
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSS");  
    String res = sdf.format(new Date());

    // uploads文件夹位置  
    String rootPath = request.getSession().getServletContext().getRealPath("WEB-INF/upload");  
    // 原始名称  
    String originalFileName = file.getOriginalFilename();  
    // 新文件名  
    String newFileName = "sliver" + res + originalFileName.substring(originalFileName.lastIndexOf("."));  
    // 创建年月文件夹  
    Calendar date = Calendar.getInstance();  
    File dateDirs = new File(date.get(Calendar.YEAR) + File.separator + (date.get(Calendar.MONTH)+1));

    // 新文件  
    File newFile = new File(rootPath + File.separator + dateDirs + File.separator + newFileName);  
    // 判断目标文件所在目录是否存在  
    if( !newFile.getParentFile().exists()) {  
        // 如果目标文件所在的目录不存在，则创建父目录  
        newFile.getParentFile().mkdirs();  
    }  
    System.out.println(newFile);  
    // 将内存中的数据写入磁盘  
    file.transferTo(newFile);  
    // 完整的url

   String fileUrl = date.get(Calendar.YEAR) + "/" + (date.get(Calendar.MONTH)+1) + "/" + newFileName;  
   mv.addObject("path", fileUrl);  
   return  mv;  
}

2、fileupoad.jsp

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>

选择文件:

---

3、实现结果

三、实现文件下载

1、下载的controller

 /\*\*  
 \* 文件下载功能  
 \* @param request  
 \* @param response  
 \* @throws Exception  
 \*/  
@RequestMapping("/down")  
public void down(HttpServletRequest request,HttpServletResponse response) throws Exception{  
    //模拟文件，myfile.txt为需要下载的文件  
    String fileName = request.getSession().getServletContext().getRealPath("WEB-INF/upload/2020/1")+"/sliver20200115164910583.txt";  
    //获取输入流  
    InputStream bis = new BufferedInputStream(new FileInputStream(new File(fileName)));  
    //假如以中文名下载的话  
    String filename = "下载文件.txt";  
    //转码，免得文件名中文乱码  
    filename = URLEncoder.encode(filename,"UTF-8");  
    //设置文件下载头  
    response.addHeader("Content-Disposition", "attachment;filename=" + filename);  
    //1.设置文件ContentType类型，这样设置，会自动判断下载文件类型  
    response.setContentType("multipart/form-data");  
    BufferedOutputStream out = new BufferedOutputStream(response.getOutputStream());  
    int len = 0;  
    while((len = bis.read()) != -1){  
        out.write(len);  
        out.flush();  
    }  
    out.close();  
}  

2、实现过程

每天学一点、日后往学习深点的实现过程。