<!--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>

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

<!--文件上传配置-->
    <bean id="multipartResolver"  class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- 请求的编码格式，必须和jSP的pageEncoding属性一致，以便正确读取表单的内容，默认为ISO-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>

@RestController
public class FileController {
    //@RequestParam("file") 将name=file控件得到的文件封装成CommonsMultipartFile 对象
    //批量上传CommonsMultipartFile则为数组即可
    @RequestMapping("/upload")
    public String fileUpload(@RequestParam("file") CommonsMultipartFile file , HttpServletRequest request) throws IOException {

        //1.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);

        //2.上传路径保存设置
        String path = request.getSession().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

        //3.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("/download")
    public String downloads(HttpServletResponse response , HttpServletRequest request) throws Exception{
        //要下载的图片地址
        String  path = request.getSession().getServletContext().getRealPath("/upload");
        String  fileName = "1.jpg";

        //1、设置response 响应头
        response.reset(); //设置页面不缓存,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、 读取文件--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 "OK";
    }