SpringMVC使用MultipartFile上传文件报错【org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.multipart.MultipartFile]: Specified class is an interface】

报错场景：

　　使用SpringMVC（或SSM框架）实现文件上传时报【 Failed to instantiate [org.springframework.web.multipart.MultipartFile]: Specified class is an interface】错，控制器代码：

 1 package com.xjs.controller;
 2 
 3 import org.apache.commons.io.FileUtils;
 4 import org.springframework.stereotype.Controller;
 5 import org.springframework.ui.Model;
 6 import org.springframework.web.bind.annotation.RequestMapping;
 7 import org.springframework.web.multipart.MultipartFile;
 8 
 9 import javax.servlet.http.HttpServletResponse;
10 import java.io.File;
11 import java.io.IOException;
12 
13 /**
14  * @ClassName:FileController
15  * @Author:微微亮
16  * @Description:
17  * @Date:2020/9/23 11:37
18  * @Version: 1.0
19  */
20 @Controller
21 @RequestMapping("/myFile")
22 public class FileController {
23 
24     @RequestMapping("/add")
25     public String upload(Model model, MultipartFile xjs) throws IOException {
26         //获取文件的名字
27         String filename = xjs.getOriginalFilename();
28         String newFileName = System.currentTimeMillis()+filename;
29         File file1 = new File("E:\myImg\"+newFileName);
30 
31         model.addAttribute("newFileName",newFileName);
32         //把文件写入相应的文件夹
33         xjs.transferTo(file1);
34         return "forward:/show.jsp";
35     }
36 
37 }

解决方法：

在参数MultipartFile前加注解@RequestParam

 1 package com.xjs.controller;
 2 
 3 import org.apache.commons.io.FileUtils;
 4 import org.springframework.stereotype.Controller;
 5 import org.springframework.ui.Model;
 6 import org.springframework.web.bind.annotation.RequestMapping;
 7 import org.springframework.web.multipart.MultipartFile;
 8 
 9 import javax.servlet.http.HttpServletResponse;
10 import java.io.File;
11 import java.io.IOException;
12 
13 /**
14  * @ClassName:FileController
15  * @Author:微微亮
16  * @Description:
17  * @Date:2020/9/23 11:37
18  * @Version: 1.0
19  */
20 @Controller
21 @RequestMapping("/myFile")
22 public class FileController {
23 
24     @RequestMapping("/add")
25     public String upload(Model model, @RequestParam("xjs")MultipartFile xjs) throws IOException {
26         //获取文件的名字
27         String filename = xjs.getOriginalFilename();
28         String newFileName = System.currentTimeMillis()+filename;
29         File file1 = new File("E:\myImg\"+newFileName);
30 
31         model.addAttribute("newFileName",newFileName);
32         //把文件写入相应的文件夹
33         xjs.transferTo(file1);
34         return "forward:/show.jsp";
35     }
36 }

另一种原因是：

springMVC的配置文件中开启注解：<mvc:annotation-driven/>

可以解决上述报错

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xmlns:context="http://www.springframework.org/schema/context"
 5        xmlns:mvc="http://www.springframework.org/schema/mvc"
 6        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
 7 
 8     <!--扫描注解-->
 9     <context:component-scan base-package="com.xjs"/>
10 
11     <!--开启注解-->
12     <mvc:annotation-driven/>
13 
14     <!--bean支持文件上传-->
15     <!--支持文件上传的bean的id是固定的，底层spring会根据这个id值来获取对象-->
16     <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
17         <!--设置文件上传的大小，value值的单位是B
18                       默认不能超过2M
19                 -->
20         <property name="maxUploadSize" value="10485760"></property>
21     </bean>
22 
23 </beans>