如下

@Bean
public MultipartResolver multipartResolver(){
    CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
    return commonsMultipartResolver;
}

方法所在类：public class WebConfig implements WebMvcConfigurer {}

报错

HTTP Status 500 – Internal Server Error

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'multipartResolver' defined in com.guigu.config.WebConfig: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.web.multipart.MultipartResolver]: Factory method 'multipartResolver' threw exception; nested exception is java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItemFactory

你这个错误报的是类不存在啊，导包有问题吧
java.lang.NoClassDefFoundError: org/apache/commons/fileupload/FileItemFactory

看看你类上面是不是未写注解@component,或者没有包扫描注解 @ComponentScan