Spring Multipartfile转file类型(不生成临时文件，直接转换)

转换方式

引入pom

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>

CommonsMultipartFile commonsmultipartfile = (CommonsMultipartFile) multipartFile;
DiskFileItem diskFileItem = (DiskFileItem) commonsmultipartfile.getFileItem();
File file = diskFileItem.getStoreLocation();

转换时可能遇到问题

org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile cannot be cast to org.springframework.web.multipart.commons.CommonsMultipartFile

错误意思是两个对象无法进行强转，出错的代码如下：

CommonsMultipartFile commonsMultipartFile = (CommonsMultipartFile) multipartFile;

解决方案：
注入CommonsMultipartResolver

    @Bean(name = "multipartResolver")
    public CommonsMultipartResolver getCommonsMultipartResolver() {
        CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver();
        multipartResolver.setMaxUploadSize(20971520); //最大内存大小
        multipartResolver.setMaxInMemorySize(1024); //上传文件最小限制
        return multipartResolver;
    }

配置文件添加

spring:
  servlet:
    multipart:
      enabled: true

org.apache.commons.fileupload.disk.DiskFileItem cannot be cast to org.apache.tomcat.util.http.fileupload.disk.DiskFileItem

DiskFileItem包引错了
正常应该引用

import org.apache.commons.fileupload.disk.DiskFileItem;