文件上传
1：单个文件上传
public static void uploadFile(MultipartFile file,String url) {
OssTemplate ossTemplate = SpringContextHolder.getBean(OssTemplate.class);
OssProperties ossProperties = SpringContextHolder.getBean(OssProperties.class);
ossTemplate.putObject(ossProperties.getBucketName(), url,
file.getInputStream(), file.getSize(), file.getContentType());
}