docs: private static String formatDate(Object dateObj, String format) {
  		if (StrUtil.isNotBlank(format)) {
  			final Date date = (dateObj instanceof Date) ? (Date)dateObj : ((Calendar)dateObj).getTime();
  			//用户定义了日期格式
  			return DateUtil.format(date, format);
  		}
  		
  		//默认使用时间戳
  		return String.valueOf((dateObj instanceof Date) ? ((Date)dateObj).getTime() : ((Calendar)dateObj).getTimeInMillis());
  	}