public String getFileExtension(String name) {
		if (!StringUtils.hasLength(name)) {
			return DEFAULT_EXTENSION;
		}
		int idx = name.lastIndexOf(DOT);
		if (idx > 0 && idx < name.length() - 1) {
			return name.substring(idx + 1);
		}
		return DEFAULT_EXTENSION;
	}
@param name filename
@return file extension, default {@code DEFAULT_EXTENSION} if don't get
spring-cloud-alibaba-starters/spring-alibaba-nacos-config/src/main/java/com/alibaba/cloud/nacos/parser/NacosDataParserHandler.java