private String getFileName(String name, String extension) {
		if (!StringUtils.hasLength(extension)) {
			return name;
		}
		if (!StringUtils.hasLength(name)) {
			return extension;
		}
		int idx = name.lastIndexOf(DOT);
		if (idx > 0 && idx < name.length() - 1) {
			String ext = name.substring(idx + 1);
			if (extension.equalsIgnoreCase(ext)) {
				return name;
			}
		}
		return name + DOT + 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