private String resolveNamespace() {
		if (DEFAULT_NAMESPACE.equals(this.namespace)) {
			log.info("set nacos config namespace 'public' to ''");
			return "";
		}
		else {
			return Objects.toString(this.namespace, "");
		}
	}
refer
https://github.com/alibaba/spring-cloud-alibaba/issues/2872
https://github.com/alibaba/spring-cloud-alibaba/issues/2869 .
spring-cloud-alibaba-starters/spring-alibaba-nacos-config/src/main/java/com/alibaba/cloud/nacos/NacosConfigProperties.java