如何使用Nacos监听其他服务的上下线状态？

import com.alibaba.nacos.api.NacosFactory;
import com.alibaba.nacos.api.config.ConfigService;
import com.alibaba.nacos.api.config.listener.Listener;
import com.alibaba.nacos.api.exception.NacosException;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * 监听服务上下线状态的示例
 */
@SpringBootApplication
public class App {

    public static void main(String[] args) throws NacosException {
        SpringApplication.run(App.class, args);

        ConfigService configService = NacosFactory.createConfigService("localhost:8848");

        configService.addListener("test", "DEFAULT_GROUP", new Listener() {

            @Override
            public void receiveConfigInfo(String configInfo) {
                System.out.println("接收到服务上下线信息：" + configInfo);
            }

            @Override
            public Executor getExecutor() {
                return null;
            }
        });
    }
}