1. Write custom subscribers

The reference here is InstancesChangeNotifier This class .

import com.alibaba.nacos.api.naming.listener.NamingEvent;
import com.alibaba.nacos.client.naming.event.InstancesChangeEvent;
import com.alibaba.nacos.common.notify.listener.Subscriber;
import com.alibaba.nacos.common.notify.Event;


public class MyChangeNotifier extends Subscriber<InstancesChangeEvent> {
    

        @Override
        public void onEvent(InstancesChangeEvent event) {
    
            // TODO  Changes in subscribed services will trigger 
            //  Here we get all the information about the service cluster , Include service name 、 Information of each node .
            NamingEvent namingEvent = transferToNamingEvent(event);
        }

        @Override
        public Class<? extends Event> subscribeType() {
    
            return InstancesChangeEvent.class;
        }

        private NamingEvent transferToNamingEvent(
                InstancesChangeEvent instancesChangeEvent) {
    
            return new NamingEvent(instancesChangeEvent.getServiceName(), instancesChangeEvent.getGroupName(),
                    instancesChangeEvent.getClusters(), instancesChangeEvent.getHosts());
        }
    }

2. Register custom subscribers

//  After the project starts , Or register your subscribers when you want to register .
//  Be careful ： Register different subscriber objects multiple times , Then there will really be many same subscribers . There is no problem registering the same object multiple times . It can be understood as going to set Riga objects 
NotifyCenter.registerSubscriber(new MyChangeNotifier());

3. Subscribe to the service you want to subscribe to

Other services used in normal projects will be automatically subscribed , If you want to add additional subscriptions manually , The simplest way is to get it manually .

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.stereotype.Component;

@Component
public class Test {
    

    @Autowired
    private DiscoveryClient discoveryClient;

    public void test(){
    
    	//  This is equivalent to subscribing to the specified service  
        discoveryClient.getInstances("service-name");
    }

Subscription service , What is really called is
com.alibaba.nacos.client.naming.NacosNamingService#selectInstances(java.lang.String, java.lang.String, boolean).
complete nacos Subscription logic in com.alibaba.nacos.client.naming.core.HostReactor#getServiceInfo in