監聽服務的四種實現方式，以監聽 Nacos服務為例

1.傳統方式

public void subscribe() {
    try {

            NamingService namingService = NamingFactory.createNamingService("127.0.0.1:8848"); 
            namingService.subscribe("serverName","groupName",new EventListener() {
                @Override
                public void
 
 onEvent(Event event) {
                   if (event instanceof NamingEvent) {
                        System.out.println("服務名："+((NamingEvent)event).getServiceName());
                        System.out.println("例項："+((NamingEvent)event).getInstances());
                    }
                }
            });

    } 
 
catch (NacosException e) {
        logger.error(e.getMessage(), e);
    }
} 

2.簡寫方式

public void subscribe() {
    try {

            NamingService namingService = NamingFactory.createNamingService("127.0.0.1:8848"); 
            namingService.subscribe("serverName","groupName", event -> {
                
 
if (event instanceof NamingEvent) {
                    System.out.println("服務名："+((NamingEvent)event).getServiceName());
                    System.out.println("例項："+((NamingEvent)event).getInstances());
                }
            });

    } catch (NacosException e) {
        logger.error(e.getMessage(), e);
    }
} 

3.獨立方法

public void subscribe() {
    try {

            NamingService namingService = NamingFactory.createNamingService("127.0.0.1:8848"); 
            namingService.subscribe("serverName","groupName", serviceListener);

    } catch (NacosException e) {
        logger.error(e.getMessage(), e);
    }
} 



EventListener serviceListener = (event) ->
{
    if (event instanceof NamingEvent) {
        System.out.println("服務名："+((NamingEvent)event).getServiceName());
        System.out.println("例項："+((NamingEvent)event).getInstances());
    }
};

4.獨立檔案

public void subscribe() {
    try {

            NamingService namingService = NamingFactory.createNamingService("127.0.0.1:8848"); 
            namingService.subscribe("serverName","groupName", new NacosListener());

    } catch (NacosException e) {
        logger.error(e.getMessage(), e);
    }
} 

//單獨Class類
public class NacosListener implements EventListener {
    @Override
    public void onEvent(Event event) {
        if (event instanceof NamingEvent) {
            System.out.println(((NamingEvent)event).getServiceName());
            System.out.println(((NamingEvent)event).getInstances());
        }
    }
}