Nacos如何实现服务自动注册

public class NacosServiceRegistryAutoConfiguration {
	// 注册类实现，验证我们的想法，需要用到NacosDiscoverProperties
	@Bean
	public NacosServiceRegistry nacosServiceRegistry(
			NacosDiscoveryProperties nacosDiscoveryProperties) {
		return new NacosServiceRegistry(nacosDiscoveryProperties);
	}
	// 构建注册事例，依然要用到NacosDiscoverProperties
	@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	public NacosRegistration nacosRegistration(
			NacosDiscoveryProperties nacosDiscoveryProperties,
			ApplicationContext context) {
		return new NacosRegistration(nacosDiscoveryProperties, context);
	}
	// 服务自动注册，通过上面实例化的两个类
	@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	public NacosAutoServiceRegistration nacosAutoServiceRegistration(
			NacosServiceRegistry registry,
			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
			NacosRegistration registration) {
		return new NacosAutoServiceRegistration(registry,
				autoServiceRegistrationProperties, registration);
	}
}

public class NacosAutoServiceRegistration
		extends AbstractAutoServiceRegistration<Registration> {

	private NacosRegistration registration;
	// 构造参数，关键
	public NacosAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry,
			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
			NacosRegistration registration) {
		super(serviceRegistry, autoServiceRegistrationProperties);
		this.registration = registration;
	}
  // 注册方法
  @Override
	protected void register() {
		if (!this.registration.getNacosDiscoveryProperties().isRegisterEnabled()) {
			log.debug("Registration disabled.");
			return;
		}
		if (this.registration.getPort() < 0) {
			this.registration.setPort(getPort().get());
		}
    // 调用了父类的注册方法
		super.register();
	}
}  

// 类
public abstract class AbstractAutoServiceRegistration<R extends Registration>
		implements AutoServiceRegistration, ApplicationContextAware,
		ApplicationListener<WebServerInitializedEvent> {
      
}

	@Override
	@SuppressWarnings("deprecation")
	public void onApplicationEvent(WebServerInitializedEvent event) {
    // 调用了bind方法
		bind(event);
	}
	
	@Deprecated
	public void bind(WebServerInitializedEvent event) {
		ApplicationContext context = event.getApplicationContext();
		if (context instanceof ConfigurableWebServerApplicationContext) {
			if ("management".equals(((ConfigurableWebServerApplicationContext) context)
					.getServerNamespace())) {
				return;
			}
		}
		this.port.compareAndSet(0, event.getWebServer().getPort());
    // 调用了start()方法
		this.start();
	}

	public void start() {
		if (!isEnabled()) {
			if (logger.isDebugEnabled()) {
				logger.debug("Discovery Lifecycle disabled. Not starting");
			}
			return;
		}
		
		// only initialize if nonSecurePort is greater than 0 and it isn't already running
		// because of containerPortInitializer below
		if (!this.running.get()) {
      // 时间注册之前事件
			this.context.publishEvent(
					new InstancePreRegisteredEvent(this, getRegistration()));
      // 调用了注册方法
			register();
      // 服务注册事件
			this.context.publishEvent(
					new InstanceRegisteredEvent<>(this, getConfiguration()));
			this.running.compareAndSet(false, true);
		}

	}

	protected void register() {
    // this.serviceRegistry 是我们传递进来的，
    // getRegistration() 是在NacosAutoServiceRegistration中实现的
		this.serviceRegistry.register(getRegistration());
	}

	@Override
	public void register(Registration registration) {

		if (StringUtils.isEmpty(registration.getServiceId())) {
			log.warn("No service to register for nacos client...");
			return;
		}

		String serviceId = registration.getServiceId();
		String group = nacosDiscoveryProperties.getGroup();
		// 通过registration构建Instance实例
		Instance instance = getNacosInstanceFromRegistration(registration);

		try {
      // 向服务端发送注册请求
			namingService.registerInstance(serviceId, group, instance);
			log.info("nacos registry, {} {} {}:{} register finished", group, serviceId,
					instance.getIp(), instance.getPort());
		}
		catch (Exception e) {
			log.error("nacos registry, {} register failed...{},", serviceId,
					registration.toString(), e);
			// rethrow a RuntimeException if the registration is failed.
			// issue : https://github.com/alibaba/spring-cloud-alibaba/issues/1132
			rethrowRuntimeException(e);
		}
	}