Nacos客户端入口
首先在我们使用Nacos时，会在客户端引入对应的依赖，例如需要Nacos的注册中心功能需要引入
<!--nacos-discovery 注册中心依赖--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency>
而熟悉Springboot的自然知道，为什么引用一个starter就能引入对应的功能？这离不开Springboot的自动配置功能，这也是其特点之一。
而说到自动配置，那自然离不开自动配置类，他即是功能的入口。
那Nacos有哪些自动配置类呢？
NacosServiceAutoConfiguration
这是Nacos服务器通信的基础设施，是整个 Nacos 集成的"连接管理中心"。
@Configuration(proxyBeanMethods = false
)
@ConditionalOnDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
public class NacosServiceAutoConfiguration {public NacosServiceAutoConfiguration() {}@Beanpublic NacosServiceManager nacosServiceManager() {return new NacosServiceManager();}// Spring 应用 → NacosServiceManager → Nacos SDK → Nacos 服务器}
NacosServiceManager 被多个 Nacos 相关组件使用:
服务发现组件:
NacosServiceDiscovery 使用它获取 NamingService 实例
NacosRegistration 使用它进行服务注册
配置中心组件:
NacosConfigManager 使用它获取 ConfigService 实例
配置刷新机制依赖它提供的服务对象
延迟初始化: NacosServiceManager 不会在创建时立即连接 Nacos 服务器，而是采用延迟初始化策略
按需创建服务对象:
当系统需要 NamingService (服务发现) 时，按需创建并缓存
当系统需要 ConfigService (配置中心) 时，按需创建并缓存
服务对象缓存机制:
基于属性（如命名空间、分组）创建缓存键
相同配置的服务请求复用同一个服务对象实例
避免重复创建连接，优化资源使用
生命周期管理:
与 Spring 容器生命周期绑定
在应用关闭时释放资源、关闭连接
NacosDiscoveryAutoConfiguration
这是Nacos的服务发现自动配置类，主要有如下功能
- 自动装配 Nacos 服务发现组件
- 初始化服务发现相关的基础设施 Bean
- 使应用能够与 Nacos 服务器进行服务注册与发现交互
@Configuration(proxyBeanMethods = false
)
@ConditionalOnDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
public class NacosDiscoveryAutoConfiguration {public NacosDiscoveryAutoConfiguration() {}@Bean@ConditionalOnMissingBeanpublic NacosDiscoveryProperties nacosProperties() {return new NacosDiscoveryProperties();}@Bean@ConditionalOnMissingBean // 需要传入NacosServiceManager ，通过其进行服务发现public NacosServiceDiscovery nacosServiceDiscovery(NacosDiscoveryProperties discoveryProperties, NacosServiceManager nacosServiceManager) { return new NacosServiceDiscovery(discoveryProperties, nacosServiceManager);}
}NacosServiceRegistryAutoConfiguration
上面两个，一个是提供操作服务的Service，一个是提供服务发现的功能，那这个就是提供自动注册的功能，其自动配置类如下：
@Configuration(proxyBeanMethods = false
)
@EnableConfigurationProperties
@ConditionalOnNacosDiscoveryEnabled // 自定义Condition注解，具体参考自动配置相关知识
@ConditionalOnProperty(value = {"spring.cloud.service-registry.auto-registration.enabled"},matchIfMissing = true
)
// 用于控制自动配置顺序
@AutoConfigureAfter({AutoServiceRegistrationConfiguration.class, AutoServiceRegistrationAutoConfiguration.class, NacosDiscoveryAutoConfiguration.class})
public class NacosServiceRegistryAutoConfiguration {public NacosServiceRegistryAutoConfiguration() {}@Bean // 用于提供注册功能的Service，其调用NacosServiceManager 进行实现 父类为 ServiceRegistry<R>public NacosServiceRegistry nacosServiceRegistry(NacosServiceManager nacosServiceManager, NacosDiscoveryProperties nacosDiscoveryProperties) {return new NacosServiceRegistry(nacosServiceManager, nacosDiscoveryProperties);}@Bean // 承载服务注册所需的实例信息，是注册数据的容器@ConditionalOnBean({AutoServiceRegistrationProperties.class})public NacosRegistration nacosRegistration(ObjectProvider<List<NacosRegistrationCustomizer>> registrationCustomizers, NacosDiscoveryProperties nacosDiscoveryProperties, ApplicationContext context) {return new NacosRegistration((List)registrationCustomizers.getIfAvailable(), nacosDiscoveryProperties, context);}@Bean // 自动服务注册的触发器，监听事件并执行注册@ConditionalOnBean({AutoServiceRegistrationProperties.class})public NacosAutoServiceRegistration nacosAutoServiceRegistration(NacosServiceRegistry registry, AutoServiceRegistrationProperties autoServiceRegistrationProperties, NacosRegistration registration) {return new NacosAutoServiceRegistration(registry, autoServiceRegistrationProperties, registration);}
}自动注册剖析
在上述第三个自动配置生效后，会返回一个 new NacosAutoServiceRegistration(registry, autoServiceRegistrationProperties, registration);
分析其继承关系。
可以发现其关系图中，有 ApplicationListener< WebServerInitializedEvent > 这个类，其作用是会监听对应事件，而这个事件就是WebServerInitializedEvent 代表嵌入式 Web 服务器已完成初始化并启动的通知机制。
public void onApplicationEvent(WebServerInitializedEvent event) {ApplicationContext context = event.getApplicationContext();if (!(context instanceof ConfigurableWebServerApplicationContext) || !"management".equals(((ConfigurableWebServerApplicationContext)context).getServerNamespace())) {this.port.compareAndSet(0, event.getWebServer().getPort());this.start(); // start方法}}
==》 start 方法
public void start() {if (!this.isEnabled()) {if (logger.isDebugEnabled()) {logger.debug("Discovery Lifecycle disabled. Not starting");}} else {if (!this.running.get()) {this.context.publishEvent(new InstancePreRegisteredEvent(this, this.getRegistration()));this.registrationLifecycles.forEach((registrationLifecycle) -> {registrationLifecycle.postProcessBeforeStartRegister(this.getRegistration());});this.register(); // 进行注册this.registrationLifecycles.forEach((registrationLifecycle) -> {registrationLifecycle.postProcessAfterStartRegister(this.getRegistration());});if (this.shouldRegisterManagement()) {this.registrationManagementLifecycles.forEach((registrationManagementLifecycle) -> {registrationManagementLifecycle.postProcessBeforeStartRegisterManagement(this.getManagementRegistration());});this.registerManagement();this.registrationManagementLifecycles.forEach((registrationManagementLifecycle) -> {registrationManagementLifecycle.postProcessAfterStartRegisterManagement(this.getManagementRegistration());});}this.context.publishEvent(new InstanceRegisteredEvent(this, this.getConfiguration()));this.running.compareAndSet(false, true);}}}
register方法
private final ServiceRegistry<R> serviceRegistry;
......
protected void register() {if (!this.registration.getNacosDiscoveryProperties().isRegisterEnabled()) {log.debug("Registration disabled.");} else {if (this.registration.getPort() < 0) {this.registration.setPort(this.getPort().get());}super.register();}}
// ==> super.register()
protected void register() {this.serviceRegistry.register(this.getRegistration()); // NacosRegistration}
serviceRegistry.register
public void register(Registration registration) {if (StringUtils.isEmpty(registration.getServiceId())) {log.warn("No service to register for nacos client...");} else {NamingService namingService = this.namingService();String serviceId = registration.getServiceId();String group = this.nacosDiscoveryProperties.getGroup();Instance instance = this.getNacosInstanceFromRegistration(registration);try {namingService.registerInstance(serviceId, group, instance); // 进行注册log.info("nacos registry, {} {} {}:{} register finished", new Object[]{group, serviceId, instance.getIp(), instance.getPort()});} catch (Exception var7) {Exception e = var7;if (this.nacosDiscoveryProperties.isFailFast()) {log.error("nacos registry, {} register failed...{},", new Object[]{serviceId, registration.toString(), e});ReflectionUtils.rethrowRuntimeException(e);} else {log.warn("Failfast is false. {} register failed...{},", new Object[]{serviceId, registration.toString(), e});}}}}
namingService.registerInstance
public void registerInstance(String serviceName, String groupName, Instance instance) throws NacosException {NamingUtils.checkInstanceIsLegal(instance);this.checkAndStripGroupNamePrefix(instance, groupName);this.clientProxy.registerService(serviceName, groupName, instance); // 通过代理去获取对应的注册服务}
clientProxy.registerService
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {this.getExecuteClientProxy(instance).registerService(serviceName, groupName, instance);}
getExecuteClientProxy
private NamingClientProxy getExecuteClientProxy(Instance instance) {return (NamingClientProxy)(!instance.isEphemeral() && !this.grpcClientProxy.isAbilitySupportedByServer(AbilityKey.SERVER_SUPPORT_PERSISTENT_INSTANCE_BY_GRPC) ? this.httpClientProxy : this.grpcClientProxy);}
是否临时服务判断
Nacos 提供两种注册方式，一种是临时，会进行心跳检测，如果心跳检测不超过，或者超时，就会被任务不健康实例，会对其进行下线，其次会将其加入一个队列中，去检测是否健康，如果不健康，那就移除。
一种是永久注册，下面详细介绍
临时实例 (Ephemeral = true)
-
生命周期特点：
- 基于心跳维持，客户端需要定期发送心跳包
- 如果一定时间内未收到心跳，Nacos会自动将实例标记为不健康，并最终移除
-
适用场景：
- 适合大多数微服务场景，特别是云原生环境
- 实例会随应用的启停自动注册和注销
-
数据存储：
- 存储在内存中，提供更高的性能
- 在Nacos服务器重启时数据会丢失
持久化实例 (Ephemeral = false)
-
生命周期特点：
- 实例信息持久化到磁盘
- 不依赖心跳维持，即使客户端宕机实例也不会被自动移除
-
适用场景：
- 适合那些需要保持稳定注册状态的场景
- 如某些关键基础设施服务，需要手动管理其上下线
-
数据存储：
- 数据持久化到磁盘数据库中
- Nacos重启后数据仍然存在
HttpClient.registerService
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {LogUtils.NAMING_LOGGER.info("[REGISTER-SERVICE] {} registering service {} with instance: {}", new Object[]{this.namespaceId, serviceName, instance});String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);if (instance.isEphemeral()) {throw new UnsupportedOperationException("Do not support register ephemeral instances by HTTP, please use gRPC replaced.");} else {Map<String, String> params = new HashMap(32);params.put("namespaceId", this.namespaceId);params.put("serviceName", groupedServiceName);params.put("groupName", groupName);params.put("clusterName", instance.getClusterName());params.put("ip", instance.getIp());params.put("port", String.valueOf(instance.getPort()));params.put("weight", String.valueOf(instance.getWeight()));params.put("enable", String.valueOf(instance.isEnabled()));params.put("healthy", String.valueOf(instance.isHealthy()));params.put("ephemeral", String.valueOf(instance.isEphemeral()));params.put("metadata", JacksonUtils.toJson(instance.getMetadata()));this.reqApi(UtilAndComs.nacosUrlInstance, params, "POST");}}
Grpc.registerService
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {LogUtils.NAMING_LOGGER.info("[REGISTER-SERVICE] {} registering service {} with instance {}", new Object[]{this.namespaceId, serviceName, instance});if (instance.isEphemeral()) {this.registerServiceForEphemeral(serviceName, groupName, instance);} else {this.doRegisterServiceForPersistent(serviceName, groupName, instance);}}
自上，自动注册服务就到此为止