3 nacos 服务注册之 SpringCloud 集成 nacos
服务注册的功能主要体现在：
ServiceRegistry 是 Spring Cloud 提供的服务注册的标准。集成到 Spring Cloud 中实现服务注册的组件，都会实现该接口。
ServiceRegistry 接口
public interface ServiceRegistry<R extends Registration> {
/** * Registers the registration. A registration typically has information about an * instance, such as its hostname and port. * @param registration registration meta data */ void register(R registration);
/** * Deregisters the registration. * @param registration registration meta data */ void deregister(R registration);
/** * Closes the ServiceRegistry. This is a lifecycle method. */ void close();
/** * Sets the status of the registration. The status values are determined by the * individual implementations. * @param registration The registration to update. * @param status The status to set. * @see org.springframework.cloud.client.serviceregistry.endpoint.ServiceRegistryEndpoint */ void setStatus(R registration, String status);
/** * Gets the status of a particular registration. * @param registration The registration to query. * @param <T> The type of the status. * @return The status of the registration. * @see org.springframework.cloud.client.serviceregistry.endpoint.ServiceRegistryEndpoint */ <T> T getStatus(R registration);
}
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这个接口定义的方法有 register()注册方法，deregister()不进行注册的方法，close()关闭注册的方法。
NacosServiceRegistry 实现该接口
SpringCloud 集成 nacos
自动装配
spring-cloud-commons 包的 META-INF/spring.factories 自动装配：
# AutoConfigurationorg.springframework.boot.autoconfigure.EnableAutoConfiguration=\org.springframework.cloud.client.CommonsClientAutoConfiguration,\org.springframework.cloud.client.discovery.composite.CompositeDiscoveryClientAutoConfiguration,\org.springframework.cloud.client.discovery.noop.NoopDiscoveryClientAutoConfiguration,\org.springframework.cloud.client.discovery.simple.SimpleDiscoveryClientAutoConfiguration,\org.springframework.cloud.client.hypermedia.CloudHypermediaAutoConfiguration,\org.springframework.cloud.client.loadbalancer.AsyncLoadBalancerAutoConfiguration,\org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration,\org.springframework.cloud.client.loadbalancer.reactive.ReactiveLoadBalancerAutoConfiguration,\org.springframework.cloud.client.serviceregistry.ServiceRegistryAutoConfiguration,\org.springframework.cloud.commons.httpclient.HttpClientConfiguration,\org.springframework.cloud.commons.util.UtilAutoConfiguration,\org.springframework.cloud.configuration.CompatibilityVerifierAutoConfiguration,\org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration
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EnableAutoConfiguration 中定义了自动配置的类 AutoServiceRegistrationAutoConfiguration，AutoServiceRegistrationAutoConfiguration 是服务注册相关的配置类，我们看一下这个类做了什么
AutoServiceRegistrationAutoConfiguration 类
@Configuration(proxyBeanMethods = false)@Import(AutoServiceRegistrationConfiguration.class)@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)public class AutoServiceRegistrationAutoConfiguration {
@Autowired(required = false) private AutoServiceRegistration autoServiceRegistration;
@Autowired private AutoServiceRegistrationProperties properties;
@PostConstruct protected void init() { if (this.autoServiceRegistration == null && this.properties.isFailFast()) { throw new IllegalStateException("Auto Service Registration has " + "been requested, but there is no AutoServiceRegistration bean"); } }
}
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AutoServiceRegistrationAutoConfiguration 类中注入了 AutoServiceRegistration，AutoServiceRegistration 是个接口，而 AbstractAutoServiceRegistration 实现了这个接口，而 NacosAutoServiceRegistration 继承了 AbstractAutoServiceRegistrationAbstractAutoServiceRegistration 同时实现了 ApplicationListener 接口：
ApplicationListener 接口
ApplicationListener 接口的定义如下
@FunctionalInterfacepublic interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
/** * Handle an application event. * @param event the event to respond to */ void onApplicationEvent(E event);
}
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接口中方法的作用是监听某个特定事件，
AbstractAutoServiceRegistration 实现了这个接口
AbstractAutoServiceRegistration 类
AbstractAutoServiceRegistration 类
@Override@SuppressWarnings("deprecation")public void onApplicationEvent(WebServerInitializedEvent event) { bind(event);}
@Deprecatedpublic 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()); this.start();}
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AbstractAutoServiceRegistration 监听 WebServerInitializedEvent 事件，调用 bind 方法 ，最终调用 NacosServiceRegistry 的 register 方法
总结
这就是 SpringCloud 是如何集成 nacos 的，说到底就是利用了 spring.factories 的自动装配机制，自动装配了 AutoServiceRegistrationAutoConfiguration 类，这个类中又注入了 AutoServiceRegistration 接口的实现类 NacosAutoServiceRegistration 的实例，NacosAutoServiceRegistration 的父类 AbstractAutoServiceRegistration 有监听方法，用来进行服务的启动注册。
总结一下：服务注册的功能主要体现在：
这就是 SpringCloud 集成 nacos 的部分，ServiceRegistry 是 Spring Cloud 提供的服务注册的标准。如果你有什么不懂的地方，或者我写错的地方，欢迎给我留言评论，我们一起学习一起进步，一起成就更好的自己，提升技术，服务业务，服务工作。我们一起努力，共同进步，我们下篇文章见，下篇文章我们将从这个 start()方法入手，分析一下 nacos 是怎么实现服务注册的
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