深度剖析Spring Cloud Alibaba系列——如何兼容Nacos

//①省略大部分代码的35岁的程序员
public class NacosRegistration implements Registration, ServiceInstance {
    ...
    @PostConstruct
    public void init() {
        //②加载服务中，通过属性文件自定义的元数据，并Push到Nacos注册中心，这样在Nacos控制台就能看到开发人员自定义的元数据，这个功能真的非常重要
        Map<String, String> metadata = nacosDiscoveryProperties.getMetadata();
        //③读取服务中，通过代码硬编码的元数据，并Push到Nacos注册中心
        customize(registrationCustomizers, this);
    }
     //④执行加载元数据的具体逻辑
    private static void customize(
            List<NacosRegistrationCustomizer> registrationCustomizers,
            NacosRegistration registration) {
        //⑤其实这里有一个基于Spring Boot和面向接口的设计模式，非常方便大家在业务中做代码扩展，特别是复杂业务设计的场景，读者可以自己先体会。
        if (registrationCustomizers != null) {
            for (NacosRegistrationCustomizer customizer : registrationCustomizers) {
                customizer.customize(registration);
            }
        }
    }
    ...
}

public class NacosAutoServiceRegistration
        extends AbstractAutoServiceRegistration<Registration> {
    private NacosRegistration registration;
    //①好吧，Spring cloud Alibaba重写了Spring Cloud的注册方法register()
    @Override
    protected void register() {
        //②如果开启了自动注册，则调用Spring Cloud的注册方法，开启服务Spring Cloud的服务注册
        if (!this.registration.getNacosDiscoveryProperties().isRegisterEnabled()) {
            log.debug("Registration disabled.");
            return;
        }
        if (this.registration.getPort() < 0) {
            this.registration.setPort(getPort().get());
        }
        super.register();
    }
    ...
}

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties
@ConditionalOnNacosDiscoveryEnabled
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
        matchIfMissing = true)
@AutoConfigureAfter({ AutoServiceRegistrationConfiguration.class,
        AutoServiceRegistrationAutoConfiguration.class,
        NacosDiscoveryAutoConfiguration.class })
public class NacosServiceRegistryAutoConfiguration {
    //没错，它就是在NacosServiceRegistryAutoConfiguration 类中初始化的，但是这个Bean的初始化是没有靠条件注解来控制，个人感觉这里就应该加一个，读者可以自己尝试下，引入Spring Cloud Alibaba的包，但是不加注解@EnableDiscoveryClient，服务是会报错的。
    @Bean
    public NacosServiceRegistry nacosServiceRegistry(
            NacosDiscoveryProperties nacosDiscoveryProperties) {
        return new NacosServiceRegistry(nacosDiscoveryProperties);
    }
    ...
}

public class NacosServiceRegistry implements ServiceRegistry<Registration> {       
    //①NacosServiceManager 是Spring Cloud Alibaba对Nacos Client的二次封装
    @Autowired
    private NacosServiceManager nacosServiceManager;
    //②好吧，看到NamingService 类是不是很兴奋，没错，用它就是来注册服务的
    @Override
    public void register(Registration registration) {
       NamingService namingService = namingService();
       Instance instance = getNacosInstanceFromRegistration(registration);
       namingService.registerInstance(serviceId, group, instance);
       ...
    }

    @Override
     //③好吧，看到NamingService 类是不是很兴奋，没错，用它就是来取消注册服务的
public void deregister(Registration registration) {
        NamingService namingService = namingService();
        namingService.deregisterInstance(serviceId, group, registration.getHost(),
                    registration.getPort(), nacosDiscoveryProperties.getClusterName());
      ...
    }
    ...
}