@EnableDiscoveryClient与Nacos自动注册

 

前一阵看到有篇博客说cloud从Edgware版本开始,可以不加@EnableDiscoveryClient注解,只要配置好注册中心的相关配置即可自动开启服务注册功能,比较好奇其中的原理,研究了一番特意记录下来

 

先看一下@EnableDiscoveryClient注解,只有一个属性:autoRegister, 默认为true

@SpringBootApplication@EnableDiscoveryClient(autoRegister = true)public class NacosApplication {  public static void main(String[] args) {  SpringApplication.run(NacosApplication.class, args); } }

　　

内部信息(代码里只保留了重点)

@Import(EnableDiscoveryClientImportSelector.class)public @interface EnableDiscoveryClient {	boolean autoRegister() default true;}

　　

EnableDiscoveryClientImportSelector

@Overridepublic String[] selectImports(AnnotationMetadata metadata) { String[] imports = super.selectImports(metadata); AnnotationAttributes attributes = AnnotationAttributes.fromMap(  metadata.getAnnotationAttributes(getAnnotationClass().getName(), true));	//获取@EnableDiscoveryClient的autoRegister属性 boolean autoRegister = attributes.getBoolean("autoRegister");	//开启自动注册的话,将AutoServiceRegistrationConfiguration类的全限定名返回,会被spring加载到bean容器 if (autoRegister) {  List<String> importsList = new ArrayList<>(Arrays.asList(imports));  importsList.add(   "org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationConfiguration");  imports = importsList.toArray(new String[0]); } //关闭自动注册的话,将***.auto-registration.enabled设置为false,放入环境属性中(其他地方会用到) else {  Environment env = getEnvironment();  if (ConfigurableEnvironment.class.isInstance(env)) {   ConfigurableEnvironment configEnv = (ConfigurableEnvironment) env;   LinkedHashMap<String, Object> map = new LinkedHashMap<>();   map.put("spring.cloud.service-registry.auto-registration.enabled", false);   MapPropertySource propertySource = new MapPropertySource(    "springCloudDiscoveryClient", map);   configEnv.getPropertySources().addLast(propertySource);  } } return imports;}

　　

AutoServiceRegistrationConfiguration

//当**.registration.enabled属性为true时,此配置类会被加载//spring-cloud-commons.jar包内的spring-configuration-metadata.json定义了此属性默认为true//即: 不配置@EnableDiscoveryClient或者配置@EnableDiscoveryClient设置autoRegister为true时//AutoServiceRegistrationConfiguration会被加载,当@EnableDiscoveryClient的autoRegister//为false时,此配置类不会被加载@Configuration(proxyBeanMethods = false)@EnableConfigurationProperties(AutoServiceRegistrationProperties.class)@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",		matchIfMissing = true)public class AutoServiceRegistrationConfiguration {}

　　

AutoServiceRegistrationConfiguration是实现自动注册的入口,具体的逻辑在由注册中心实现(如Nacos\Eureka...)

spring: application: name: nacosTest cloud: nacos:  discovery:  enabled: true(默认为true,可以不配置)  server-addr: 192.168.1.10  port: 8848  username: nacos  password: nacos

　　

Nacos实现逻辑

spring-cloud-starter-alibaba-nacos-discovery.jar/META-INF/spring.factories:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryAutoConfiguration,\ com.alibaba.cloud.nacos.ribbon.RibbonNacosAutoConfiguration,\ com.alibaba.cloud.nacos.endpoint.NacosDiscoveryEndpointAutoConfiguration,\ com.alibaba.cloud.nacos.registry.NacosServiceRegistryAutoConfiguration,\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.reactive.NacosReactiveDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.configclient.NacosConfigServerAutoConfiguration,\ com.alibaba.cloud.nacos.NacosServiceAutoConfigurationorg.springframework.cloud.bootstrap.BootstrapConfiguration=\ com.alibaba.cloud.nacos.discovery.configclient.NacosDiscoveryClientConfigServiceBootstrapConfiguration

　　

打开NacosServiceRegistryAutoConfiguration.java, 内部实现了服务自动注册逻辑

@Configuration(proxyBeanMethods = false)@EnableConfigurationProperties//确保spring.cloud.nacos.discovery.enabled为true(开启nacos的服务注册与发现功能)@ConditionalOnNacosDiscoveryEnabled//默认为true,只有开启了@EnableDiscoveryClient注解,并且配置autoRegister为false时,//此属性值才为false@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",		matchIfMissing = true)@AutoConfigureAfter({ AutoServiceRegistrationConfiguration.class,		AutoServiceRegistrationAutoConfiguration.class,		NacosDiscoveryAutoConfiguration.class })public class NacosServiceRegistryAutoConfiguration {	@Bean	public NacosServiceRegistry nacosServiceRegistry(			NacosDiscoveryProperties nacosDiscoveryProperties) {		return new NacosServiceRegistry(nacosDiscoveryProperties);	}	@Bean	@ConditionalOnBean(AutoServiceRegistrationProperties.class)	public NacosRegistration nacosRegistration(			ObjectProvider<List<NacosRegistrationCustomizer>> registrationCustomizers,			NacosDiscoveryProperties nacosDiscoveryProperties,			ApplicationContext context) {		return new Nac......
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前一阵看到有篇博客说cloud从Edgware版本开始,可以不加@EnableDiscoveryClient注解,只要配置好注册中心的相关配置即可自动开启服务注册功能,比较好奇其中的原理,研究了一番特意记录下来先看一下@EnableDiscoveryClient注解,只有一个属性:autoRegister,默认为true@SpringBootApplication@EnableDiscoveryC
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