@EnableDiscoveryClient与Nacos的服务注册与拉取 |
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@EnableDiscoveryClient与Nacos的服务注册与拉取
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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 环境: SpringBoot: 2.3.5 SpringCloud: Hoxton.SR8 SpringCloudAlibaba: 2.2.3 配置信息: @SpringBootApplication //autoRegiste属性值默认为true可以不配置此属性 @EnableDiscoveryClient(autoRegister = true) public class NacosApplication { public static void main(String[] args) { SpringApplication.run(NacosApplication.class, args); } } spring: application: name: nacosTest cloud: nacos: discovery: enabled: true(默认为true,可以不配置此属性) server-addr: 192.168.1.10:8848 username: nacos password: nacos 配置的作用:nacos.discovery.enabled: 开启服务的注册与发现功能;
注册成功后可以在nacos的web端界面看到服务的相关信息
@EnableDiscoveryClient(autoRegister = true); 开启服务自动注册功能,项目启动后能在nacos的web端界面看到服务的相关信息,并且具备拉取服务信息的功能(前提是nacos.discovery.enabled不为false) @EnableDiscoveryClient(autoRegister = false); 关闭服务自动注册功能, 项目启动后nacos的web端界面没有此项目的信息,但是依然具备拉取服务信息的功能(前提是nacos.discovery.enabled不为false) 实现逻辑: @EnableDiscoveryClient打开@EnableDiscoveryClient注解(代码里只保留了重点) @Import(EnableDiscoveryClientImportSelector.class) public @interface EnableDiscoveryClient { boolean autoRegister() default true; }进入EnableDiscoveryClientImportSelector类 @Override public 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 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 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; }既然开启自动注册服务会返回一个叫AutoServiceRegistrationConfiguration的类,那就打开看一下: 此类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...) //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设置autoRegister //属性为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 { }到现在似乎还没发现太多有用的信息,那继续看Nacos的源码 Nacos:找到nacos的spring.factories文件,这是配置自动配置类的地方,文件路径: spring-cloud-starter-alibaba-nacos-discovery.jar/META-INF/spring.factories 文件信息: 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.NacosServiceAutoConfiguration org.springframework.cloud.bootstrap.BootstrapConfiguration=\ com.alibaba.cloud.nacos.discovery.configclient.NacosDiscoveryClientConfigServiceBootstrapConfiguration既然有BootstrapConfiguration,那就先看最后一行的NacosDiscoveryClientConfigServiceBootstrapConfiguration //删减了部分代码,便于阅读 @ImportAutoConfiguration({NacosDiscoveryClientConfiguration.class}) public class NacosDiscoveryClientConfigServiceBootstrapConfiguration { }继续进入NacosDiscoveryClientConfiguration //删减了部分代码,便于阅读 //spring.cloud.nacos.discovery.enabled=true时,此配置类才会加载 @ConditionalOnNacosDiscoveryEnabled @AutoConfigureAfter(NacosDiscoveryAutoConfiguration.class) public class NacosDiscoveryClientConfiguration { @Bean public DiscoveryClient nacosDiscoveryClient(NacosServiceDiscovery nacosServiceDiscovery) { return new NacosDiscoveryClient(nacosServiceDiscovery); } }此配置类注入了一个bean: NacosDiscoveryClient, 这个类实现了DiscoveryClient接口, 我们上边的测试用例 discoveryClient.getInstances("服务名称"), 调用的getInstances方法,实际上就是调用了Nacos官方提供的NacosDiscoveryClient重写的getInstances方法, 至此,Nacos的的服务拉取搞明白了: 无论是否配置@EnableDiscoveryClient,只要spring.cloud.nacos.discovery.enabled不设置为false,服务就具有拉取注册中心信息的功能 那服务注册功能呢? 返回spring.factories打开第五行的类: NacosServiceRegistryAutoConfiguration 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,使用@EnableDiscoveryClient注解配置autoRegister为false时,次属性值为false //即: 此类不被加载,即: 服务不具备自动注册功能 @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 registrationCustomizers, NacosDiscoveryProperties nacosDiscoveryProperties, ApplicationContext context) { return new NacosRegistration(registrationCustomizers.getIfAvailable(), nacosDiscoveryProperties, context); } @Bean @ConditionalOnBean(AutoServiceRegistrationProperties.class) public NacosAutoServiceRegistration nacosAutoServiceRegistration( NacosServiceRegistry registry, AutoServiceRegistrationProperties autoServiceRegistrationProperties, NacosRegistration registration) { return new NacosAutoServiceRegistration(registry, autoServiceRegistrationProperties, registration); } } 实验结论: 配置 效果 不配置@EnableDiscoveryClient,不配置nacos.discovery.enable 具有服务自动注册功能,具有拉取服务信息功能 不配置@EnableDiscoveryClient,配置nacos.discovery.enable=false 服务注册与拉取服务信息功能都不具备 配置@EnableDiscoveryClient(autoRegister=false),配置nacos.discovery.enable=true 不具有服务注册功能,具有拉取服务信息功能 配置@EnableDiscoveryClient(autoRegister=false),配置nacos.discovery.enable=false 服务注册与拉取服务信息功能都不具备 最后:才疏学浅,难免有疏漏或者错误的地方,希望各位不吝指教 |
同时,具备拉取服务信息的功能, discoveryClient.getInstances()方法可以返回服务的详细配置信息【本文地址】
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