Spring Cloud Netflix Eureka client源码分析

1.client端

EurekaClient提供三个功能：

EurekaClient API contracts are:
* - provide the ability to get InstanceInfo(s) (in various different ways)
* - provide the ability to get data about the local Client (known regions, own AZ etc)
* - provide the ability to register and access the healthcheck handler for the client

使用@EnableEurekaClient起效，其定义如下：

/**
 * Convenience annotation for clients to enable Eureka discovery configuration
 * (specifically). Use this (optionally) in case you want discovery and know for sure that
 * it is Eureka you want. All it does is turn on discovery and let the autoconfiguration
 * find the eureka classes if they are available (i.e. you need Eureka on the classpath as
 * well).
 *
 * @author Dave Syer
 * @author Spencer Gibb
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@EnableDiscoveryClient
public @interface EnableEurekaClient {

}

注册

/**
 * Annotation to enable a DiscoveryClient implementation.
 * @author Spencer Gibb
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(EnableDiscoveryClientImportSelector.class)
public @interface EnableDiscoveryClient {

    /**
     * If true, the ServiceRegistry will automatically register the local server.
     */
    boolean autoRegister() default true;
}

EnableDiscoveryClientImportSelector继承自SpringFactoryImportSelector，在容器启动时触发,前文已经有介绍执行路径：

在其父类org.springframework.cloud.commons.util.SpringFactoryImportSelector
的String[] selectImports(AnnotationMetadata metadata)方法中正是根据这个标记类判定是否加载如下定义的类。

@Override
    public String[] selectImports(AnnotationMetadata metadata) {
        if (!isEnabled()) {
            return new String[0];
        }
        AnnotationAttributes attributes = AnnotationAttributes.fromMap(
                metadata.getAnnotationAttributes(this.annotationClass.getName(), true));

        Assert.notNull(attributes, "No " + getSimpleName() + " attributes found. Is "
                + metadata.getClassName() + " annotated with @" + getSimpleName() + "?");

        // Find all possible auto configuration classes, filtering duplicates
        List<String> factories = new ArrayList<>(new LinkedHashSet<>(SpringFactoriesLoader
                .loadFactoryNames(this.annotationClass, this.beanClassLoader)));

        if (factories.isEmpty() && !hasDefaultFactory()) {
            throw new IllegalStateException("Annotation @" + getSimpleName()
                    + " found, but there are no implementations. Did you forget to include a starter?");
        }

        if (factories.size() > 1) {
            // there should only ever be one DiscoveryClient, but there might be more than
            // one factory
            log.warn("More than one implementation " + "of @" + getSimpleName()
                    + " (now relying on @Conditionals to pick one): " + factories);
        }

        return factories.toArray(new String[factories.size()]);
    }

SpringFactoriesLoader调用loadFactoryNames其实加载META-INF/spring.factories下的class。

spring-cloud-netflix-eureka-client\src\main\resources\META-INF\spring.factories中配置：

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.netflix.eureka.config.EurekaClientConfigServerAutoConfiguration,\
org.springframework.cloud.netflix.eureka.config.EurekaDiscoveryClientConfigServiceAutoConfiguration,\
org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration,\
org.springframework.cloud.netflix.ribbon.eureka.RibbonEurekaAutoConfiguration

org.springframework.cloud.bootstrap.BootstrapConfiguration=\
org.springframework.cloud.netflix.eureka.config.EurekaDiscoveryClientConfigServiceBootstrapConfiguration

org.springframework.cloud.client.discovery.EnableDiscoveryClient=\
org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration

1.1 EurekaClientAutoConfiguration

1.1.1 定义HasFeatures Bean

    @Bean
    public HasFeatures eurekaFeature() {
        return HasFeatures.namedFeature("Eureka Client", EurekaClient.class);
    }

1.1.2 定义EurekaClientConfigBean bean

    @Bean
    @ConditionalOnMissingBean(value = EurekaClientConfig.class, search = SearchStrategy.CURRENT)
    public EurekaClientConfigBean eurekaClientConfigBean() {
        EurekaClientConfigBean client = new EurekaClientConfigBean();
        if ("bootstrap".equals(this.env.getProperty("spring.config.name"))) {
            // We don't register during bootstrap by default, but there will be another
            // chance later.
            client.setRegisterWithEureka(false);
        }
        return client;
    }

1.1.3 定义EurekaInstanceConfigBean bean

@Bean
    @ConditionalOnMissingBean(value = EurekaInstanceConfig.class, search = SearchStrategy.CURRENT)
    public EurekaInstanceConfigBean eurekaInstanceConfigBean(InetUtils inetUtils) {
        EurekaInstanceConfigBean instance = new EurekaInstanceConfigBean(inetUtils);
        instance.setNonSecurePort(this.nonSecurePort);
        instance.setInstanceId(getDefaultInstanceId(this.env));

        if (this.managementPort != this.nonSecurePort && this.managementPort != 0) {
            if (StringUtils.hasText(this.hostname)) {
                instance.setHostname(this.hostname);
            }
            RelaxedPropertyResolver relaxedPropertyResolver = new RelaxedPropertyResolver(env, "eureka.instance.");
            String statusPageUrlPath = relaxedPropertyResolver.getProperty("statusPageUrlPath");
            String healthCheckUrlPath = relaxedPropertyResolver.getProperty("healthCheckUrlPath");
            if (StringUtils.hasText(statusPageUrlPath)) {
                instance.setStatusPageUrlPath(statusPageUrlPath);
            }
            if (StringUtils.hasText(healthCheckUrlPath)) {
                instance.setHealthCheckUrlPath(healthCheckUrlPath);
            }
            String scheme = instance.getSecurePortEnabled() ? "https" : "http";
            instance.setStatusPageUrl(scheme + "://" + instance.getHostname() + ":"
                    + this.managementPort + instance.getStatusPageUrlPath());
            instance.setHealthCheckUrl(scheme + "://" + instance.getHostname() + ":"
                    + this.managementPort + instance.getHealthCheckUrlPath());
        }
        return instance;
    }

1.1.4 定义DiscoveryClient bean

    @Bean
    public DiscoveryClient discoveryClient(EurekaInstanceConfig config,
            EurekaClient client) {
        return new EurekaDiscoveryClient(config, client);
    }

1.1.5 定义EurekaServiceRegistry bean

    @Bean
    public EurekaServiceRegistry eurekaServiceRegistry() {
        return new EurekaServiceRegistry();
    }

1.1.6 定义EurekaRegistration bean

    @Bean
    @ConditionalOnBean(AutoServiceRegistrationProperties.class)
    @ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
    public EurekaRegistration eurekaRegistration(EurekaClient eurekaClient, CloudEurekaInstanceConfig instanceConfig, ApplicationInfoManager applicationInfoManager) {
        return EurekaRegistration.builder(instanceConfig)
                .with(applicationInfoManager)
                .with(eurekaClient)
                .with(healthCheckHandler)
                .build();
    }

1.1.7 定义EurekaAutoServiceRegistration bean

    @Bean
    @ConditionalOnBean(AutoServiceRegistrationProperties.class)
    @ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
    public EurekaAutoServiceRegistration eurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry registry, EurekaRegistration registration) {
        return new EurekaAutoServiceRegistration(context, registry, registration);
    }

1.2 EurekaClientConfiguration
1.2.1  定义EurekaClient bean

        @Bean(destroyMethod = "shutdown")
        @ConditionalOnMissingBean(value = EurekaClient.class, search = SearchStrategy.CURRENT)
        public EurekaClient eurekaClient(ApplicationInfoManager manager,
                EurekaClientConfig config) {
            return new CloudEurekaClient(manager, config, this.optionalArgs,
                    this.context);
        }

1.2.2 定义ApplicationInfoManager bean

        @Bean
        @ConditionalOnMissingBean(value = ApplicationInfoManager.class, search = SearchStrategy.CURRENT)
        public ApplicationInfoManager eurekaApplicationInfoManager(
                EurekaInstanceConfig config) {
            InstanceInfo instanceInfo = new InstanceInfoFactory().create(config);
            return new ApplicationInfoManager(config, instanceInfo);
        }

1.3 RefreshableEurekaClientConfiguration

1.3.1 定义EurekaClient bean

        @Bean(destroyMethod = "shutdown")
        @ConditionalOnMissingBean(value = EurekaClient.class, search = SearchStrategy.CURRENT)
        @org.springframework.cloud.context.config.annotation.RefreshScope
        @Lazy
        public EurekaClient eurekaClient(ApplicationInfoManager manager,
                EurekaClientConfig config, EurekaInstanceConfig instance) {
            manager.getInfo(); // force initialization
            return new CloudEurekaClient(manager, config, this.optionalArgs,
                    this.context);
        }

1.3.2 定义ApplicationInfoManager

        @Bean
        @ConditionalOnMissingBean(value = ApplicationInfoManager.class, search = SearchStrategy.CURRENT)
        @org.springframework.cloud.context.config.annotation.RefreshScope
        @Lazy
        public ApplicationInfoManager eurekaApplicationInfoManager(
                EurekaInstanceConfig config) {
            InstanceInfo instanceInfo = new InstanceInfoFactory().create(config);
            return new ApplicationInfoManager(config, instanceInfo);
        }

参考文献：
http://blog.csdn.net/neosmith/article/details/53131023