聊聊spring cloud netflix ribbon的eager load

序

本文主要研究一下spring cloud netflix ribbon的eager load

RibbonAutoConfiguration

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/RibbonAutoConfiguration.java

@Configuration
@Conditional(RibbonAutoConfiguration.RibbonClassesConditions.class)
@RibbonClients
@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
@AutoConfigureBefore({ LoadBalancerAutoConfiguration.class,
		AsyncLoadBalancerAutoConfiguration.class })
@EnableConfigurationProperties({ RibbonEagerLoadProperties.class,
		ServerIntrospectorProperties.class })
public class RibbonAutoConfiguration {

	@Autowired(required = false)
	private List<RibbonClientSpecification> configurations = new ArrayList<>();

	@Autowired
	private RibbonEagerLoadProperties ribbonEagerLoadProperties;

	@Bean
	public HasFeatures ribbonFeature() {
		return HasFeatures.namedFeature("Ribbon", Ribbon.class);
	}

	@Bean
	public SpringClientFactory springClientFactory() {
		SpringClientFactory factory = new SpringClientFactory();
		factory.setConfigurations(this.configurations);
		return factory;
	}

	@Bean
	@ConditionalOnMissingBean(LoadBalancerClient.class)
	public LoadBalancerClient loadBalancerClient() {
		return new RibbonLoadBalancerClient(springClientFactory());
	}

	@Bean
	@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
	@ConditionalOnMissingBean
	public LoadBalancedRetryFactory loadBalancedRetryPolicyFactory(
			final SpringClientFactory clientFactory) {
		return new RibbonLoadBalancedRetryFactory(clientFactory);
	}

	@Bean
	@ConditionalOnMissingBean
	public PropertiesFactory propertiesFactory() {
		return new PropertiesFactory();
	}

	@Bean
	@ConditionalOnProperty("ribbon.eager-load.enabled")
	public RibbonApplicationContextInitializer ribbonApplicationContextInitializer() {
		return new RibbonApplicationContextInitializer(springClientFactory(),
				ribbonEagerLoadProperties.getClients());
	}

	@Configuration
	@ConditionalOnClass(HttpRequest.class)
	@ConditionalOnRibbonRestClient
	protected static class RibbonClientHttpRequestFactoryConfiguration {

		@Autowired
		private SpringClientFactory springClientFactory;

		@Bean
		public RestTemplateCustomizer restTemplateCustomizer(
				final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {
			return restTemplate -> restTemplate
					.setRequestFactory(ribbonClientHttpRequestFactory);
		}

		@Bean
		public RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory() {
			return new RibbonClientHttpRequestFactory(this.springClientFactory);
		}

	}

	// TODO: support for autoconfiguring restemplate to use apache http client or okhttp

	@Target({ ElementType.TYPE, ElementType.METHOD })
	@Retention(RetentionPolicy.RUNTIME)
	@Documented
	@Conditional(OnRibbonRestClientCondition.class)
	@interface ConditionalOnRibbonRestClient {

	}

	private static class OnRibbonRestClientCondition extends AnyNestedCondition {

		OnRibbonRestClientCondition() {
			super(ConfigurationPhase.REGISTER_BEAN);
		}

		@Deprecated // remove in Edgware"
		@ConditionalOnProperty("ribbon.http.client.enabled")
		static class ZuulProperty {

		}

		@ConditionalOnProperty("ribbon.restclient.enabled")
		static class RibbonProperty {

		}

	}

	/**
	 * {@link AllNestedConditions} that checks that either multiple classes are present.
	 */
	static class RibbonClassesConditions extends AllNestedConditions {

		RibbonClassesConditions() {
			super(ConfigurationPhase.PARSE_CONFIGURATION);
		}

		@ConditionalOnClass(IClient.class)
		static class IClientPresent {

		}

		@ConditionalOnClass(RestTemplate.class)
		static class RestTemplatePresent {

		}

		@ConditionalOnClass(AsyncRestTemplate.class)
		static class AsyncRestTemplatePresent {

		}

		@ConditionalOnClass(Ribbon.class)
		static class RibbonPresent {

		}

	}

}

• RibbonAutoConfiguration启用了RibbonEagerLoadProperties、ServerIntrospectorProperties两个配置，这里主要是注册了SpringClientFactory，创建LoadBalancerClient、LoadBalancedRetryFactory、RibbonApplicationContextInitializer、RestTemplateCustomizer及RibbonClientHttpRequestFactory

RibbonApplicationContextInitializer

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/RibbonApplicationContextInitializer.java

public class RibbonApplicationContextInitializer
		implements ApplicationListener<ApplicationReadyEvent> {

	private final SpringClientFactory springClientFactory;

	// List of Ribbon client names
	private final List<String> clientNames;

	public RibbonApplicationContextInitializer(SpringClientFactory springClientFactory,
			List<String> clientNames) {
		this.springClientFactory = springClientFactory;
		this.clientNames = clientNames;
	}

	protected void initialize() {
		if (clientNames != null) {
			for (String clientName : clientNames) {
				this.springClientFactory.getContext(clientName);
			}
		}
	}

	@Override
	public void onApplicationEvent(ApplicationReadyEvent event) {
		initialize();
	}

}

• RibbonApplicationContextInitializer实现了ApplicationListener接口，其响应ApplicationReadyEvent事件执行initialize操作，这里主要是挨个对配置的clientNames执行springClientFactory.getContext(clientName)操作

SpringClientFactory

spring-cloud-netflix-ribbon-2.1.1.RELEASE-sources.jar!/org/springframework/cloud/netflix/ribbon/SpringClientFactory.java

public class SpringClientFactory extends NamedContextFactory<RibbonClientSpecification> {
	//......

	protected AnnotationConfigApplicationContext getContext(String name) {
		return super.getContext(name);
	}

	//......
}

• SpringClientFactory的getContext方法调用了父类NamedContextFactory的getContext

NamedContextFactory

spring-cloud-context-2.2.0.M1-sources.jar!/org/springframework/cloud/context/named/NamedContextFactory.java

public abstract class NamedContextFactory<C extends NamedContextFactory.Specification>
		implements DisposableBean, ApplicationContextAware {

	//......

	protected AnnotationConfigApplicationContext getContext(String name) {
		if (!this.contexts.containsKey(name)) {
			synchronized (this.contexts) {
				if (!this.contexts.containsKey(name)) {
					this.contexts.put(name, createContext(name));
				}
			}
		}
		return this.contexts.get(name);
	}

	protected AnnotationConfigApplicationContext createContext(String name) {
		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
		if (this.configurations.containsKey(name)) {
			for (Class<?> configuration : this.configurations.get(name)
					.getConfiguration()) {
				context.register(configuration);
			}
		}
		for (Map.Entry<String, C> entry : this.configurations.entrySet()) {
			if (entry.getKey().startsWith("default.")) {
				for (Class<?> configuration : entry.getValue().getConfiguration()) {
					context.register(configuration);
				}
			}
		}
		context.register(PropertyPlaceholderAutoConfiguration.class,
				this.defaultConfigType);
		context.getEnvironment().getPropertySources().addFirst(new MapPropertySource(
				this.propertySourceName,
				Collections.<String, Object>singletonMap(this.propertyName, name)));
		if (this.parent != null) {
			// Uses Environment from parent as well as beans
			context.setParent(this.parent);
			// jdk11 issue
			// https://github.com/spring-cloud/spring-cloud-netflix/issues/3101
			context.setClassLoader(this.parent.getClassLoader());
		}
		context.setDisplayName(generateDisplayName(name));
		context.refresh();
		return context;
	}

	//......
}		

• NamedContextFactory的getContext主要是返回或者创建AnnotationConfigApplicationContext

小结

• RibbonAutoConfiguration启用了RibbonEagerLoadProperties、ServerIntrospectorProperties两个配置，这里主要是注册了SpringClientFactory，创建LoadBalancerClient、LoadBalancedRetryFactory、RibbonApplicationContextInitializer、RestTemplateCustomizer及RibbonClientHttpRequestFactory
• RibbonApplicationContextInitializer实现了ApplicationListener接口，其响应ApplicationReadyEvent事件执行initialize操作，这里主要是挨个对配置的clientNames执行springClientFactory.getContext(clientName)操作
• SpringClientFactory的getContext方法调用了父类NamedContextFactory的getContext；NamedContextFactory的getContext主要是返回或者创建AnnotationConfigApplicationContext

doc

• RibbonClientConfiguration

来源：oschina

链接：https://my.oschina.net/u/2922256/blog/3071302