Spring Cloud @RefreshScope 原理及使用
@RefreshScope那些事
要说清楚RefreshScope,先要了解Scope
- Scope(org.springframework.beans.factory.config.Scope)是Spring 2.0开始就有的核心的概念
- RefreshScope(org.springframework.cloud.context.scope.refresh)是spring cloud提供的一种特殊的scope实现,用来实现配置、实例热加载。
- Scope -> GenericScope -> RefreshScope
Scope与ApplicationContext生命周期
AbstractBeanFactory#doGetBean创建Bean实例
protected <T> T doGetBean(...){ final RootBeanDefinition mbd = ... if (mbd.isSingleton()) { ... } else if (mbd.isPrototype()) ... } else { String scopeName = mbd.getScope(); final Scope scope = this.scopes.get(scopeName); Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {...}); ... } ... }
Singleton和Prototype是硬编码的,并不是Scope子类。 Scope实际上是自定义扩展的接口
Scope Bean实例交由Scope自己创建,例如SessionScope是从Session中获取实例的,ThreadScope是从ThreadLocal中获取的,而RefreshScope是在内建缓存中获取的。
@Scope 对象的实例化
@RefreshScope 是scopeName="refresh"的 @Scope
... @Scope("refresh") public @interface RefreshScope { ... }
@Scope 的注册 AnnotatedBeanDefinitionReader#registerBean
public void registerBean(...){ ... ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); abd.setScope(scopeMetadata.getScopeName()); ... definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); }
读取@Scope元数据, AnnotationScopeMetadataResolver#resolveScopeMetadata
public ScopeMetadata resolveScopeMetadata(BeanDefinition definition) { AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor( annDef.getMetadata(), Scope.class); if (attributes != null) { metadata.setScopeName(attributes.getString("value")); ScopedProxyMode proxyMode = attributes.getEnum("proxyMode"); if (proxyMode == null || proxyMode == ScopedProxyMode.DEFAULT) { proxyMode = this.defaultProxyMode; } metadata.setScopedProxyMode(proxyMode); } }
Scope实例对象通过ScopedProxyFactoryBean创建,其中通过AOP使其实现ScopedObject接口,这里不再展开
现在来说说RefreshScope是如何实现配置和实例刷新的
RefreshScope注册
RefreshAutoConfiguration#RefreshScopeConfiguration
@Component @ConditionalOnMissingBean(RefreshScope.class) protected static class RefreshScopeConfiguration implements BeanDefinitionRegistryPostProcessor{ ... registry.registerBeanDefinition("refreshScope", BeanDefinitionBuilder.genericBeanDefinition(RefreshScope.class) .setRole(BeanDefinition.ROLE_INFRASTRUCTURE) .getBeanDefinition()); ... }
RefreshScope extends GenericScope, 大部分逻辑在 GenericScope 中
GenericScope#postProcessBeanFactory 中向AbstractBeanFactory注册自己
public class GenericScope implements Scope, BeanFactoryPostProcessor...{ @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { beanFactory.registerScope(this.name/*refresh*/, this/*RefreshScope*/); ... } }
RefreshScope 刷新过程
入口在ContextRefresher#refresh
refresh() { Map<String, Object> before = ①extract( this.context.getEnvironment().getPropertySources()); ②addConfigFilesToEnvironment(); Set<String> keys = ④changes(before, ③extract(this.context.getEnvironment().getPropertySources())).keySet(); this.context.⑤publishEvent(new EnvironmentChangeEvent(keys)); this.scope.⑥refreshAll(); }
①提取标准参数(SYSTEM,JNDI,SERVLET)之外所有参数变量
②把原来的Environment里的参数放到一个新建的Spring Context容器下重新加载,完事之后关闭新容器
③提起更新过的参数(排除标准参数)
④比较出变更项
⑤发布环境变更事件,接收:EnvironmentChangeListener/LoggingRebinder
⑥RefreshScope用新的环境参数重新生成Bean
重新生成的过程很简单,清除refreshscope缓存幷销毁Bean,下次就会重新从BeanFactory获取一个新的实例(该实例使用新的配置)
RefreshScope#refreshAll
public void refreshAll() { <b>super.destroy();</b> this.context.publishEvent(new RefreshScopeRefreshedEvent()); } GenericScope#destroy public void destroy() { ... Collection<BeanLifecycleWrapper> wrappers = <b>this.cache.clear()</b>; for (BeanLifecycleWrapper wrapper : wrappers) { <b>wrapper.destroy();</b> } }
Spring Cloud Bus 如何触发 Refresh
BusAutoConfiguration#BusRefreshConfiguration 发布一个RefreshBusEndpoint
@Configuration @ConditionalOnClass({ Endpoint.class, RefreshScope.class }) protected static class BusRefreshConfiguration { @Configuration @ConditionalOnBean(ContextRefresher.class) @ConditionalOnProperty(value = "endpoints.spring.cloud.bus.refresh.enabled", matchIfMissing = true) protected static class BusRefreshEndpointConfiguration { @Bean public RefreshBusEndpoint refreshBusEndpoint(ApplicationContext context, BusProperties bus) { return new RefreshBusEndpoint(context, bus.getId()); } } }
RefreshBusEndpoint 会从http端口触发广播RefreshRemoteApplicationEvent事件
@Endpoint(id = "bus-refresh") public class RefreshBusEndpoint extends AbstractBusEndpoint { public void busRefresh() { publish(new RefreshRemoteApplicationEvent(this, getInstanceId(), null)); } }
BusAutoConfiguration#refreshListener 负责接收事件(所有配置bus的节点)
@Bean @ConditionalOnProperty(value = "spring.cloud.bus.refresh.enabled", matchIfMissing = true) @ConditionalOnBean(ContextRefresher.class) public RefreshListener refreshListener(ContextRefresher contextRefresher) { return new RefreshListener(contextRefresher); }
RefreshListener#onApplicationEvent 触发 ContextRefresher
public void onApplicationEvent(RefreshRemoteApplicationEvent event) { Set<String> keys = contextRefresher.refresh(); }
大部分需要更新的服务需要打上@RefreshScope, EurekaClient是如何配置更新的
EurekaClientAutoConfiguration#RefreshableEurekaClientConfiguration
@Configuration @ConditionalOnRefreshScope protected static class RefreshableEurekaClientConfiguration{ @Bean @RefreshScope public EurekaClient eurekaClient(...) { return new CloudEurekaClient(manager, config, this.optionalArgs, this.context); } @Bean @RefreshScope public ApplicationInfoManager eurekaApplicationInfoManager(...) { ... return new ApplicationInfoManager(config, instanceInfo); } }
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持脚本之家。
相关文章
SpringBoot(cloud)自动装配bean找不到类型的问题
这篇文章主要介绍了SpringBoot(cloud)自动装配bean找不到类型的问题,具有很好的参考价值,希望对大家有所帮助。如有错误或未考虑完全的地方,望不吝赐教2022-02-02详解SpringCloud LoadBalancer 新一代负载均衡器
这篇文章主要为大家介绍了SpringCloud LoadBalancer新一代负载均衡器详解使用详解,有需要的朋友可以借鉴参考下,希望能够有所帮助,祝大家多多进步,早日升职加薪2023-01-01Springboot中登录后关于cookie和session拦截问题的案例分析
这篇文章主要介绍了Springboot中登录后关于cookie和session拦截案例,本文通过实例图文相结合给大家介绍的非常详细,对大家的学习或工作具有一定的参考借鉴价值,需要的朋友可以参考下2020-08-08一篇文章教你将JAVA的RabbitMQz与SpringBoot整合
这篇文章主要介绍了如何将JAVA的RabbitMQz与SpringBoot整合,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧2021-09-09SpringBoot之logback-spring.xml不生效的解决方法
这篇文章主要介绍了SpringBoot之logback-spring.xml不生效的解决方法,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧2018-01-01细说Springcloud eureka的几种主动下线服务的方式
这篇文章主要介绍了细说Springcloud eureka的几种主动下线服务的方式,小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧2018-09-09
最新评论