SpringCloud之RefreshScope 源码解读

SpringCloud之RefreshScope#

@Scope 源码解读#

• 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

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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

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@Target({ ElementType.TYPE, ElementType.METHOD }) @Retention(RetentionPolicy.RUNTIME) @Scope("refresh") @Documented public @interface RefreshScope { /** * @see Scope#proxyMode() * @return proxy mode */ ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS; }

• @Scope 的注册 AnnotatedBeanDefinitionReader#registerBean

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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

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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

  @RefreshScope 源码解读#

  RefreshScope注册#

• RefreshAutoConfiguration#RefreshScopeConfiguration

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@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

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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

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public synchronized Set<String> refresh() { Set<String> keys = refreshEnvironment(); this.scope.refreshAll(); return keys; } public synchronized Set<String> refreshEnvironment() { Map<String, Object> before = extract( this.context.getEnvironment().getPropertySources()); addConfigFilesToEnvironment(); Set<String> keys = changes(before, extract(this.context.getEnvironment().getPropertySources())).keySet(); this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys)); return keys; }

• 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
• ⑦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）
• ⑧RefreshScope#refreshAll

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public void refreshAll() { <b>super.destroy();</b> this.context.publishEvent(new RefreshScopeRefreshedEvent()); }

• ⑨GenericScope#destroy

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public void destroy() { ... Collection<BeanLifecycleWrapper> wrappers = <b>this.cache.clear()</b>; for (BeanLifecycleWrapper wrapper : wrappers) { <b>wrapper.destroy();</b> } }

 

来源：oschina

链接：https://my.oschina.net/xiaominmin/blog/3165213