spring IOC - AnnotationConfigApplicationContext#refresh2
执行完前面的步骤后, 回到 org.springframework.context.support.AbstractApplicationContext#refresh 方法.
@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. //准备工作包括设置启动时间，是否激活标识位, 初始化属性源(property source)配置 //不重要 prepareRefresh(); // Tell the subclass to refresh the internal bean factory. //返回一个factory - 为什么需要返回一个工厂 //因为要对工厂进行初始化 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. //为beanFactory设置一些属性如ClassLoader,BeanExpressionResolver,PropertyEditorRegistrar,BeanPostProcessor等 //准备工厂 prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. //这个方法在当前版本的spring是没用任何代码的 //可能spring期待在后面的版本中去扩展吧 postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. //为beanFactory注册BeanFactoryPostProcessor //在spring的环境中去执行已经被注册的 factory processors //设置执行自定义的ProcessBeanFactory 和spring内部自己定义的 invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. //按照顺序注册当Bean创建时候的BeanPostProcessor //1. 注册实现了 PriorityOrdered 接口的后置处理器 //2. 注册实现了 Ordered 接口的后置处理器 //3. 注册其他的后置处理器 registerBeanPostProcessors(beanFactory); // Initialize message source for this context. //初始化上下文的消息源：DelegatingMessageSource initMessageSource(); // Initialize event multicaster for this context. //初始化了一个事件广播器：SimpleApplicationEventMulticaster initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. //空方法, 留着后面扩展用的 onRefresh(); // Check for listener beans and register them. //获取ApplicationListener，并在事件传播器中注册他们 registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. //获取LoadTimeWeaverAware并初始化他们，初始化单例并且非懒加载的Bean finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event. //完成refresh Context操作，初始化LifecycleProcessor并start，发布ContextRefreshedEvent事件 finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } // Destroy already created singletons to avoid dangling resources. destroyBeans(); // Reset 'active' flag. cancelRefresh(ex); // Propagate exception to caller. throw ex; } finally { // Reset common introspection caches in Spring's core, since we // might not ever need metadata for singleton beans anymore... //主要是清理缓存 resetCommonCaches(); } } }
refresh 方法, 除了 invokeBeanFactoryPostProcessors() 比较重要外, 还有一个很重要的方法: finishBeanFactoryInitialization(beanFactory)
其他的几个方法, 看看就行, 都是一些注册, 初始化一些默认属性什么的, 属于前期的配置工作.
finishBeanFactoryInitialization
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) { // Initialize conversion service for this context. if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) && beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) { beanFactory.setConversionService( beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)); } // Register a default embedded value resolver if no bean post-processor // (such as a PropertyPlaceholderConfigurer bean) registered any before: // at this point, primarily for resolution in annotation attribute values. if (!beanFactory.hasEmbeddedValueResolver()) { //设置一个内置的类型转换器 : StringValueResolver beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal)); } // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early. // aspectj的, 基本用不着 String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false); for (String weaverAwareName : weaverAwareNames) { getBean(weaverAwareName); } // Stop using the temporary ClassLoader for type matching. beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes. // 冻结配置 beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons. //实例化所有的单例对象 beanFactory.preInstantiateSingletons(); }
preInstantiateSingletons 方法中, 就回去实例化容器里面注册的 bean.
//org.springframework.beans.factory.support.DefaultListableBeanFactory#preInstantiateSingletons @Override public void preInstantiateSingletons() throws BeansException { if (logger.isTraceEnabled()) { logger.trace("Pre-instantiating singletons in " + this); } //所有bean的名字 // Iterate over a copy to allow for init methods which in turn register new bean definitions. // While this may not be part of the regular factory bootstrap, it does otherwise work fine. List<String> beanNames = new ArrayList<>(this.beanDefinitionNames); // Trigger initialization of all non-lazy singleton beans... // 触发所有非延迟加载单例beans的初始化，主要步骤为调用getBean for (String beanName : beanNames) { //属性合并 : 合并父 BeanDefinition, xml中 bean 配置 parent="" RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); // 非抽象 & 单例 & 非懒加载 if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { if (isFactoryBean(beanName)) { //如果是FactoryBean则加上& Object bean = getBean(FACTORY_BEAN_PREFIX + beanName); if (bean instanceof FactoryBean) { final FactoryBean<?> factory = (FactoryBean<?>) bean; boolean isEagerInit; if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) { isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit, getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } if (isEagerInit) { getBean(beanName); } } } else { getBean(beanName); } } } // Trigger post-initialization callback for all applicable beans... //当所有的bean都完成创建后, 调用他们的 SmartInitializingSingleton 接口的 afterSingletonsInstantiated 方法 for (String beanName : beanNames) { Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<Object>) () -> { smartSingleton.afterSingletonsInstantiated(); return null; }, getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } }
这里注意到两个点:
1. 首先遍历了容器里面注册的 beanName , 然后通过 getBean() 的方式, 将 beanName 转化成 bean.
2. 然后遍历所有的 bean, 调用其 SmartInitializingSingleton#afterSingletonsInstantiated() , 进行最后的初始化调用
