我们分析过registerListeners后，本文分析finishBeanFactoryInitialization方法。
该方法其将会拿到所有的beanDefinitionNames，遍历beanNames，其非抽象、是单例、未配置lazy_init属性或其值非true那么就会触发getBean的操作。最后会对其中是SmartInitializingSingleton 类型的触发其afterSingletonsInstantiated方法。
AbstractApplicationContext的finishBeanFactoryInitialization方法
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) { // Initialize conversion service for this context. // 尝试获取并设置conversionService-本文这里直接跳过 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. // 尝试为beanFactory增加EmbeddedValueResolver，比如PropertyPlaceholderConfigurer //本文这里也跳过 if (!beanFactory.hasEmbeddedValueResolver()) { beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal)); } // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early. // 获取并初始化LoadTimeWeaverAware-本文这里为空 String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false); for (String weaverAwareName : weaverAwareNames) { getBean(weaverAwareName); } // Stop using the temporary ClassLoader for type matching. // tempClassLoader置为null beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes. //configurationFrozen=true //frozenBeanDefinitionNames=this.beanDefinitionNames //也就意味着这些bean定义被冷冻，不再支持修改 beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons. //实例化所以非懒加载 单例 bean beanFactory.preInstantiateSingletons(); }
可以看到其对beanFactory做了一点配置后直接触发了preInstantiateSingletons方法。
DefaultListableBeanFactory的preInstantiateSingletons方法
@Override public void preInstantiateSingletons() throws BeansException { if (logger.isTraceEnabled()) { logger.trace("Pre-instantiating singletons in " + this); } // 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. // 拿到beanDefinitionNames List<String> beanNames = new ArrayList<>(this.beanDefinitionNames); // Trigger initialization of all non-lazy singleton beans... for (String beanName : beanNames) { // 获取bean定义 RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); // 非抽象、单例、非懒加载 if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { // 是否为工厂bean if (isFactoryBean(beanName)) { // FACTORY_BEAN_PREFIX = & 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) { // 判断是否需要急切实例化 isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit, getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } // 如果需要急切实例化，则触发getBean方法 if (isEagerInit) { getBean(beanName); } } } else { // 非工厂bean直接触发实例化流程 getBean(beanName); } } } // Trigger post-initialization callback for all applicable beans... 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(); } } } }
方法流程梳理如下：
记录beanDefinitionNames到List<String> beanNames；
遍历beanNames，如果其是非抽象、单例、非懒加载：
如果其是FactoryBean则判断是否需要急切初始化，如果是则触发getBean流程；
如果不是FactoryBean，则直接触发getBean流程
遍历beanNames获取每个beanName对应的实例，如果其是SmartInitializingSingleton类型，则触发其afterSingletonsInstantiated方法。
SmartInitializingSingleton接口提供了afterSingletonsInstantiated方法，允许你在所有常规单例bean实例化之后触发。这里与InitializingBean的afterPropertiesSet有明显区别哦。
