當Bean 定義資源被載入IOC 容器之后， 容器將Bean 定義資源解析為容器內部的數據結構BeanDefinition 注冊到容器中，AbstractApplicationContext 類中的finishBeanFactoryInitialization()方法對配置了預實例化屬性的Bean 進行預初始化過程，源碼如下：

//對配置了lazy-init屬性的Bean進行預實例化處理 protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {// Initialize conversion service for this context.//這是Spring3以后新加的代碼，為容器指定一個轉換服務(ConversionService)//在對某些Bean屬性進行轉換時使用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()) {beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));}// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);for (String weaverAwareName : weaverAwareNames) {getBean(weaverAwareName);}// Stop using the temporary ClassLoader for type matching.//為了類型匹配，停止使用臨時的類加載器beanFactory.setTempClassLoader(null);// Allow for caching all bean definition metadata, not expecting further changes.//緩存容器中所有注冊的BeanDefinition元數據，以防被修改beanFactory.freezeConfiguration();// Instantiate all remaining (non-lazy-init) singletons.//對配置了lazy-init屬性的單態模式Bean進行預實例化處理beanFactory.preInstantiateSingletons(); }

ConfigurableListableBeanFactory 是一個接口， 其preInstantiateSingletons() 方法由其子類DefaultListableBeanFactory 提供。

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