Spring Aware接口执行时机

一. 介绍

Spring Aware 接口的执行时机有两处，都在 getBean() 中的 initializeBean() 中；

下面我们分析这两处时机；

// ----------------------- AbstractAutowireCapableBeanFactory ---------------------
protected Object initializeBean(String beanName, Object bean, RootBeanDefinition mbd) {// 1. 时机一，invokeAwareMethods()invokeAwareMethods(beanName, bean);Object wrappedBean = bean;if (mbd == null || !mbd.isSynthetic()) {// 2. 时机二，BeanPostProcessor 的 postProcessBeforeInitialization()// 处理 aware bean 的是 ApplicationContextAwareProcessorwrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);}try {// 执行 bean 的 init-methodinvokeInitMethods(beanName, wrappedBean, mbd);}catch (Throwable ex) {throw new BeanCreationException((mbd != null ? mbd.getResourceDescription() : null), beanName, ex.getMessage(), ex);}if (mbd == null || !mbd.isSynthetic()) {wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);}return wrappedBean;
}

二. invokeAwareMethods()

时机一，我们看下这个方法会处理几种 Aware bean 对象；

会处理三种 Aware bean，分别是：BeanNameAware、BeanClassLoaderAware、BeanFactoryAware；

// ----------------------- AbstractAutowireCapableBeanFactory ---------------------
private void invokeAwareMethods(String beanName, Object bean) {if (bean instanceof Aware) {if (bean instanceof BeanNameAware beanNameAware) {beanNameAware.setBeanName(beanName);}if (bean instanceof BeanClassLoaderAware beanClassLoaderAware) {ClassLoader bcl = getBeanClassLoader();if (bcl != null) {beanClassLoaderAware.setBeanClassLoader(bcl);}}if (bean instanceof BeanFactoryAware beanFactoryAware) {beanFactoryAware.setBeanFactory(AbstractAutowireCapableBeanFactory.this);}}
}

三. ApplicationContextAwareProcessor

ApplicationContextAwareProcessor 是一个处理 Aware 接口的 BeanPostProcessor，我们直接看它的 postProcessBeforeInitialization()；

// --------------------------- ApplicationContextAwareProcessor -----------------------------
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware ||bean instanceof ApplicationStartupAware)) {return bean;}invokeAwareInterfaces(bean);return bean;
}// --------------------------- ApplicationContextAwareProcessor -----------------------------
private void invokeAwareInterfaces(Object bean) {if (bean instanceof Aware) {// EnvironmentAware：系统环境if (bean instanceof EnvironmentAware environmentAware) {environmentAware.setEnvironment(this.applicationContext.getEnvironment());}if (bean instanceof EmbeddedValueResolverAware embeddedValueResolverAware) {embeddedValueResolverAware.setEmbeddedValueResolver(this.embeddedValueResolver);}if (bean instanceof ResourceLoaderAware resourceLoaderAware) {resourceLoaderAware.setResourceLoader(this.applicationContext);}// ApplicationEventPublisherAware：事件发布if (bean instanceof ApplicationEventPublisherAware applicationEventPublisherAware) {applicationEventPublisherAware.setApplicationEventPublisher(this.applicationContext);}if (bean instanceof MessageSourceAware messageSourceAware) {messageSourceAware.setMessageSource(this.applicationContext);}if (bean instanceof ApplicationStartupAware applicationStartupAware) {applicationStartupAware.setApplicationStartup(this.applicationContext.getApplicationStartup());}// ApplicationContextAware：Spring 的 ApplicationContext 容器if (bean instanceof ApplicationContextAware applicationContextAware) {applicationContextAware.setApplicationContext(this.applicationContext);}}
}