后置处理器ApplicationContextAwareProcessor

在spring启动刷新的时候，会有一个准备工作也就是prepareBeanFactory方法，里面会添加BeanPostProcessor，也就是本文要说的ApplicationContextAwareProcessor

prepareBeanFactory(beanFactory);

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   
   
	....
	beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
	....
}

ApplicationContextAwareProcessor实现了BeanPostProcessor接口,所以在Bean实例化的前后会调用BeanPostProcessor的postProcessBeforeInitialization和postProcessAfterInitialization方法,ApplicationContextAwareProcessor中也会有这两个方法源码实例

ApplicationContextAwareProcessor会处理下面几种接口的实现类

 1. EnvironmentAware
 2. EmbeddedValueResolverAware
 3. ResourceLoaderAware
 4. ApplicationEventPublisherAware
 5. MessageSourceAware
 6. ApplicationContextAware

通过名字可以猜到大概，当我们实现上面的接口，就需要实现对应接口的方法，然后方法里面去拿到对应类的属性，比如ApplicationContextAware接口，需要重写setApplicationContext方法，就可以拿到ApplicationContext对象