ApplicationContextAware的setApplicationContext方法是什么时候执行的

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ApplicationContextAware的setApplicationContext方法是什么时候执行的

可以肯定的是在从容器中getbean的过程中调用的，简单说下几个主要流程

1. getbean到调用bean后处理器
   getbean的流程参见下图，主要参考标红字体部分
   
   从图中可以看出，最后会调用initializeBeanf方法又会调用applyBeanPostProcessorsBeforeInitialization、applyBeanPostProcessorsAfterInitialization方法，也就是调用bean后处理器。
2. bean后处理器其中就有一个叫ApplicationContextAwareProcessor,其中的处理方法如下代码，就有调用到setApplicationContext方法

@Override
    @Nullable
    public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
        AccessControlContext acc = null;

        if (System.getSecurityManager() != null &&
                (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
                        bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
                        bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
            acc = this.applicationContext.getBeanFactory().getAccessControlContext();
        }

        if (acc != null) {
            AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
                invokeAwareInterfaces(bean);
                return null;
            }, acc);
        }
        else {
            invokeAwareInterfaces(bean);
        }

        return bean;
    }

    private void invokeAwareInterfaces(Object bean) {
        if (bean instanceof Aware) {
            if (bean instanceof EnvironmentAware) {
                ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
            }
            if (bean instanceof EmbeddedValueResolverAware) {
                ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
            }
            if (bean instanceof ResourceLoaderAware) {
                ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
            }
            if (bean instanceof ApplicationEventPublisherAware) {
                ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
            }
            if (bean instanceof MessageSourceAware) {
                ((MessageSourceAware) bean).setMessageSource(this.applicationContext);
            }
            if (bean instanceof ApplicationContextAware) {
                ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
            }
        }
    }

1. 你是不是会问ApplicationContextAwareProcessor什么时候放到容器中的，看org.springframework.context.support.AbstractApplicationContext#prepareBeanFactory方法中就放进来了

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // Tell the internal bean factory to use the context's class loader etc.
        beanFactory.setBeanClassLoader(getClassLoader());
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

        // Configure the bean factory with context callbacks.
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
        ······
    }

4.prepareBeanFactory又在org.springframework.context.support.AbstractApplicationContext#refresh方法中被调用，看是不是又回到容器初始化的入口了，整个流程是不是打通了