Spring ApplicationContext下的一系列aware接口的调用

ApplicationContext的一系列aware回调接口,是通过实现BeanPostProcessor来实现的，当bean工厂启动后实力化BEAN就会回调这一系列的aware接口

class ApplicationContextAwareProcessor implements BeanPostProcessor {

//当bean实例化之前，会调用此方法对bean进行处理
这是官方的解释：
Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean * initialization callbacks (like InitializingBean's <code>afterPropertiesSet</code> * or a custom init-method)

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(new PrivilegedAction<Object>() {
				public Object run() {
					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(
						new EmbeddedValueResolver(this.applicationContext.getBeanFactory()));
			}
			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);
			}
		}
	}

}

可以看到所有的aware接口统统在此处回调,哪这个类到底在哪里会被调用呢？
在AbstractAutowireCapableBeanFactory里面
方法如下：

public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessBeforeInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}

这里是总的入口，但是ApplicationContextAwareProcessor的实例是什么时候到AbstractAutowireCapableBeanFactory的getBeanPostProcessors返回的集合里面的呢？
答案还得回到AbstractApplicationContext类里面

public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
                        //此处就是调用的地方
			prepareBeanFactory(beanFactory);
    .....................................................
}
实现为：
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
.............省略其他的代码...........
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
.............省略其他的代码...........
}

在这里就将该实例该ApplicationContextAwareProcessor实例绑定到了beanFactory上了，所以当beanfactory回调beanPostProcess接口的时候，就可以执行这里面的postProcessBeforeInitialization方法了。