【springboot源码分析】4.Bean的感知类执行(Aware)

springboot启动最核心的方法是AstractApplicationContext中的refresh方法，它贯穿Bean的整个生命周期

// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);

// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// 执行Bean工厂后置处理器，并注册BeanDefinition
invokeBeanFactoryPostProcessors(beanFactory);

// 注册Bean后置处理器
registerBeanPostProcessors(beanFactory);

// Initialize message source for this context.
initMessageSource();

// Initialize event multicaster for this context.
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
onRefresh();

// Check for listener beans and register them.
registerListeners();

// Bean实例化
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.
finishRefresh();

说到感知类的执行就需要提到prepareBeanFactory(beanFactory)方法，该方法里面注册了一个Bean后置处理器ApplicationContextAwareProcessor

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    ......
	// Configure the bean factory with context callbacks.
	beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
	......
}

该后置处理器在每个Bean初始化之前会调用一系列该Bean实现了的感知类

可以查看调用ApplicationContextAwareProcessor后置处理器执行了什么操作

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;
}

它里面调用了invokeAwareInterfaces(bean)方法，该方法里面就是调用Bean实现了得感知类，可以看看有哪些感知类

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);
		}
	}
}