【springboot源碼分析】4.Bean的感知類執行(Aware)

springboot啓動最核心的方法是AstractApplicationContext中的refresh方法，它貫穿Bean的整個生命週期

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

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

// 執行Bean工廠後置處理器，並註冊BeanDefinition
invokeBeanFactoryPostProcessors(beanFactory);

// 註冊Bean後置處理器
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實例化
finishBeanFactoryInitialization(beanFactory);

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

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說到感知類的執行就需要提到prepareBeanFactory(beanFactory)方法，該方法裏面註冊了一個Bean後置處理器ApplicationContextAwareProcessor

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

該後置處理器在每個Bean初始化之前會調用一系列該Bean實現了的感知類

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可以查看調用ApplicationContextAwareProcessor後置處理器執行了什麼操作

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;
}

它裏面調用了invokeAwareInterfaces(bean)方法，該方法裏面就是調用Bean實現了得感知類，可以看看有哪些感知類

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);
		}
	}
}

是不是有一種很熟悉的感覺，這些感知類的執行是在Bean實例化之後，Bean初始化之前執行的，該後置處理器執行的這些感知類會後於一些感知類的執行，具體是哪些需要在Bean初始化的時候才能知道