Spring createBean过程中BeanPostProcessor的处理机会

       Spring IOC在实例化bean的过程中，BeanPostProcessor有机会在bean Instantiation前后、initialize前后进行处理，下面了解下分别做了什么。

BeanPostProcessor处理时序图

       这里只涉及BeanPostProcessor处理，其他过程忽略：

其中，红色步骤为BeanPostProcessor的相关处理。

相关源码分析

AbstractAutowireCapableBeanFactory.java

// 实例化前的BeanPostProcessor处理，这里有机会返回bean的代理对象
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
	Object bean = null;
	if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
		// Make sure bean class is actually resolved at this point.
		if (mbd.hasBeanClass() && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			bean = applyBeanPostProcessorsBeforeInstantiation(mbd.getBeanClass(), beanName);
			if (bean != null) {
				bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
			}
		}
		mbd.beforeInstantiationResolved = (bean != null);
	}
	return bean;
}

protected Object applyBeanPostProcessorsBeforeInstantiation(Class beanClass, String beanName)
		throws BeansException {

	for (BeanPostProcessor bp : getBeanPostProcessors()) {
		if (bp instanceof InstantiationAwareBeanPostProcessor) {
			InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
			Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
			if (result != null) {
				return result;
			}
		}
	}
	return null;
}

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

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

AbstractAutowireCapableBeanFactory.java

// BeanPostProcessor有机会修改RootBeanDefinition mbd
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class beanType, String beanName)
		throws BeansException {

	try {
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			if (bp instanceof MergedBeanDefinitionPostProcessor) {
				MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
				bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
			}
		}
	}
	catch (Exception ex) {
		throw new BeanCreationException(mbd.getResourceDescription(), beanName,
				"Post-processing failed of bean type [" + beanType + "] failed", ex);
	}
}

AbstractAutowireCapableBeanFactory.java

// BeanPostProcessor在bean初始化前的处理
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;
}

// bean的初始化
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
		throws Throwable {

	boolean isInitializingBean = (bean instanceof InitializingBean);
	if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
		if (logger.isDebugEnabled()) {
			logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
		}
		if (System.getSecurityManager() != null) {
			try {
				AccessController.doPrivileged(new PrivilegedExceptionAction