BeanPostProcessor

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BeanPostProcessor接口

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public interface BeanPostProcessor {

	/**
	 * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
	 * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
	 * or a custom init-method).
	 * @param bean the new bean instance
	 * @param beanName the name of the bean
	 * @return the bean instance to use, either the original or a wrapped one; if
	 * {@code null}, no subsequent BeanPostProcessors will be invoked
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
	 */
	Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

	/**
	 * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean
	 * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
	 * or a custom init-method). 
	 * @param bean the new bean instance
	 * @param beanName the name of the bean
	 * @return the bean instance to use, either the original or a wrapped one; if
	 * {@code null}, no subsequent BeanPostProcessors will be invoked
	 * @throws org.springframework.beans.BeansException in case of errors
	 * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
	 * @see org.springframework.beans.factory.FactoryBean
	 */
	Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

BeanPostProcessor的注册

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//TODO

BeanPostProcessor的调用

图

bean创建过程中涉及到的BeanPostProcessor

"

详细

  1. factory.getObject后调用postprocessor.postProcessAfterInitialization

  2. doCreateBean之前调用InstantiationAwareBeanPostProcessor

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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.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			Class<?> targetType = determineTargetType(beanName, mbd);
			if (targetType != null) {
				bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
				if (bean != null) {
					bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
				}
			}
		}
		mbd.beforeInstantiationResolved = (bean != null);
	}
	return bean;
}
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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;
}
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@Override
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;
}
  1. createBeanInstance中在调用构造器之前调用Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName)
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protected Constructor<?>[] determineConstructorsFromBeanPostProcessors(Class<?> beanClass, String beanName)
			throws BeansException {

		if (beanClass != null && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
					SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
					Constructor<?>[] ctors = ibp.determineCandidateConstructors(beanClass, beanName);
					if (ctors != null) {
						return ctors;
					}
				}
			}
		}
		return null;
	}
  1. 在实例化后，(缓存实例化)填充属性前调用applyMergedBeanDefinitionPostProcessors来允许修改MergedBeanDefinition
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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);
		}
	}
  1. 在缓存实例化引用的时候,允许对缓存的实例化进行修改/代理
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addSingletonFactory(beanName, new ObjectFactory<Object>() {
	@Override
	public Object getObject() throws BeansException {
		return getEarlyBeanReference(beanName, mbd, bean);
	}
});
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protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
		Object exposedObject = bean;
		if (bean != null && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
					SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
					exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
					if (exposedObject == null) {
						return exposedObject;
					}
				}
			}
		}
		return exposedObject;
	}
  1. 在autowireByName/autowireByType前后，可以让InstantiationAwareBeanPostProcessors有机会改动bean
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if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
	for (BeanPostProcessor bp : getBeanPostProcessors()) {
		if (bp instanceof InstantiationAwareBeanPostProcessor) {
			InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
			if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
				continueWithPropertyPopulation = false;
				break;
			}
		}
	}
}
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if (hasInstAwareBpps) {
	for (BeanPostProcessor bp : getBeanPostProcessors()) {
		if (bp instanceof InstantiationAwareBeanPostProcessor) {
			InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
			pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
			if (pvs == null) {
				return;
			}
		}
	}
}
  1. 在初始化bean(initializeBean)的时候,在调用the bean implements InitializingBean or a custom init method前后调用applyBeanPostProcessorsBeforeInitialization，applyBeanPostProcessorsAfterInitialization
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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;
}
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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;
}

BeanPostProcessor的应用

  • 创建AOP代理类AnnotaionAwareAspectJAutoProxyCreator

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