Spring之【Bean后置处理器】

BeanPostProcessor

BeanPostProcessor的子接口

InstantiationAwareBeanPostProcessor

MergedBeanDefinitionPostProcessor

SmartInstantiationAwareBeanPostProcessor

DestructionAwareBeanPostProcessor

AutowiredAnnotationBeanPostProcessor

CommonAnnotationBeanPostProcessor

BeanPostProcessor

Spring提供的扩展点
提供了两个默认方法，将bean对象和beanName作为参数
Spring会在合适的时机执行对应的方法逻辑

java 复制代码

package org.springframework.beans.factory.config;

import org.springframework.beans.BeansException;
import org.springframework.lang.Nullable;

public interface BeanPostProcessor {

    // bean初始化前
	@Nullable
	default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		return bean;
	}

    // bean初始化后
	@Nullable
	default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		return bean;
	}

}

BeanPostProcessor的子接口

InstantiationAwareBeanPostProcessor

java 复制代码

package org.springframework.beans.factory.config;


public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {

    // bean实例化前
	@Nullable
	default Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
		return null;
	}

    // bean实例化后
	default boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
		return true;
	}

    
	@Nullable
	default PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName)
			throws BeansException {

		return null;
	}
}

MergedBeanDefinitionPostProcessor

java 复制代码

package org.springframework.beans.factory.support;

public interface MergedBeanDefinitionPostProcessor extends BeanPostProcessor {

	void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName);

	default void resetBeanDefinition(String beanName) {
	}

}

SmartInstantiationAwareBeanPostProcessor

java 复制代码

package org.springframework.beans.factory.config;

public interface SmartInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessor {

	@Nullable
	default Class<?> predictBeanType(Class<?> beanClass, String beanName) throws BeansException {
		return null;
	}

	@Nullable
	default Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName)
			throws BeansException {

		return null;
	}

	default Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {
		return bean;
	}
}

DestructionAwareBeanPostProcessor

java 复制代码

package org.springframework.beans.factory.config;

public interface DestructionAwareBeanPostProcessor extends BeanPostProcessor {

	void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException;

	default boolean requiresDestruction(Object bean) {
		return true;
	}

}

AutowiredAnnotationBeanPostProcessor

将该BeanPostProcessor对应的BeanDefinition存到容器中，也就是DefaultListableBeanFactory中的beanDefinitionMap集合中

AbstractApplicationContext中refresh方法的registerBeanPostProcessors步骤中实例化并初始化好AutowiredAnnotationBeanPostProcessor对象，放入AbstractBeanfactory中的beanPostProcessors集合中

解析@Autowired、@Value注解

CommonAnnotationBeanPostProcessor

将该BeanPostProcessor对应的BeanDefinition存到容器中，也就是DefaultListableBeanFactory中的beanDefinitionMap集合中

AbstractApplicationContext中refresh方法的registerBeanPostProcessors步骤中实例化并初始化好AutowiredAnnotationBeanPostProcessor对象，放入AbstractBeanfactory中的beanPostProcessors集合中

解析@Resource、@PostContruct、@PreDestroy