Spring4-bean生命周期-4- 实例化Bean后置处理器（继承BeanPostProcessor）InstantiationAwareBeanPostProcessor

一、接口：

public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {
    //调用时机为bean实例化(Instantiation)之前 
    //如果返回了bean实例, 则会替代原来正常通过target bean生成的bean的流程
    //典型的例如aop返回proxy对象. 此时bean的执行流程将会缩短, 只会执行 BeanPostProcessor#postProcessAfterInitialization接口完成初始化。
    Object postProcessBeforeInstantiation(Class<?> var1, String var2) throws BeansException;



    //调用时机为bean实例化(Instantiation)之后和任何初始化(Initialization)之前
    boolean postProcessAfterInstantiation(Object var1, String var2) throws BeansException;



    PropertyValues postProcessPropertyValues(PropertyValues var1, PropertyDescriptor[] var2, Object var3, String var4) throws BeansException;
}

二、InstantiationAwareBeanPostProcessor与BeanPostProcessor对比

BeanPostProcessor 执行时机为bean初始化（Initialization）阶段，日常可以拓展该接口对bean初始化进行定制化处理。
InstantiationAwareBeanPostProcessor 执行时机bean实例化（Instantiation）阶段，典型用于替换bean默认创建方式，例如aop通过拓展接口生成代理对应，主要用于基础框架层面。如果日常业务中需要拓展该，spring推荐使用适配器类InstantiationAwareBeanPostProcessorAdapter。
所有bean创建都会进行回调。

三、adapter

package com.ooo.life;

import java.beans.PropertyDescriptor;

import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter;

public class MyInstantiationAwareBeanPostProcessor extends
        InstantiationAwareBeanPostProcessorAdapter {

    public MyInstantiationAwareBeanPostProcessor() {
        super();
        System.out.println("这是InstantiationAwareBeanPostProcessorAdapter实现类构造器！！");
    }

    // 接口方法、实例化Bean之前调用
    @Override
    public Object postProcessBeforeInstantiation(Class beanClass,
                                                 String beanName) {
        System.out.println("InstantiationAwareBeanPostProcessor调用postProcessBeforeInstantiation方法");
        return null;
    }

    // 接口方法、实例化Bean之后调用
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName)
            {
        System.out.println("InstantiationAwareBeanPostProcessor调用postProcessAfterInitialization方法");
        return bean;
    }

    // 接口方法、设置某个属性时调用
    @Override
    public PropertyValues postProcessPropertyValues(PropertyValues pvs,
                                                    PropertyDescriptor[] pds, Object bean, String beanName)
            {
        System.out.println("InstantiationAwareBeanPostProcessor调用postProcessPropertyValues方法");
        return pvs;
    }
}

Spring4-bean生命周期-4- 实例化Bean后置处理器（继承BeanPostProcessor）InstantiationAwareBeanPostProcessor

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