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

ゞ浴缸里的玫瑰 2022-05-01 13:48 146阅读 0赞

![644566-20190120091500694-1259457747.png][]

**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**

1.   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。
2.   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。
3.  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;
        }
    }

[644566-20190120091500694-1259457747.png]: /images/20220119/08f517e75a4344c7ae760d1d07438830.png