文章目录

Pre
org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor
InstantiationAwareBeanPostProcessor 注册过程源码分析
- postProcessBeforeInstantiation的执行时机源码解析
使用场景：创建代理类

Pre

Spring Boot - 扩展接口一览

org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor

注意下： Initialization 表示初始化（意思是对象已经生成）。 Instantiation 表示实例化（意思是对象还未生成）。

接口继承了BeanPostProcess接口 , 从方法上我们也可以看出 InstantiationAwareBeanPostProcessor 做了一些扩展。

BeanPostProcess接口只在bean的初始化阶段进行扩展（注入spring上下文前后），而InstantiationAwareBeanPostProcessor接口在此基础上增加了3个方法，使得扩展接口可以在实例化阶段和属性注入阶段

该类主要的扩展点有以下5个方法，主要在bean生命周期的两大阶段：实例化阶段和初始化阶段 ，

(1)实例化: 实例化的过程是一个创建Bean的过程,即调用Bean构造函数,单例的Bean入单例池中

(2)初始化: 初始化的过程是一个赋值的过程,即调用Bean的setter方法,设置Bean属性

InstantiationAwareBeanPostProcessor作用于过程(1)实例化前后; BeanPostProcessor用于过程(2)初始化前后

按调用顺序，我们来看一下

postProcessBeforeInstantiation：实例化bean之前，相当于new这个bean之前
postProcessAfterInstantiation：实例化bean之后，相当于new这个bean之后
postProcessPropertyValues： bean已经实例化完成，在属性注入时阶段触发， @Autowired,@Resource等注解原理基于此方法实现
postProcessBeforeInitialization：初始化bean之前，相当于把bean注入spring上下文之前
postProcessAfterInitialization：初始化bean之后，相当于把bean注入spring上下文之后

InstantiationAwareBeanPostProcessor 注册过程源码分析

我们还是从

org.springframework.context.support.AbstractApplicationContext#refresh

开始看，主要是下面两个方法

.......
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);.......// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

看下调用栈

org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors()BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);org.springframework.beans.factory.support.AbstractBeanFactory#getBeanorg.springframework.beans.factory.support.AbstractBeanFactory#doGetBean  org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean

createBean跟进去

@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.Object bean = resolveBeforeInstantiation(beanName, mbdToUse);if (bean != null) {return bean;}//省略....Object beanInstance = doCreateBean(beanName, mbdToUse, args);return beanInstance;}

通过上面的代码，我们可以看到在执行doCreateBean之前有resolveBeforelnstantiation方法; 看注释

// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.

resolveBeforelnstantiation判断执行InstantiationAwareBeanPostProcessor.postProcessBeforelInstantiationg接口方法实现;
doCreateBean创建bean方法;

postProcessBeforeInstantiation的执行时机源码解析

org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors()BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);org.springframework.beans.factory.support.AbstractBeanFactory#getBeanorg.springframework.beans.factory.support.AbstractBeanFactory#doGetBean  org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBeanorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#resolveBeforeInstantiation

重点看 resolveBeforeInstantiation

 /*** Apply before-instantiation post-processors, resolving whether there is a* before-instantiation shortcut for the specified bean.* @param beanName the name of the bean* @param mbd the bean definition for the bean* @return the shortcut-determined bean instance, or {@code null} if none*/@Nullableprotected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {Object bean = null;//如果beforeInstantiationResolved还没有设置或者是false（说明还没有需要在实例化前执行的操作）if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {// Make sure bean class is actually resolved at this point.// 判断是否有注册过InstantiationAwareBeanPostProcessor类型的beanif (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {Class<?> targetType = determineTargetType(beanName, mbd);if (targetType != null) {//执行bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);if (bean != null) {bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);}}}mbd.beforeInstantiationResolved = (bean != null);}return bean;}

继续 applyBeanPostProcessorsBeforeInstantiation

 /*** Apply InstantiationAwareBeanPostProcessors to the specified bean definition* (by class and name), invoking their {@code postProcessBeforeInstantiation} methods.* <p>Any returned object will be used as the bean instead of actually instantiating* the target bean. A {@code null} return value from the post-processor will* result in the target bean being instantiated.* @param beanClass the class of the bean to be instantiated* @param beanName the name of the bean* @return the bean object to use instead of a default instance of the target bean, or {@code null}* @see InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation*/@Nullableprotected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {// 循环处理for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {Object result = bp.postProcessBeforeInstantiation(beanClass, beanName);//只要有一个result不为null；后面的所有 后置处理器的方法就不执行了，直接返回(所以执行顺序很重要)if (result != null) {return result;}}return null;}

当然了也有 postProcessAfterInitialization

 @Overridepublic Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)throws BeansException {Object result = existingBean;for (BeanPostProcessor processor : getBeanPostProcessors()) {Object current = processor.postProcessAfterInitialization(result, beanName);if (current == null) {return result;}result = current;}return result;}

使用场景：创建代理类

 package com.artisan.bootspringextend.testextends;import com.artisan.bootspringextend.service.ArtisanServiceImpl;
import com.artisan.bootspringextend.service.ClassA;
import com.artisan.bootspringextend.service.ClassAInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
import org.springframework.cglib.proxy.Enhancer;
import org.springframework.context.annotation.Configuration;/*** @author 小工匠* @version 1.0* @description:* @date 2022/11/28 0:33* @mark: show me the code , change the world*/@Slf4j
@Configuration
public class ExtendInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {private static final String VALUE = "classA";@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {if (VALUE.equals(beanName)) {log.info("4  beanName {}-----> postProcessBeforeInitialization", beanName);}return bean;}@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {if (VALUE.equals(beanName)) {log.info("5   beanName {}-----> postProcessAfterInitialization", beanName);}return bean;}@Overridepublic Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {if (beanClass == ClassA.class) {log.info("1  beanName {} -----> postProcessBeforeInstantiation", beanName);Enhancer enhancer = new Enhancer();enhancer.setSuperclass(beanClass);enhancer.setCallback(new ClassAInterceptor());ClassA classA = (ClassA) enhancer.create();log.info("proxy created ---->{}", classA.toString());return classA;}return null;}@Overridepublic boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {if (VALUE.equals(beanName)) {log.info("2   beanName {}-----> postProcessAfterInstantiation", beanName);}return false;}@Overridepublic PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException {if (VALUE.equals(beanName)) {log.info("3   beanName {} -----> postProcessProperties", beanName);}return pvs;}
}

我们可以看到 InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation 生成了代理类后，直接执行了初始化后的动作 BeanPostProcessor#postProcessAfterInitialization 。

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Spring - InstantiationAwareBeanPostProcessor 扩展接口

文章目录

Pre

org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor

InstantiationAwareBeanPostProcessor 注册过程源码分析

postProcessBeforeInstantiation的执行时机源码解析

使用场景：创建代理类

Spring - InstantiationAwareBeanPostProcessor 扩展接口相关推荐

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Spring - InstantiationAwareBeanPostProcessor 扩展接口

文章目录

Pre

org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor

InstantiationAwareBeanPostProcessor 注册过程源码分析

postProcessBeforeInstantiation的执行时机源码解析

使用场景 ： 创建代理类

Spring - InstantiationAwareBeanPostProcessor 扩展接口相关推荐

最新文章

热门文章

使用场景：创建代理类