Bean后置处理器 – SmartInstantiationAwareBeanPostProcessor#determineCandidateConstructors

spring在创建对象(org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBeanInstance)的时候, 使用了这个 构造函数后置处理器, 用来选择使用哪个构造函数的.

所以这个后置处理器的执行时机是: 对象实例化之前执行

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#determineConstructorsFromBeanPostProcessors

@Nullable
protected Constructor<?>[] determineConstructorsFromBeanPostProcessors(@Nullable 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;
}