小明：“妈，我被公司开除了”，妈：“啊，为什么呀？”， 小明：“我骂董事长是笨蛋，公司召开高层会议还要起诉我”，妈：“告你诽谤是吧？”，小明：“不是，他们说要告我泄露公司机密”
不管三七二十一，我们先来看看它的定义，看看spring是如何描述BeanPostProcessor的
/* * Copyright 2002-2016 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.beans.factory.config; import org.springframework.beans.BeansException; import org.springframework.lang.Nullable; /** * 允许对新的bean示例进行自定义的修改，例如检查标志接口或进行代理封装 * * spring上下文会在它的beng定义中自动检测BeanPostProcessor实例，并将它们应用于随后创建的每一个bean实例 * * implement {@link #postProcessAfterInitialization}. * 通常，通过实现BeanPostProcessor的postProcessBeforeInitialization方法（配合标记接口，如@Autowired）来填充bean实例， * 通过BeanPostProcessor的postProcessAfterInitialization方法进行bean实例的代理 * */ public interface BeanPostProcessor { /** * 在bean实例的初始化方法（例如InitializingBean的afterPropertiesSet或自定义的init-method）回调之前， * spring会应用此方法到bean实例上。一般用于bean实例的属性值的填充 * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean * initialization callbacks (like InitializingBean's {@code afterPropertiesSet} * or a custom init-method). The bean will already be populated with property values. * The returned bean instance may be a wrapper around the original. * <p>The default implementation returns the given {@code bean} as-is. * @param bean the new bean instance * @param beanName the name of the bean * @return the bean instance to use, either the original or a wrapped one; * if {@code null}, no subsequent BeanPostProcessors will be invoked * @throws org.springframework.beans.BeansException in case of errors * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet */ @Nullable default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { return bean; } /** * 在bean实例的初始化方法（例如InitializingBean的afterPropertiesSet或自定义的init-method）回调之后， * spring会应用此方法到bean实例上。 * 在有FactoryBean时，此方法会在FactoryBean实例与FactoryBean的目标对象创建时各调用一次 * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean * initialization callbacks (like InitializingBean's {@code afterPropertiesSet} * or a custom init-method). The bean will already be populated with property values. * The returned bean instance may be a wrapper around the original. * <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean * instance and the objects created by the FactoryBean (as of Spring 2.0). The * post-processor can decide whether to apply to either the FactoryBean or created * objects or both through corresponding {@code bean instanceof FactoryBean} checks. * <p>This callback will also be invoked after a short-circuiting triggered by a * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method, * in contrast to all other BeanPostProcessor callbacks. * <p>The default implementation returns the given {@code bean} as-is. * @param bean the new bean instance * @param beanName the name of the bean * @return the bean instance to use, either the original or a wrapped one; * if {@code null}, no subsequent BeanPostProcessors will be invoked * @throws org.springframework.beans.BeansException in case of errors * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet * @see org.springframework.beans.factory.FactoryBean */ @Nullable default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { return bean; } }