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  • spring BeanPostProcessor接口

    在上篇spring ApplicationListener接口(续)的例子中demo同时还实现了BeanPostProcessor接口

    实现了这个接口,在spring 启动时,实现了这个接口的方法同样也会被调用,不同的是实现这个接口的类,每个bean初始化的时候都会被调用一次

    先看一个这个接口的定义

    /**
     * Factory hook that allows for custom modification of new bean instances,
     * e.g. checking for marker interfaces or wrapping them with proxies.
     *
     * <p>ApplicationContexts can autodetect BeanPostProcessor beans in their
     * bean definitions and apply them to any beans subsequently created.
     * Plain bean factories allow for programmatic registration of post-processors,
     * applying to all beans created through this factory.
     *
     * <p>Typically, post-processors that populate beans via marker interfaces
     * or the like will implement {@link #postProcessBeforeInitialization},
     * while post-processors that wrap beans with proxies will normally
     * implement {@link #postProcessAfterInitialization}.
     *
     * @author Juergen Hoeller
     * @since 10.10.2003
     * @see InstantiationAwareBeanPostProcessor
     * @see DestructionAwareBeanPostProcessor
     * @see ConfigurableBeanFactory#addBeanPostProcessor
     * @see BeanFactoryPostProcessor
     */
    public interface BeanPostProcessor {
    
        /**
         * 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.
         * @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
         */
        Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;
    
        /**
         * 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.
         * @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
         */
        Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;
    
    }

    这个接口就两个方法before和after,实现了这个接口则可以对方法进行包装拦截。但是最后一定要返回一个bean否则创建的bean就为空了

    我就是最开始before方法直接返回空了,怎么搞控制台什么都没有

    同样是上篇的例子输出如下

    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    dubbo-consumer
    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    com.alibaba.dubbo.config.RegistryConfig
    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    org.springframework.context.event.internalEventListenerProcessor
    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    org.springframework.context.event.internalEventListenerFactory
    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    dubbo
    ++++++++++++++++++++++postProcessAfterInitialization ++++++++++++++++++++++++++
    myRealBean

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  • 原文地址:https://www.cnblogs.com/liguangming/p/10149243.html
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