BeanPostProcessor学习

/**
* Factory hook that allows for custom modification of new bean instances,
* e.g. checking for marker interfaces or wrapping them with proxies.
* 大体意思是可以检查相应的标识接口完成一些自定义功能实现，如包装目标对象到代理对象。
*/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.
    * <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
    */
   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.
* <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
*/
   Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;}