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在spring中关于后置处理器主要有两个接口BeanFactoryPostProcessor、BeanPostProcessor。

BeanFactoryPostProcessor与BeanPostProcessor的区别

引用spring源码中的类注释

BeanFactoryPostProcessor类注释

/**
 * Allows for custom modification of an application context's bean definitions,
 * adapting the bean property values of the context's underlying bean factory.
 *
 * <p>Application contexts can auto-detect BeanFactoryPostProcessor beans in
 * their bean definitions and apply them before any other beans get created.
 ......
 *
 * <p>A BeanFactoryPostProcessor may interact with and modify bean
 * definitions, but never bean instances. Doing so may cause premature bean
 * instantiation, violating the container and causing unintended side-effects.
 */

允许自定义修改应用程序上下文的bean定义，适配上下文中bean工厂属性的潜在bean。
应用程序上下文可以在它们的bean定义中自动检测BeanFactoryPostProcessor 实例，并在创建任何其他bean之前应用它们。
一个BeanFactoryPostProcessor后置处理器可以与bean定义交互和修改，但不能与bean实例交互修改。这样做可能导致过早bean实例化，造成意想不到的副作用。如果需要bean实例交互，请考虑实现BeanPostProcessor。

BeanPostProcessor类注释

/**
 * 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.
    ......
 */

工厂钩子，允许自定义修改新的bean实例；ApplicationContexts可以自动检测BeanPostProcessor bean定义中的BeanPostProcessor 实例，并将它们应用于随后创建的任何bean；普通bean工厂允许对后处理器进行编程注册，应用于通过该工厂创建的所有bean

总结

BeanFactoryPostProcessor：作用在容器内所有bean实例化之前；可以修改应用程序上下文的bean定义

BeanPostProcessor：作用在容器内所有bean实例化之后初始化之前；允许修改bean实例

▲注意：
BeanFactoryPostProcessor修改bean定义，BeanPostProcessor修改bean实例

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