BeanFactoryPostProcessor

bean工厂后置处理器：干预beanFactory的工作流程（默认就是干预DefaultListableBeanFactory）

BeanFactoryPostProcessor是个接口，可以被继承，从而实现更多的功能，比如BeanDefinitionRegistryPostProcessor

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

    /**
     * Modify the application context's internal bean definition registry after its
     * standard initialization. All regular bean definitions will have been loaded,
     * but no beans will have been instantiated yet. This allows for adding further
     * bean definitions before the next post-processing phase kicks in.
     * @param registry the bean definition registry used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
     */
    void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}

其中一个实现类ConfigurationClassPostProcessor

/**
 * {@link BeanFactoryPostProcessor} used for bootstrapping processing of
 * {@link Configuration @Configuration} classes.
 *
 * <p>Registered by default when using {@code <context:annotation-config/>} or
 * {@code <context:component-scan/>}. Otherwise, may be declared manually as
 * with any other BeanFactoryPostProcessor.
 *
 * <p>This post processor is priority-ordered as it is important that any
 * {@link Bean} methods declared in {@code @Configuration} classes have
 * their corresponding bean definitions registered before any other
 * {@link BeanFactoryPostProcessor} executes.
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @author Phillip Webb
 * @since 3.0
 */
public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
        PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {

beanFactoryPostProcessor的作用

1. 修改BeanDefinition
2. 注册BeanDefinition
3. cglib代理
4. 其它更多的扩展功能

Spring 内置的 bean

• org.springframework.context.annotation.ConfigurationClassPostProcessor
• org.springframework.context.event.DefaultEventListenerFactory
• org.springframework.context.event.EventListenerMethodProcessor
• org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor
• org.springframework.context.annotation.CommonAnnotationBeanPostProcessor

ConfigurationClassPostProcessor

ConfigurationClassPostProcessor实现了很多接口, 两个重要接口

• BeanDefinitionRegistryPostProcessor （继承了BeanFactoryPostProcessor）
• BeanFactoryPostProcessor

由于BeanDefinitionRegistryPostProcessor是继承了BeanFactoryPostProcessor所以也可以理解这是一个接口

refresh 12个方法中的invokeBeanFactoryPostProcessors(beanFactory);

显示遍历找到BeanDefinitionRegistryPostProcessor，目前就是一个ConfigurationClassPostProcessor，然后执行一次

执行到invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);前后beanDefinitionMap有变化

可以看到执行完：自动被扫描的bean和一个自定义的BeanFactoryPostProcessor加入进来了

源码中：currentRegistryProcessors（就是ConfigurationClassPostProcessor），然后执行了ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法，该方法就是BeanDefinitionRegistryPostProcessor接口方法

1. 获取全注解类的bean(@Configuration), 当然有全注解类且之前已经加入到beanDefinitionMap中了，本例中就是postProcessorConfigLifebean
2. 根据全注解类bean构造一个ConfigurationClassBeanDefinitionReader的reader直接读取到当次能读取到的bean加入到beanDefinitionMap中，显然第一次就是只能获取到indexService和selfBeanFactoryPostProcessor

在最后可以看到要去执行自定义的beanPostProcessor

可以看到这次执行的是BeanFactoryPostProcessor接口的postProcessBeanFactory方法

所以最后可以看到refresh的12个方法中的invokeBeanFactoryPostProcessors(beanFactory);执行完则完成了所有bean加入到了beanDefinitionMap中去了