BeanFactoryPostProcessor：beanFactory的后置处理器，在BeanFactory标准初始化之后调用，来定制和修改BeanFactory的内容，此时所有的bean定义已经保存并加载到beanFactory，但是bean的实例还未创建，beanFactory实际上就是spring的容器
public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// Prepare this context for refreshing.prepareRefresh();// Tell the subclass to refresh the internal bean factory.ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();// Prepare the bean factory for use in this context.prepareBeanFactory(beanFactory);try {// Allows post-processing of the bean factory in context subclasses.postProcessBeanFactory(beanFactory);// Invoke factory processors registered as beans in the context.invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.registerBeanPostProcessors(beanFactory);// Initialize message source for this context.initMessageSource();// Initialize event multicaster for this context.initApplicationEventMulticaster();// Initialize other special beans in specific context subclasses.onRefresh();// Check for listener beans and register them.registerListeners();// Instantiate all remaining (non-lazy-init) singletons.finishBeanFactoryInitialization(beanFactory);//实例化bean// Last step: publish corresponding event.finishRefresh();}catch (BeansException ex) {if (logger.isWarnEnabled()) {logger.warn("Exception encountered during context initialization - " +"cancelling refresh attempt: " + ex);}// Destroy already created singletons to avoid dangling resources.destroyBeans();// Reset 'active' flag.cancelRefresh(ex);// Propagate exception to caller.throw ex;}finally {// Reset common introspection caches in Spring's core, since we// might not ever need metadata for singleton beans anymore...resetCommonCaches();}}
}@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("MyBeanFactoryPostProcessor ... postProcessBeanFactory ...");int count = beanFactory.getBeanDefinitionCount();String[] names = beanFactory.getBeanDefinitionNames();System.out.println("定义了:" + count + "个bean,名字是:" + Arrays.asList(names));}}BeanPostProcessor也是后置处理期，但BeanPostProcessor的调用时机是在bean创建之后，执行bean的初始化方法的前后调用其前置方法和后置方法。
Java1.8之后interface的方法在定义时也可以有方法体了，有方法体的接口方法必须使用default修饰，类似于父类：
public interface NullablIenterface {// @Nullabledefault void sayHello(String name) {System.out.println("hello" + name);}public void sayBye();
}BeanFactoryPostProcessor的原理：
1)、ioc容器创建对象前：refresh()
2)、invokeBeanFactoryPostProcessors(beanFactory);
如何找到所有的BeanFactoryPostProcessor并执行他们的方法
1）、直接在BeanFactory中找到所有类型是BeanFactoryPostProcessor的组件，并执行它们的postProcessBeanFactory方法：要求实现BeanFactoryPostProcessor接口，并且被纳入到IOC容器管理
2）、在初始化创建其他组件前面执行：finishBeanFactoryInitialization(beanFactory);//初始化组件