PostProcessor的种类：

大类分为容器级别的后置处理器和 Bean 级别的后置处理器

BeanDefinitionRegistryPostProcessor

BeanDefinition 的自定义注册

/**
 * @author wsq
 * @version CustomizedBeanDefinitionRegistryPostProcessor.java  2020/6/29  上午9:02 上午
 * 这个功能可以做什么事情？可以在这个接口里面搜索第三方的 Class,并将这些Class注册进Spring 容器中，这样就可以在复用第三方
 * 代码；mybatis框架就是这么做的
 */
@Configuration
public class CustomizedBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {


   @Override
   public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
      Class<?> userClass = User.class;
      BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(userClass);
      GenericBeanDefinition definition = (GenericBeanDefinition) builder.getRawBeanDefinition();
      registry.registerBeanDefinition("user5", definition);
   }

   @Override
   public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

   }
}

BeanFactoryPostProcessor

容器后置处理器

BeanPostProcessor

Bean的后置处理器，容器创建的每个Bean实例，创建Bean已经是依赖注入部分的知识了。容器创建的Bean实例，后置器都会在调用容器初始化之前和Bean实例初始化之后，都可以从容器获得回调执行。

@Configuration
public class CustomizedBeanPostProcessor implements BeanPostProcessor {

   @Override
   public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
      System.out.println(beanName + "调用了 postProcessBeforeInitialization");
      //对 bean做任何操作，处理
      return bean;
   }

   @Override
   public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
      System.out.println(beanName + "调用了 postProcessAfterInitialization");
      //对 bean做任何操作，处理
      return bean;
   }
}

public static void main(String args[]) {
   System.out.println("Spring 项目成功编译！！！！走注解使用Spring");
   ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Entrance.class);
   WelcomeService ws = (WelcomeService) applicationContext.getBean("welcomeServiceImpl");
   ws.sayHello("wsq");
   WelcomeController controller = (WelcomeController) applicationContext.getBean("welcomeController");
   controller.doRequest();
   String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
   for (String beanDefinitionName : beanDefinitionNames) {
      System.out.println(beanDefinitionName);
   }
   User user5 = (User) applicationContext.getBean("user5");
   System.out.println("CustomizedBeanDefinitionRegistryPostProcessor 注册的额外对象" + user5);
}

输出：

Spring 项目成功编译！！！！走注解使用Spring
entrance调用了 postProcessBeforeInitialization
entrance调用了 postProcessAfterInitialization
welcomeServiceImpl调用了 postProcessBeforeInitialization
welcomeServiceImpl调用了 postProcessAfterInitialization
welcomeController调用了 postProcessBeforeInitialization
welcomeController调用了 postProcessAfterInitialization
welcomeDao调用了 postProcessBeforeInitialization
welcomeDao调用了 postProcessAfterInitialization
user5调用了 postProcessBeforeInitialization
user5调用了 postProcessAfterInitialization
Hellow :wsq
Hellow :来自Controller的调用问候
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
entrance
welcomeController
welcomeDao
customizedBeanDefinitionRegistryPostProcessor
customizedBeanPostProcessor
welcomeServiceImpl
user5
CustomizedBeanDefinitionRegistryPostProcessor 注册的额外对象cn.com.yuns.entity.User@2c34f934