Spring 拓展原理（BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor、ApplicationListener）

「爱情、让人受尽委屈。」 2023-02-17 03:45 7阅读 0赞

## BeanFactoryPostProcessor ##

**执行时机：**  
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；  
所有的bean定义已经保存加载到beanFactory，但是bean的实例还未创建

**BeanFactoryPostProcessor原理:**  
![在这里插入图片描述][20200612093423666.png]

代码示例： 执行 实际

@Component
    public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { 
    
    	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { 
    		System.out.println("MyBeanFactoryPostProcessor...postProcessBeanFactory...");
    		int count = beanFactory.getBeanDefinitionCount();
    		String[] names = beanFactory.getBeanDefinitionNames();
    		System.out.println("当前BeanFactory中有"+count+" 个Bean");
    		System.out.println(Arrays.asList(names));
    	}
    }

public class MyTest { 
    
        @Test
        public void test01 () { 
            AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(ExtConfig.class);
            applicationContext.close();
        }
    }

@ComponentScan("com.fyj.spring.annotation.ext")
    @Configuration
    public class ExtConfig { 
    	
    	@Bean
    	public Blue blue(){ 
    		return new Blue();
    	}
    
    }

执行结果：  
在 Blue 初始化之前执行  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70]

## BeanDefinitionRegistryPostProcessor ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 1]

## ApplicationListener ##

![在这里插入图片描述][20200612102515804.png]

**步骤：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 2]

### 原理 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 3]

**事件多播器（派发器）**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 4]

@Component
    public class MyApplicationListener implements ApplicationListener<ApplicationEvent> { 
    
        // 当容器发布此事件以后，方法触发
        public void onApplicationEvent(ApplicationEvent event) { 
            System.out.println("收到事件：" + event);
        }
    }

运行结果：  
![在这里插入图片描述][20200612101721208.png]

[20200612093423666.png]: https://img-blog.csdnimg.cn/20200612093423666.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200612094255968.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200612095138120.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3,size_16,color_FFFFFF,t_70
[20200612102515804.png]: https://img-blog.csdnimg.cn/20200612102515804.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200612102532856.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20200612105257965.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20200612105325778.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Z5ajEzOTI1NDc1OTU3,size_16,color_FFFFFF,t_70
[20200612101721208.png]: https://img-blog.csdnimg.cn/20200612101721208.png