Spring和SpringBoot的重要回调机制

一、启动回调

应用场景：

1.启动前环境检测？

2.启动时配置初始化？

3.启动后数据初始化？

 

类型	注入方式	回调时机	总体回调顺序	应用场景
ApplicationContextInitializer	spring.factories 等3种	IOC容器初始化时被回调	1	启动前环境检测
SpringApplicationRunListener	spring.factories	springboot启动过程中被多次回调	贯穿整个过程，最开始到最后	非常灵活，比如启动时配置初始化
ApplicationRunner	IOC容器，及类加注解@Component	容器启动完成后被回调	2	启动后数据初始化
CommandLineRunner	IOC容器，及类加注解@Component	ApplicationRunner后被回调	3	启动后数据初始化
ApplicationReadyEvent	IOC容器，及类加注解@Component implements ApplicationListener<ApplicationReadyEvent>	在CommandLineRunner后 SpringApplicationRunListener...running前	4	启动后数据初始化

 

回调顺序：

SpringApplicationRunListener...starting...

SpringApplicationRunListener...environmentPrepared..Windows 10

ApplicationContextInitializer:...run....

SpringApplicationRunListener...contextPrepared...

SpringApplicationRunListener...contextLoaded...

SpringApplicationRunListener...started...

ApplicationRunner1...run....

ApplicationRunner2...run....

CommandLineRunner...run...[]

onApplicationEvent-ApplicationReadyEvent...run....

SpringApplicationRunListener...running...

 

二、Bean后置处理

 BeanFactoryPostProcessor和BeanPostProcessor

•  BeanFactoryPostProcessor

1..功能：对BeanFactory扩展后置处理

2.子接口扩展：BeanDefinitionRegistryPostProcessor，增加对BeanDefinitionRegistry的扩展处理

3.典型实现类：ConfigurationClassPostProcessor

4.源码实现：

org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
　　　　　// 添加和执行BeanFactoryPostProcessor
        PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

        // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
        // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
        if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }
    }

 

关键方法：PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors

invokeBeanFactoryPostProcessors主要做的就是执行BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor的2个扩展方法，按照主要排序、排序、无顺序要求的三类BeanFactoryPostProcessor执行。这些BeanFactoryPostProcessors可能是内部Spring实现添加好的，也可能是来自ClassPath扫描出来的BeanFactoryPostProcessors

• BeanPostProcessor

1.功能：对Bean扩展后置处理

2.子接口扩展：

MergedBeanDefinitionPostProcessor

InstantiationAwareBeanPostProcessor

DestructionAwareBeanPostProcessor

3.典型实现类：

AutowiredAnnotationBeanPostProcessor

InitDestroyAnnotationBeanPostProcessor

CommonAnnotationBeanPostProcessor

4.源码实现：

org.springframework.context.support.AbstractApplicationContext#registerBeanPostProcessors

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
　　PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}

　　

关键方法：PostProcessorRegistrationDelegate.registerBeanPostProcessors

 

三、Bean生命周期回调

• Spring接口扩展InitializingBean.afterPropertiesSet(),DisposableBean.destroy()

• 基于JSR- 250注解@PostConstruct,@PreDestroy

• 基于Spring xml配置init,destroy方法

四、Aware回调操作

比如：ApplicationContextAware、EnvironmentAware等