Day63 Spring 启动过程解析

创建BeanFactory -- DefaultListableBeanFactory

注册，然后setXXX

addBeanDefinitionXXX ---> 存放到 BeanFactoy中

addBeanPostProcessor.

public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
        this();
        register(componentClasses);
        refresh();
    }

调用构造，注册实例，刷新容器。

1. 准备刷新 prepareRefresh();
   可以记录启动时间，允许子类添加内容到容器里面
2. 构建BeanFactory 做初始化操作
3. 构建BeanFactoryProcessor
4. onRefresh方法 空实现
5. 完成刷新，完成初始化，然后发送初始化完成推送

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BeanFactory对象

调用无参构造，创建一个DefaultListableBeanFactory.

构建BeanFactory对象(DefaultListableBeanFactory)解析后得到BeanDefinition,注册到BeanFactory中。

解析@ComponentScan,Import,Bean注解 .

ApplicationContext需要支持国家化，事件机制，所以还需要初始化Msg,ApplicationEventMulCa. ApplicationListener对象添加到ApplicationContext中，启动完毕后发布事件.

• Multicaster,Event，国际化资源

protected void registerListeners() {
        // Register statically specified listeners first.
        for (ApplicationListener<?> listener : getApplicationListeners()) {
            getApplicationEventMulticaster().addApplicationListener(listener);
        }

        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let post-processors apply to them!
        String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
        for (String listenerBeanName : listenerBeanNames) {
            getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
        }

        // Publish early application events now that we finally have a multicaster...
        Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
        this.earlyApplicationEvents = null;
        if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
            for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
                getApplicationEventMulticaster().multicastEvent(earlyEvent);
            }
        }
    }

        // Publish the final event.
        publishEvent(new ContextRefreshedEvent(this));

发布了ContextRefreshedEvent事件。

• CommonAnnotationBeanPostProcessor
  处理@Resource,@PostConstruct @PreDestory 注解
• AutowiredAnnotationBeanPostProcessor
  处理@AutoWired，@Value注解
• ApplicationContextAwareProcessor
  处理ApplicationContextAware回调

BeanFactoryPostProcessor

两个相近的接口

public class BeanFacPro implements BeanFactoryPostProcessor, BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        BeanDefinition beanDefinition = beanFactory.getBeanDefinition("");
        beanFactory.registerSingleton("a",beanDefinition);
    }
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        registry.registerBeanDefinition("",new RootBeanDefinition("value"));
    }
}

该步骤发生在生成了BeanDefinition，但是单例Bean没有创建出来的时机，所以修改BeanDefinition会生效.

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refresh

加载配置的资源，要么全部成功，要么失败后全部销毁

Lifecycle

SmartLifecycle可以监听ApplicationContext的启动和关闭