spring注解开发-扩展原理(源码)

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1.BeanFactoryPostProcessor

BeanPostProcessor:bean后置处理器,bean创建对象初始化前后进行拦截工作的;

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;即所有的bean定义已经保存加载到beanFactory,但是bean的实例还未创建;

BeanFactoryPostProcessor原理:

1)IOC容器创建对象

2)调用AbstractApplicationContext的refresh()方法;

3)调用AbstractApplicationContext的invokeBeanFactoryPostProcessors(beanFactory)方法,然后调用PostProcessorRegistrationDelegate的invokeBeanFactoryPostProcessors()方法

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,并执行他们的方法

2)、在初始化创建其他组件前面执行

2.BeanDefinitionRegistryPostProcessor

它是BeanFactoryPostProcessor的子接口;在所有bean定义信息将要被加载,bean实例还未创建的时候触发;

所以它优先于BeanFactoryPostProcessor执行;利用BeanDefinitionRegistryPostProcessor可以给容器中再额外添加一些组件;

BeanDefinitionRegistry: Bean定义信息的保存中心,以后BeanFactory就是按照BeanDefinitionRegistry里面保存的每一个bean定义信息创建bean实例;

BeanDefinitionRegistryPostProcessor原理:

1)IOC容器创建对象

2)调用AbstractApplicationContext的refresh()方法中的invokeBeanFactoryPostProcessors(beanFactory);

3)从容器中获取到所有的BeanDefinitionRegistryPostProcessor组件。

//PostProcessorRegistrationDelegate.class
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

3.1)调用invokeBeanDefinitionRegistryPostProcessors依次触发所有的postProcessBeanDefinitionRegistry()方法

//PostProcessorRegistrationDelegate.class
private static void invokeBeanDefinitionRegistryPostProcessors(Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
        Iterator var2 = postProcessors.iterator();
        while(var2.hasNext()) {
            BeanDefinitionRegistryPostProcessor postProcessor = (BeanDefinitionRegistryPostProcessor)var2.next();
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }

    }

3.2)再来触发BeanFactoryPostProcessor的postProcessBeanFactory()方法;

//PostProcessorRegistrationDelegate.class
private static void invokeBeanFactoryPostProcessors(Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
        Iterator var2 = postProcessors.iterator();

        while(var2.hasNext()) {
            BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var2.next();
            postProcessor.postProcessBeanFactory(beanFactory);
        }

    }

4)再来从容器中找到BeanFactoryPostProcessor组件;然后依次触发postProcessBeanFactory()方法

//PostProcessorRegistrationDelegate.class
private static void invokeBeanFactoryPostProcessors(
            Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

        for (BeanFactoryPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessBeanFactory(beanFactory);
        }
    }

3.ApplicationListener

public interface ApplicationListener<E extends ApplicationEvent>

监听 ApplicationEvent 及其下面的子事件;

实现步骤:

1)写一个监听器(ApplicationListener实现类)来监听某个事件(ApplicationEvent及其子类)

@Component
public class MyApplicationListener implements ApplicationListener<ApplicationEvent> {

2)把监听器加入到容器; @Component

3)只要容器中有相关事件的发布,我们就能监听到这个事件;
ContextRefreshedEvent:容器刷新完成(所有bean都完全创建)会发布这个事件;
ContextClosedEvent:关闭容器会发布这个事件;

4)、发布一个事件:applicationContext.publishEvent();

applicationContext.publishEvent(new ApplicationEvent(new String("发布事件")) {
        });

事件原理:

1)ContextRefreshedEvent事件:

1.1)容器创建对象:refresh();

1.2)finishRefresh();容器刷新完成会发布ContextRefreshedEvent事件

//AbstractApplicationContext.class
publishEvent(new ContextRefreshedEvent(this));

2)自己发布事件;

3)容器关闭会发布ContextClosedEvent;

【发布事件】

publishEvent(new ContextRefreshedEvent(this));

1)获取事件的多播器(派发器):getApplicationEventMulticaster()

2)multicastEvent派发事件(原理见下);

3)获取到所有的ApplicationListener【原理见下】;

for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {

3.1)、如果有Executor,可以支持使用Executor进行异步派发;

Executor executor = getTaskExecutor();

3.2)、否则,同步的方式直接执行listener方法;invokeListener(listener,event);拿到listener回调onApplicationEvent方法;

【事件多播器(派发器)】

1.1)容器创建对象:refresh();

1.2)在refresh中调用initApplicationEventMulticaster();初始化applicationEventMulticaster

1.2.1)先去容器中找有没有id=“applicationEventMulticaster”的组件;

1.2.2)如果没有this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);并且加入到容器中,我们就可以在其他组件要派发事件时候,自动注入这个applicationEventMulticaster;

【容器中有哪些监听器】

1)容器创建对象:refresh();

2)registerListeners();从容器中拿到所有的监听器,把他们注册到applicationEventMulticaster中;

String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
//将listener注册到ApplicationEventMulticaster中
   getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);

注解实现监听

@EventListener

//可以写多个
@EventListener(classes={ApplicationEvent.class})
public void listen(ApplicationEvent event){
        System.out.println("UserService监听事件:"+event);
    }

@EventListener原理:
使用EventListenerMethodProcessor处理器来解析方法上的@EventListener;

SmartInitializingSingleton 原理:

1)ioc容器创建对象并refresh();

2)finishBeanFactoryInitialization(beanFactory);调用preInstantiateSingletons,初始化剩下的单实例bean;

2.1)先创建所有的单实例bean;getBean();

//DefaultListableBeanFactory implement ConfigurableListableBeanFactory 
//实现了方法preInstantiateSingletons
for (String beanName : beanNames) {
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                if (isFactoryBean(beanName)) {
                    final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                        isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                            @Override
                            public Boolean run() {
                                return ((SmartFactoryBean<?>) factory).isEagerInit();
                            }
                        }, getAccessControlContext());
                    }
                    else {
                        isEagerInit = (factory instanceof SmartFactoryBean &&
                                ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {
                        getBean(beanName);
                    }
                }
                else {
                    getBean(beanName);
                }
            }
        }

2.2)获取所有创建好的单实例bean,判断是否是SmartInitializingSingleton类型的;如果是就调用afterSingletonsInstantiated();

//DefaultListableBeanFactory implement ConfigurableListableBeanFactory 
//实现了方法preInstantiateSingletons
for (String beanName : beanNames) {
            Object singletonInstance = getSingleton(beanName);
            if (singletonInstance instanceof SmartInitializingSingleton) {
                final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
                if (System.getSecurityManager() != null) {
                    AccessController.doPrivileged(new PrivilegedAction<Object>() {
                        @Override
                        public Object run() {
                            smartSingleton.afterSingletonsInstantiated();
                            return null;
                        }
                    }, getAccessControlContext());
                }
                else {
                    smartSingleton.afterSingletonsInstantiated();
                }
            }
        }

3)调用EventListenerMethodProcessor实现的 SmartInitializingSingleton接口的afterSingletonsInstantiated方法

for (Method method : annotatedMethods.keySet()) {
                    for (EventListenerFactory factory : factories) {
                        if (factory.supportsMethod(method)) {
                            Method methodToUse = AopUtils.selectInvocableMethod(
                                    method, this.applicationContext.getType(beanName));
                            ApplicationListener<?> applicationListener =
                                    factory.createApplicationListener(beanName, targetType, methodToUse);
                            if (applicationListener instanceof ApplicationListenerMethodAdapter) {
                                ((ApplicationListenerMethodAdapter) applicationListener)
                                        .init(this.applicationContext, this.evaluator);
                            }
                            this.applicationContext.addApplicationListener(applicationListener);
                            break;
                        }
                    }



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