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;
}
}
原文地址:https://www.cnblogs.com/ntbww93/p/10104996.html