Spring源码解析-事件
Spring事件的组件
主要是3个组件：
1.ApplicationEvent 事件
2.ApplicationListener 监听器,对事件进行监听
3.ApplicationEventMulticaster 事件广播器，将publish的事件广播给所有的监听器。
事件
ContextRefreshedEvent :当ApplicationContext初始化或者刷新，将会发布，例如使用ConfigurableApplicationContext接口调用refresh方法，初始化意味着加载所有的bean，同时
ApplicationContext是支持热刷新。
ContextStartedEvent：当ApplicationContext启动的时候，将会调用start方法，发布此事件。
ContextStoppedEvent：当容器停止的时候，发布事件。
ContextClosedEvent：当容器关闭的时候，发布事件。
RequestHandledEvent：http请求完成后，发布事件。
监听器
ApplicationListener：ApplicationContext容器内部自定义事件监听器接口，继承自java.util.EventListener,ApplicationContext容器在启动时，会自动识别并加载EventListener类型bean的定义，一旦容器事件发布，将会通知注册到容器的监听器。
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
/**
* Handle an application event.
* @param event the event to respond to
*/
void onApplicationEvent(E event);
}
发布事件者
ApplicationEventPublisher和ApplicationEventMulticaster
ApplicationEventPublisher：是一个封装事件发布接口，作为ApplicationContext父类接口。
ApplicationEventMulticaster：管理ApplicationListener对象，并且发布它们。
ApplicationContext继承ApplicationEventPublisher而担当者事件发布的角色，而ApplicationContext并没有进行事件的发布，而是交给了AbstractApplicationEventMulticaster来实现事件监听器的管理。
简单实例
模拟人民银行利息调整，通知到其他银行的事件。
利息事件
package org.lzyer.test;
import org.springframework.context.ApplicationEvent;
/**
* Created by Administrator on 2017/10/23.
*/
public class ExRateChangeEvent extends ApplicationEvent {
/**
* Create a new ApplicationEvent.
*
* @param source the component that published the event (never {@code null})
*/
public ExRateChangeEvent(Object source) {
super(source);
}
}
农业银行监听器
package org.lzyer.test;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;
/**
* Created by Administrator on 2017/10/23.
*/
@Component
public class ABCListener implements ApplicationListener<ApplicationEvent> {
@Override
public void onApplicationEvent(ApplicationEvent event) {
if(event instanceof ExRateChangeEvent){
System.out.println("农业银行收到->"+event.getSource());
}
}
}
工商银行监听器
package org.lzyer.test;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;
/**
* Created by Administrator on 2017/10/23.
*/
@Component
public class ICBCListener implements ApplicationListener<ApplicationEvent> {
@Override
public void onApplicationEvent(ApplicationEvent event) {
if(event instanceof ExRateChangeEvent){
System.out.println("工商银行收到->"+event.getSource());
}
}
}
spring-beans.xml配置文件
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="org.lzyer.test"></context:component-scan>
</beans>
测试代码
@Test
public void testPublishEvent(){
ApplicationContext context = new ClassPathXmlApplicationContext("spring/spring-beans.xml");
context.publishEvent(new ExRateChangeEvent("利息上调"));
}
结果：
农业银行收到->利息上调
工商银行收到:->利息上调
事件原理流程
spring容器初始化调用的refresh方法
AbstractApplicationContext@refresh
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//省略
try {
//省略
// 初始化广播事件
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
//注册监听器
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
//省略
}
}
}
initApplicationEventMulticaster()注册广播事件
protected void initApplicationEventMulticaster() {
//获取beanFactory
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isDebugEnabled()) {
logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {//创建一个默认的事件广播器
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
"': using default [" + this.applicationEventMulticaster + "]");
}
}
}
AbstractApplicationEventMulticaster类中的属性
registerListeners方法
/**
* Add beans that implement ApplicationListener as listeners.
* Doesn't affect other listeners, which can be added without being beans.
*/
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 lisName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(lisName);
}
}
在refresh最后的一个方法，中发布刷新事件。
finishRefresh
protected void finishRefresh() {
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.发布刷新事件
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
事件整体结构图
最后走一波debug
参考资料
http://www.jianshu.com/p/bc1055b065ce
http://liuxiamai.iteye.com/blog/2322197
http://jinnianshilongnian.iteye.com/blog/1902886
