优势
- 解耦
- 对同一种事件有多种处理方式
- 不干扰主线(main line)
起源
要讲spring的事件通知机制，就要先了解一下spring中的这些接口和抽象类：
ApplicationEventPublisherAware 接口:用来 publish event
ApplicationEvent 抽象类，记录了source和初始化时间戳：用来定义Event
ApplicationListener<E extends ApplicationEvent> :用来监听事件
构建自己的事件机制案例
测试案例
测试入口
package com.meituan.spring.testcase.listener; import org.springframework.context.support.ClassPathXmlApplicationContext; import java.util.concurrent.TimeUnit; /**
* Created by zhangxiaoguang on 16/1/27 下午11:40.
* -----------------------------
* Desc:
*/
public class TestPortal {
public static void main(String[] args) throws InterruptedException { final ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-config.xml"); String[] definitionNames = applicationContext.getBeanDefinitionNames();
System.out.println("==============bean====start=================");
for (String definitionName : definitionNames) {
System.out.println("bean----:" + definitionName);
}
System.out.println("==============bean====end=================");
System.out.println();
final CustomizePublisher customizePublisher = applicationContext.getBean(CustomizePublisher.class); Thread thread = new Thread(new Runnable() {
@Override
public void run() {
try {
System.out.println("开始吃饭："); MealEvent lunchEvent = new MealEvent("A吃午饭了", MealEnum.lunch);
MealEvent breakfastEvent = new MealEvent("B吃早饭了", MealEnum.breakfast);
MealEvent dinnerEvent = new MealEvent("C吃晚饭了", MealEnum.dinner);
customizePublisher.publish(lunchEvent);
TimeUnit.SECONDS.sleep(1l);
customizePublisher.publish(breakfastEvent);
TimeUnit.SECONDS.sleep(1l);
customizePublisher.publish(dinnerEvent);
TimeUnit.SECONDS.sleep(1l); System.out.println("他们吃完了！");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
thread.setName("meal-thread");
thread.start(); System.out.println(Thread.currentThread().getName() + " is waiting for ....");
thread.join();
System.out.println("Done!!!!!!!!!!!!");
}
}
TestPortal
测试结果
测试成员
MealListener ：MealEvent 演员
TroubleListener ：TroubleEvent 演员
AllAcceptedListener 演员
MealEnum 道具
TestPortal 入口
CustomizePublisher 导演
成员代码
接受全部事件的演员（很负责任啊）
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component; /**
* Created by zhangxiaoguang on 16/1/27 下午11:27.
* -----------------------------
* Desc:
*/
@Component
public class AllAcceptedListener implements ApplicationListener<ApplicationEvent> {
@Override
public void onApplicationEvent(ApplicationEvent event) {
System.out.println(">>>>>>>>>>>>>>>>event:" + event);
}
}
AllAcceptedListener
导演负责分发事件
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Component; /**
* Created by zhangxiaoguang on 16/1/28 上午1:41.
* -----------------------------
* Desc:
*/
@Component
public class CustomizePublisher implements ApplicationEventPublisherAware { private ApplicationEventPublisher applicationEventPublisher; public void publish(MealEvent event) {
applicationEventPublisher.publishEvent(event);
} @Override
public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
this.applicationEventPublisher = applicationEventPublisher;
}
}
CustomizePublisher
负责处理吃饭事件的演员
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component; /**
* Created by zhangxiaoguang on 16/1/27 下午11:27.
* -----------------------------
* Desc:
*/
@Component
public class MealListener implements ApplicationListener<MealEvent> {
@Override
public void onApplicationEvent(MealEvent event) {
System.out.println(String.format(">>>>>>>>>>>thread:%s,type:%s,event:%s",
Thread.currentThread().getName(), event.getMealEnum(), event)); dispatchEvent(event);
} private void dispatchEvent(MealEvent event) {
switch (event.getMealEnum()) {
case breakfast:
System.out.println(event.getMealEnum() + " to handle!!!");
break;
case lunch:
System.out.println(event.getMealEnum() + " to handle!!!");
break;
case dinner:
System.out.println(event.getMealEnum() + " to handle!!!");
break;
default:
System.out.println(event.getMealEnum() + " error!!!");
break;
}
}
}
MealListener
吃饭消息
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationEvent; /**
* Created by zhangxiaoguang on 16/1/27 下午11:24.
* -----------------------------
* Desc:吃饭事件
*/
public class MealEvent extends ApplicationEvent { private MealEnum mealEnum; /**
* @param mealContent
* 吃什么
* @param mealEnum
* 早餐还是午餐？
*/
public MealEvent(String mealContent, MealEnum mealEnum) {
super(mealContent);
this.mealEnum = mealEnum;
} public MealEnum getMealEnum() {
return mealEnum;
}
}
MealEvent
工具
package com.meituan.spring.testcase.listener; /**
* Created by zhangxiaoguang on 16/1/27 下午11:29.
* -----------------------------
* Desc:
*/
public enum MealEnum {
breakfast,
lunch,
dinner
}
MealEnum
令人厌烦的演员
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component; /**
* Created by zhangxiaoguang on 16/1/27 下午11:27.
* -----------------------------
* Desc:
*/
@Component
public class TroubleListener implements ApplicationListener<TroubleEvent> {
@Override
public void onApplicationEvent(TroubleEvent event) {
System.out.println(">>>>>>>>>>>>>>>>event:" + event);
}
}
TroubleListener
令人厌烦的事件
package com.meituan.spring.testcase.listener; import org.springframework.context.ApplicationEvent; /**
* Created by zhangxiaoguang on 16/1/27 下午11:24.
* -----------------------------
* Desc:令人厌烦的事件
*/
public class TroubleEvent extends ApplicationEvent {
public TroubleEvent(Object source) {
super(source);
}
}
TroubleEvent
总结
详细定制 event 类型的，则相关定制的listener会处理对应的消息，其他listener不会管闲事；
制定* event 类型的，ApplicationEvent的，则会处理所有的事件。
ApplicationEvent
依赖关系
ContextEvent事件机制简介
ContextRefreshedEvent:当整个ApplicationContext容器初始化完毕或者刷新时触发该事件；
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
...... try { ...... // Last step: publish corresponding event.
finishRefresh();
} catch (BeansException ex) {
......
}
}
}
protected void finishRefresh() {
// Initialize lifecycle processor for this context.
initLifecycleProcessor(); // Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh(); // Publish the final event.
publishEvent(new ContextRefreshedEvent(this)); // Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
ContextClosedEvent:当ApplicationContext doClose时触发该事件,这个时候会销毁所有的单例bean；
@Override
public void registerShutdownHook() {
if (this.shutdownHook == null) {
// No shutdown hook registered yet.
this.shutdownHook = new Thread() {
@Override
public void run() {
doClose();
}
};
Runtime.getRuntime().addShutdownHook(this.shutdownHook);
}
}
@Override
public void close() {
synchronized (this.startupShutdownMonitor) {
doClose();
// If we registered a JVM shutdown hook, we don't need it anymore now:
// We've already explicitly closed the context.
if (this.shutdownHook != null) {
try {
Runtime.getRuntime().removeShutdownHook(this.shutdownHook);
}
catch (IllegalStateException ex) {
// ignore - VM is already shutting down
}
}
}
}
protected void doClose() {
if (this.active.get() && this.closed.compareAndSet(false, true)) {
......
try {
// Publish shutdown event.
publishEvent(new ContextClosedEvent(this));
}
catch (Throwable ex) {
logger.warn("Exception thrown from ApplicationListener handling ContextClosedEvent", ex);
}
......
}
}
ContextStartedEvent:当ApplicationContext start时触发该事件；
@Override
public void start() {
getLifecycleProcessor().start();
publishEvent(new ContextStartedEvent(this));
}
ContextStoppedEvent:当ApplicationContext stop时触发该事件；
@Override
public void stop() {
getLifecycleProcessor().stop();
publishEvent(new ContextStoppedEvent(this));
}
ApplicationListener
依赖关系
带你一步步走向源码的世界
从上边打印的线程信息可以知道，spring处理事件通知采用的是当前线程，并没有为为我们启动新的线程，所以，如果需要，你要自己处理线程信息哦，当然也可以设定（如何设置？）！
AbstractApplicationContext
补齐：同一个event，被多个listener监听，先被哪个listener执行是由下边的代码决定的：
如何设置线程池？
回到上边的问题，到底该如何设置线程池呢？
AbstractApplicationEventMulticaster 是private的，并且没有提供写入方法...
实际案例
用在自己的代码里就是最好的例子了 ^_^