Spring
中提供一些Aware相關的接口，BeanFactoryAware、 ApplicationContextAware、ResourceLoaderAware、ServletContextAware等等，其中最常用到的是ApplicationContextAware。實現ApplicationContextAware的Bean，在Bean被初始后，將會被注入 ApplicationContext的實例。ApplicationContextAware
提供了publishEvent()方法，實現Observer(觀察者)設計模式的事件傳播機
，提供了針對Bean的事件傳播功能。通過Application.publishEvent方法，我們可以將事件通知系統內所有的ApplicationListener。
Spring事件處理一般過程：
定義Event類，繼承org.springframework.context.ApplicationEvent.
編寫發布事件類Publisher，實現org.springframework.context.ApplicationContextAware接口.
覆蓋方法
setApplicationContext ( ApplicationContext?applicationContext )和發布方法
定義時間監聽類
EventListener，實現
ApplicationListener接口，實現方法
onApplicationEvent ( ApplicationEvent?event ).
?1?public?class?MessageEvent?extends
?ApplicationEvent?{
?2??????/**
?3?
?????*?
?4??????*/
?5?????private?static?final?long?serialVersionUID?=?1L
;
?6?????private
?String?msg;
?7?????????public
?MessageEvent(Object?source,?String?msg)?{
?8?????????????super
(source);
?9?????????????this.msg?=
?msg;
10?
????????}
11?
????????
12?????????public
?String?getMessage()?{
13?????????????return
?msg;
14?
????????}
15?
}
?1
?public?class?Publisher?implements
?ApplicationContextAware?{
?2?
?3??????private
?ApplicationContext?ctx;
?4?
?5?????????public?void
?setApplicationContext(ApplicationContext?applicationContext)
?6?????????????????throws
?BeansException?{
?7?????????????this.ctx?=
?applicationContext;
?8?
?9?
????????}
10?
11?????????public?void
?publish(String?message)?{
12?????????????ctx.publishEvent(new?MessageEvent(this
,?message));
13?
????????}
14?
????????
15?????????public?static?void
?main(String[]?args)?{
16?????????????ApplicationContext?ctx?=?new
?FileSystemXmlApplicationContext(
17?????????????????????"src/applicationContext.xml"
);
18?
19?????????????Publisher?pub?=?(Publisher)?ctx.getBean("publisher"
);
20?????????????pub.publish("Hello?World!"
);
21?????????????pub.publish("The?quick?brown?fox?jumped?over?the?lazy?dog"
);
22?
????????}
23?
24?}
1?public?class?MessageEventListener?implements
?ApplicationListener?{
2?
3???????public?void
?onApplicationEvent(ApplicationEvent?event)?{
4????????????if(event?instanceof
?MessageEvent)?{
5????????????????MessageEvent?msgEvt?=
?(MessageEvent)event;
6????????????????System.out.println("Received:?"?+
?msgEvt.getMessage());
7?
???????????}
8?
????????}
9?}
1?<beans>
2?????<bean?id="publisher"?class="Publisher"/>
3?????????<bean?id="messageEventListener"?class="MessageEventListener"/>
4?</beans>
在運行期，ApplicationContext會自動在當前的所有Bean中尋找ApplicationListener接口的實現，并將其作為事件接收對象。當Application.publishEvent方法調用時，所有的ApplicationListener接口實現都會被激發，每個ApplicationListener可根據事件的類型判斷是否是自己需要處理的事件，如上面的ActionListener只處理ActionEvent事件。
?
鳳凰涅槃/浴火重生/馬不停蹄/只爭朝夕
???? 隱姓埋名/低調華麗/簡單生活/完美人生