Spring筆記Spring Event

Spring中提供一些Aware相關的介面，BeanFactoryAware、 ApplicationContextAware、ResourceLoaderAware、ServletContextAware等等，其中最常用到的是ApplicationContextAware。實現ApplicationContextAware的Bean，在Bean被初始後，將會被注入 ApplicationContext的執行個體。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：

 

  public class MessageEvent extends ApplicationEvent {
       /**
       * 
       */
      private static final long serialVersionUID = 1L;
      private String msg;
          public MessageEvent(Object source, String msg) {
              super(source);
              this.msg = msg;
         }
         
         public String getMessage() {
             return msg;
         }
 }

 

 

 

 

 

  public class Publisher implements ApplicationContextAware {
  
       private ApplicationContext ctx;
  
          public void setApplicationContext(ApplicationContext applicationContext)
                  throws BeansException {
              this.ctx = applicationContext;
  
          }
 
         public void publish(String message) {
             ctx.publishEvent(new MessageEvent(this, message));
         }
         
         public static void main(String[] args) {
             ApplicationContext ctx = new FileSystemXmlApplicationContext(
                     "src/applicationContext.xml");
 
             Publisher pub = (Publisher) ctx.getBean("publisher");
             pub.publish("Hello World!");
             pub.publish("The quick brown fox jumped over the lazy dog");
         }
 
}

 

 

 public class MessageEventListener implements ApplicationListener {
 
       public void onApplicationEvent(ApplicationEvent event) {
            if(event instanceof MessageEvent) {
                MessageEvent msgEvt = (MessageEvent)event;
                System.out.println("Received: " + msgEvt.getMessage());
            }
         }
 }

 

 

在運行期，ApplicationContext會自動在當前的所有Bean中尋找ApplicationListener介面的實現，並將其作為事件接收對象。當Application.publishEvent方法調用時，所有的ApplicationListener介面實現都會被激發，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。

定義Event類，繼承org.springframework.context.ApplicationEvent.

編寫發布事件類別Publisher，實現org.springframework.context.ApplicationContextAware介面.

覆蓋方法setApplicationContext(ApplicationContext applicationContext)和發布方法publish(Object obj)

定義時間監聽類EventListener，實現ApplicationListener介面，實現方法onApplicationEvent(ApplicationEvent event).

 

本文轉自:http://blog.csdn.net/jiqimiao/archive/2007/09/25/1799991.aspx