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//事件涉及的三个组件:事件源、事件对象、事件监听器
//一个总的事件监听器接口，所有不同分类的事件监听器都继承这个接口
public interface EventListener {
}
//例如 ServletContextListener 这个ServletContext监听器 他有两个方法，一个是初始化方法，另一个是销毁的方法。在web.xml中配置了listener，那么容器在启动时就会扫描web.xml的listener的配置，自动调用contextInitialized 方法，在容器重启时，他会先调用contextDestroyed销毁的方法，在调用contextInitialized 创建的方法。在容器关闭时，会调用contextDestroyed方法。但我刚启动完容器，立刻关闭，是不会调用到contextDestroyed方法的。我想他这里应该有设置时间的吧。
public interface ServletContextListener extends EventListener { /** ** Notification that the web application initialization ** process is starting. ** All ServletContextListeners are notified of context ** initialization before any filter or servlet in the web ** application is initialized. */ public void contextInitialized ( ServletContextEvent sce ); //接受的参数是ServletContextEvent 事件源 /** ** Notification that the servlet context is about to be shut down. ** All servlets and filters have been destroy()ed before any ** ServletContextListeners are notified of context ** destruction. */
public void contextDestroyed ( ServletContextEvent sce ); }
//每一个事件对象都有一个总的事件对象类，下面这个就是了。
public class EventObject implements java.io.Serializable { private static final long serialVersionUID = 5516075349620653480L; /** * The object on which the Event initially occurred. */ protected transient Object source; /** * Constructs a prototypical Event. * * @param source The object on which the Event initially occurred. * @exception IllegalArgumentException if source is null. */ public EventObject(Object source) { if (source == null) throw new IllegalArgumentException("null source"); //在这里封装一个事件源 this.source = source; } /** * The object on which the Event initially occurred. * * @return The object on which the Event initially occurred. */ public Object getSource() { return source; //得到事件源 } /** * Returns a String representation of this EventObject. * * @return A a String representation of this EventObject. */ public String toString() { return getClass().getName() + "[source=" + source + "]"; } }
public class ServletContextEvent extends java.util.EventObject { /** Construct a ServletContextEvent from the given context. * * @param source - the ServletContext that is sending the event. */ public ServletContextEvent(ServletContext source) { super(source); } /** * Return the ServletContext that changed. * * @return the ServletContext that sent the event. */ public ServletContext getServletContext () { return (ServletContext) super.getSource();//返回一个真正的事件源 } }
这就是tomcat的事件监听设计模型。
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原文地址：http://www.cnblogs.com/hjy9420/p/4215561.html
