HttpSessionListener-創建與銷燬
//@WebListener servlet3.0支持註解
public class HttpSessionListenerDemo implements HttpSessionListener{
@Override
public void sessionCreated(HttpSessionEvent httpSessionEvent) {
HttpSession session = httpSessionEvent.getSession();
ServletContext servletContext = session.getServletContext();
// undo
}
@Override
public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
// undo
}
}
HttpSessionActivationListener-頓化與激活
//@WebListener servlet3.0支持註解
public class HttpSessionActivationListenerDemo implements HttpSessionActivationListener {
@Override
public void sessionWillPassivate(HttpSessionEvent httpSessionEvent) {
}
@Override
public void sessionDidActivate(HttpSessionEvent httpSessionEvent) {
}
}
HttpSessionAttributeListener-屬性值變化
//@WebListener servlet3.0支持註解
public class HttpSessionAttributeListenerDemo implements HttpSessionAttributeListener {
@Override
public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
}
@Override
public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
}
@Override
public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
}
}
HttpSessionBindingListener-屬性值刪除或增加
//@WebListener servlet3.0支持註解
public class HttpSessionBindingListenerDemo implements HttpSessionBindingListener {
@Override
public void valueBound(HttpSessionBindingEvent httpSessionBindingEvent) {
}
@Override
public void valueUnbound(HttpSessionBindingEvent httpSessionBindingEvent) {
}
}
設計架構
監聽器的設計模式是觀察者模式。
事件源:HttpSession
事件:EventObject的子類,如:HttpSessionEvent和HttpSessionBindingEvent
事件監聽器:EventListener的子類。
被觀察者是servlet容器。觀察者則是我們寫的listener.通常在自已實現的listener中都會引入實際的觀察者,來處理事件。
說明:web.xml的加載順序是:【Context-Param】->【Listener】->【Filter】->【Servlet】,而同個類型之間的實際程序調用的時候的順序是根據對應的Mapping的順序進行調用。