servlet context listener

ServletContextListener

@WebListenerpublic class ServletContextListenerDemo implements ServletContextListener{    @Override    public void contextInitialized(ServletContextEvent servletContextEvent) {    }    @Override    public void contextDestroyed(ServletContextEvent servletContextEvent) {    }}

ServletContextAttributeListener

@WebListenerpublic class ServletContextAttributeListenerDemo implements ServletContextAttributeListener {    @Override    public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {    }    @Override    public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {    }    @Override    public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {    }}

说明：servletContext上下文监听器，是整个应用在启动的时候加载的context.一个web application只会有一个context.因此，servletContext是对整个appliction全程有效的。