servlet context listener

ServletContextListener

@WebListener
public class ServletContextListenerDemo implements ServletContextListener{

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {

    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

ServletContextAttributeListener

@WebListener
public 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。