Servlet、Listener、Filter与容器与容器之间的关系
1.Listener项目上下文是从event中获取的。Listener通过event与容器发生关系。
public interface ServletContextListener extends EventListener{public void contextInitialized ( ServletContextEvent sce );ServletContext servletContext;public void contextInitialized(ServletContextEvent sce){servletContext = sce.getServletContext();}}