HttpSessionListener、ServletContextListener、ServletRequestListener分别用于控制Session、context、request的创建和销毁。触发时机分别为:
- HttpSessionListener:监听Session的创建和销毁。创建session时执行sessionCreated(HttpSessionEvent se)方法。超时或者执行session.invalidate()时执行sessionDestroyed(HttpSessionEvent se)方法。该Listener用于收集在线者信息。
- ServletContextListener:监听context的创建和销毁。context代表当前的web应用程序。服务器启动或者热部署war包时执行contextInitialized(ServletContextEvent event)方法。服务器关闭或者只关闭该web时会执行contextDestoryed(ServletContextEvent event)方法。该Listener可用于获取web.xml里配置的初始化参数。
- ServletRequestListener:监听request的创建和销毁。用户每次请求request都会执行requestInitialized(ServletRequestEvent event)方法。request处理完毕自动销毁前执行requestDestoryed(ServletRequestEvent event)方法。如果一个HTML页面内含有多个图片,则请求一次HTML页面可能会出发多次request事件。
package linstener; import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory; public class LinstenerTest implements HttpSessionListener, ServletContextListener, ServletRequestListener { private Log log =LogFactory.getLog(this.getClass());
@Override
public void requestDestroyed(ServletRequestEvent arg0) {
//销毁Request时调用
HttpServletRequest request=(HttpServletRequest)arg0.getServletRequest();
long time=System.currentTimeMillis()-(long)request.getAttribute("dateCreated");
log.info(request.getRemoteAddr()+"请求处理结束,用时"+time+"毫秒。");
} @Override
public void requestInitialized(ServletRequestEvent arg0) { //创建Request时调用
HttpServletRequest request=(HttpServletRequest) arg0.getServletRequest();
String uri=request.getRequestURI();
uri=request.getQueryString()==null?uri:(uri+"?"+request.getQueryString());
request.setAttribute("dateCreated", System.currentTimeMillis());
log.info("IP:"+request.getRemoteAddr()+" 请求 "+uri);
} @Override
public void contextDestroyed(ServletContextEvent arg0) {
//销毁Servlet上下文时调用
ServletContext servletContext=arg0.getServletContext();
log.info("即将关闭"+servletContext.getContextPath());
} @Override
public void contextInitialized(ServletContextEvent arg0) {
//加载Servlet上下文时调用
ServletContext servletContext=arg0.getServletContext();
log.info("即将启动"+servletContext.getContextPath());
} @Override
public void sessionCreated(HttpSessionEvent arg0) {
//创建session时调用
HttpSession session =arg0.getSession();
log.info("新创建一个session,ID为:"+session.getId());
} @Override
public void sessionDestroyed(HttpSessionEvent arg0) {
//销毁session前调用
HttpSession session =arg0.getSession();
log.info("销毁一个session,ID为:"+session.getId());
} }
Listener类web.xml文件中的配置:
<listener>
<listener-class>
linstener.LinstenerTest
</listener-class>
</listener>