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一、HttpSession对象的生命周期监听器
HttpSessionListener接口定义了HttpSession对象生命周期的监听行为。
void sessionCreated(HttpSessionEvent se)
HttpSession对象创建后会触发该监听器方法，并将已创建HttpSession对象传递到该方法中
void sessionDestoryed(HttpSessionEvent se)
HttpSession对象在销毁之前会触发该监听方法，并将要销毁的HttpSession对象传递到该方法中
二、创建能够监听HttpSession生命周期的监听器
web.xml
<listener><listener-class>cn.itcast.listener.HttpSessiontLifecycleListener</listener-class></listener>实现类:
package cn.itcast.listener;import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;public class HttpSessiontLifecycleListener implements HttpSessionListener {/*监听HttpSession 对象创建的监听方法*/@Overridepublic void sessionCreated(HttpSessionEvent se) {System.out.println("sessionCreated");System.out.println(se.getSession());}/*监听HttpSession 对象创建的监听方法*/@Overridepublic void sessionDestroyed(HttpSessionEvent se) {System.out.println("sessionDestroyed");System.out.println(se.getSession());}
}
三、HttpSession对象的属性操作监听器
HttpSessionAttributeListener接口定义了对于HttpSession对象属性操作的监听行为。
void attributeAdded(HttpSessionBindingEvent se)
HttpSession对象中添加属性是会触发该监听方法，并将HttpSession对象传递到该方法中，触发事件的方法HttpSession.setAttribute("key","value")
void attributeRemove(HttpSessionBindingEvent se)
HttpSession对象中添加属性是会触发该监听方法，并将HttpSession对象传递到该方法中，触发事件的方法HttpSession.removeAttribute("key","value")
void attributeReplaced(HttpSessionBindingEvent se)
HttpSession对象中添加属性是会触发该监听方法，并将HttpSession对象传递到该方法中，触发事件的方法HttpSession.setAttribute("key","value")
实例代码:
servlet:
package cn.itcast.listener;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;/*** 测试HttpSession属性监听器*/
@WebServlet("/sessionAttr.do")
public class HttpSessionAttrServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取httpSession对象HttpSession httpSession = req.getSession();httpSession.setAttribute("key","test");httpSession.setAttribute("key","test2");httpSession.removeAttribute("key");}
}
监听:
package cn.itcast.listener;import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;public class HttpSessionAttrListener implements HttpSessionAttributeListener {@Overridepublic void attributeAdded(HttpSessionBindingEvent se) {System.out.println("-------HttpSession---Start attributeAdded----------");System.out.println("Name:"+se.getName()+" Value:"+se.getValue());System.out.println("-------HttpSession---End attributeAdded----------");}@Overridepublic void attributeRemoved(HttpSessionBindingEvent se) {System.out.println("-------HttpSession---Start attributeRemoved----------");System.out.println("Name:"+se.getName()+" Value:"+se.getValue());System.out.println("-------HttpSession---End attributeRemoved----------");}@Overridepublic void attributeReplaced(HttpSessionBindingEvent se) {System.out.println("-------HttpSession---Start attributeReplaced----------");System.out.println("Name:"+se.getName()+" Value:"+se.getValue());System.out.println("-------HttpSession---End attributeReplaced----------");}
}
输出结果:
-------HttpSession---Start attributeAdded----------
Name:key Value:test
-------HttpSession---End attributeAdded-----------------HttpSession---Start attributeReplaced----------
Name:key Value:test
-------HttpSession---End attributeReplaced-----------------HttpSession---Stary attributeRemoved----------
Name:key Value:test2
-------HttpSession---End attributeRemoved----------
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