Listener监听器----HttpSession对象的生命周期监听器

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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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