ServletContextListener、MyHttpSessionListener、ServletContextAttributeListener、对象绑定解绑、文件钝化活化

来源：互联网发布：离线下载知乎编辑：程序博客网时间：2024/04/29 05:22

ServletContextListener创建、销毁

配置文件配置入下：

   <listener>    <listener-class>com.itheima.create.MyServletContextListener</listener-class>  </listener>

package com.itheima.create;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Timer;import java.util.TimerTask;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;public class MyServletContextListener implements ServletContextListener{    @Override    //监听context域对象的创建    public void contextInitialized(ServletContextEvent sce) {        //就是被监听的对象---ServletContext        ServletContext servletContext = sce.getServletContext();        //getSource就是被监听的对象  是通用的方法        ServletContext source = (ServletContext) sce.getSource();        System.out.println("context创建了....");        //开启一个计息任务调度----每天晚上12点 计息一次        Timer timer = new Timer();        //task:任务  firstTime：第一次执行时间  period：间隔执行时间//      timer.scheduleAtFixedRate(task, firstTime, period);        timer.scheduleAtFixedRate(new TimerTask() {            @Override            public void run() {                System.out.println("银行计息了.....");            }        } , new Date(), 5000);}    //监听context域对象的销毁    @Override    public void contextDestroyed(ServletContextEvent sce) {        System.out.println("context销毁了....");    }}

发布项目输出：context创建了….
定时器输出：银行计息了…..
停止服务器：context销毁了….

MyHttpSessionListener创建、销毁

我们访问一个jsp页面，因为session是jsp页面的内置对象，所以第一次访问时候，默认创建session
首先需要配置如下：

 <listener>    <listener-class>com.itheima.create.MyHttpSessionListener</listener-class>  </listener>

session.jsp

<body>    xxxxxxxxxxxxxxxxxxxxxx</body>

package com.itheima.create;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;public class MyHttpSessionListener implements HttpSessionListener{    @Override    public void sessionCreated(HttpSessionEvent se) {        System.out.println("session创建"+se.getSession().getId());    }    @Override    public void sessionDestroyed(HttpSessionEvent se) {        System.out.println("session销毁");    }}

访问http://localhost:8080/WEB23/session.jsp
控制台输出：
session创建26F54F5E56E2EFB501DBE76A751C82DC

ServletContextAttributeListener修改、删除、添加

配置如下：

   <listener>    <listener-class>com.itheima.attribute.MyServletContextAttributeListener</listener-class>  </listener>

package com.itheima.attribute;import javax.servlet.ServletContextAttributeEvent;import javax.servlet.ServletContextAttributeListener;public class MyServletContextAttributeListener implements ServletContextAttributeListener{    @Override    public void attributeAdded(ServletContextAttributeEvent scab) {        //放到域中的属性        System.out.println(scab.getName());//放到域中的name        System.out.println(scab.getValue());//放到域中的value    }    @Override    public void attributeRemoved(ServletContextAttributeEvent scab) {        System.out.println(scab.getName());//删除的域中的name        System.out.println(scab.getValue());//删除的域中的value    }    @Override    public void attributeReplaced(ServletContextAttributeEvent scab) {        System.out.println(scab.getName());//获得修改前的name        System.out.println(scab.getValue());//获得修改前的value    }}

看看servlet代码如下：

package com.itheima.attribute;import java.io.IOException;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestMyServletContextAttributeListener extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        ServletContext context = this.getServletContext();        //向context域中存数据        context.setAttribute("name", "tom");        //改context数据        context.setAttribute("name", "lucy");        //删除context数据        context.removeAttribute("name");    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

页面输入：http://localhost:8080/WEB23/test1
输出如下：

nametomnametomnamelucy

HttpSessionBindingListener绑定对象

绑定监听器无需再web.xml中进行配置

package com.itheima.domian;import javax.servlet.http.HttpSessionBindingEvent;import javax.servlet.http.HttpSessionBindingListener;public class Person implements HttpSessionBindingListener{    private String id;    private String name;    public String getId() {        return id;    }    public void setId(String id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    //绑定的方法    public void valueBound(HttpSessionBindingEvent event) {        System.out.println("person被绑定了");    }    @Override    //解绑方法    public void valueUnbound(HttpSessionBindingEvent event) {        System.out.println("person被解绑了");    }}

package com.itheima.domian;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class TestPersonBindingServlet extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        HttpSession session = request.getSession();        //将person对象绑到session中        Person p = new Person();        p.setId("100");        p.setName("zhangsanfeng");        session.setAttribute("person", p);        //将person对象从session中解绑        session.removeAttribute("person");    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

浏览器输入：http://localhost:8080/WEB23/testBinding
输出如下：

person被绑定了person被解绑了

HttpSessionActivationListener钝化、活化

package com.itheima.domian;import java.io.Serializable;import javax.servlet.http.HttpSessionActivationListener;import javax.servlet.http.HttpSessionEvent;public class Customer implements HttpSessionActivationListener,Serializable{    private String id;    private String name;    public String getId() {        return id;    }    public void setId(String id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    //钝化    public void sessionWillPassivate(HttpSessionEvent se) {        System.out.println("customer被钝化了");    }    @Override    //活化    public void sessionDidActivate(HttpSessionEvent se) {        System.out.println("customer被活化了");    }}

package com.itheima.domian;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class TestCustomerActiveServlet extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        HttpSession session = request.getSession();        //将customer放到session中        Customer customer =new Customer();        customer.setId("200");        customer.setName("lucy");        session.setAttribute("customer", customer);        System.out.println("customer被放到session域中了");    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

package com.itheima.domian;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class TestCustomerActiveServlet2 extends HttpServlet {    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        //从session域中获得customer        HttpSession session = request.getSession();        Customer customer = (Customer) session.getAttribute("customer");        System.out.println(customer.getName());    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

http://localhost:8080/WEB23/testActive
然后停止服务器，使其出现钝化状态
然后在启动服务器，使其活化

我们可以在如下的文件中进行配置
这里写图片描述

<?xml version="1.0" encoding="UTF-8"?><Context>    <!-- maxIdleSwap:session中的对象多长时间不使用就钝化 -->    <!-- directory:钝化后的对象的文件写到磁盘的哪个目录下 配置钝化的对象文件在 work/catalina/localhost/钝化文件 -->    <Manager className="org.apache.catalina.session.PersistentManager" maxIdleSwap="1">        <Store className="org.apache.catalina.session.FileStore" directory="itheima32" />    </Manager></Context>

钝化的文件保存在下面：
这里写图片描述

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