JavaWeb——Listener（监听器）

程序员文章站 2022-06-18 11:16:36

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1、什么是监听器

监听器就是监听某个对象的的状态变化的组件。
监听器的相关概念：
事件源：被监听的对象 —– 三个域对象 request session servletContext
监听器：监听事件源对象事件源对象的状态的变化都会触发监听器 —- 6+2
注册监听器：将监听器与事件源进行绑定
响应行为：监听器监听到事件源的状态变化时所涉及的功能代码 —- 程序员编写代码

2、8个监听器
第一维度：按照被监听的对象划分：ServletRequest域 HttpSession域 ServletContext域
JavaWeb——Listener（监听器）

第二维度：监听的内容分：监听域对象的创建与销毁的监听域对象的属性变化的
1、绑定与解绑的监听器HttpSessionBindingListener
2、钝化与活化的监听器HttpSessionActivationListener

3、监听器对象

3.1 域对象（以ServletContextListener为例）

Servlet域的生命周期
何时创建：服务器启动创建
何时销毁：服务器关闭销毁

创建ServletContextListener监听器

package cn.ctgu.create;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class MyServletContextListener implements ServletContextListener{

    @Override
    //监听context域对象的创建
    public void contextInitialized(ServletContextEvent sc) {
        // TODO Auto-generated method stub
    /*  //就是被监听的对象————ServletContext
        ServletContext servletContext=sc.getServletContext();
        System.out.println("context创建了...");*/

        /*//getSource就是被监听的对象，是通用的方法
        Object source=sc.getSource();*/

        //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() {
                // TODO Auto-generated method stub
                System.out.println("银行计息了。。。。。。");
            }

        }, new Date(), 5000);*/
        //改成银行真正计息
        /*1、起始时间：定义成晚上12点
         * 2、间隔时间：24小时
         * 
         * */
        //设置第一次计息时间为晚上十二点
        SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        String currentTime="2018-04-04 00:00:00";
        Date parse=null;
        try {
            parse=format.parse(currentTime);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        timer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                        // TODO Auto-generated method stub
                    System.out.println("银行计息了。。。。。。");
            }

            }, parse, 24*3600*1000);
    }

    @Override
    //监听context域对象的销毁
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub

    }

}

ServletContextListener监听器的主要作用
a、初始化的工作：初始化对象初始化数据 —- 加载数据库驱动连接池的初始化
b、加载一些初始化的配置文件 — spring的配置文件
c、任务调度—-定时器—-Timer/TimerTask

3.2 HttpSessionListener

HttpSession对象的生命周期:
何时创建：第一次调用request.getSession时创建
何时销毁：服务器关闭销毁 session过期手动销毁

package cn.ctgu.create;

import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

@WebListener
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 arg0) {
        // TODO Auto-generated method stub

    }

}

3.3 ServletRequestListener
ServletRequest的生命周期
创建：每一次请求都会创建request
销毁：请求结束
JavaWeb——Listener（监听器）

3.4 监听三大域对象的属性变化的监听器

域对象的通用的方法：
setAttribute(name,value)
— 触发添加属性的监听器的方法
— 触发修改属性的监听器的方法
getAttribute(name)
removeAttribute(name)
— 触发删除属性的监听器的方法
JavaWeb——Listener（监听器）

package cn.ctgu.attribute.create;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class TestServletContexAttributeListener
*/
@WebServlet(“/TestServletContexAttributeListener”)
public class TestServletContexAttributeListener extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
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");
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    doGet(request, response);
}

}


package cn.ctgu.attribute.create;

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class MyServletContextAttributeListener implements ServletContextAttributeListener{

    @Override
    public void attributeAdded(ServletContextAttributeEvent sc) {
        //放到域中的属性
        System.out.println(sc.getName());//放到域中的name
        System.out.println(sc.getValue());//放到域中的value

    }

    @Override
    public void attributeRemoved(ServletContextAttributeEvent sc) {
        System.out.println(sc.getName());//删除域中的name
        System.out.println(sc.getValue());//删除域中的value
    }

    @Override
    public void attributeReplaced(ServletContextAttributeEvent sc) {
        System.out.println(sc.getName());//获得修改前的域中的name
        System.out.println(sc.getValue());//获得修改前的域中的value
    }

}

HttpSessionAttributeListener监听器、ServletRequestAriibuteListenr监听器（同上）
3.5 与session中的绑定的对象相关的监听器（对象感知监听器）
即将要被绑定到session中的对象有几种状态
绑定与解绑的监听器HttpSessionBindingListener：
绑定状态：就一个对象被放到session域中
解绑状态：就是这个对象从session域中移除了

钝化与活化的监听器HttpSessionActivationListener：
钝化状态：是将session内存中的对象持久化（序列化）到磁盘
活化状态：就是将磁盘上的对象再次恢复到session内存中

3.5.1 HttpSessionBindingListener

被绑定对象Person类：
Person.java

package cn.ctgu.attribute.domain;

import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

public class Person implements HttpSessionBindingListener{
    private String name;
    private int id;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }

    //绑定方法，session将person对象添加的时候触发
    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        // TODO Auto-generated method stub
        System.out.println("person被绑定了");
    }
    //解绑方法,session将person移除掉的时候触发
    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
        // TODO Auto-generated method stub
        System.out.println("person被解绑了");
    }


}

TestPersonBindingServlet.java

package cn.ctgu.attribute.domain;

import java.io.IOException;
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;

/**
 * Servlet implementation class TestPersonBindingServlet
 */
@WebServlet("/TestPersonBindingServlet")
public class TestPersonBindingServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session=request.getSession();
        //将person对象绑定到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");

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

3.5.2 HttpSessionActivationListener

被钝化和活化的Customer类
Customer.java

package cn.ctgu.attribute.domain;

import java.io.Serializable;

import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionEvent;
//实现了Serializable接口才能被活化（序列化）
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;
    }
    //活化
    @Override
    public void sessionDidActivate(HttpSessionEvent arg0) {
        // TODO Auto-generated method stub
        System.out.println("Customer被活化了");
    }
    //钝化
    @Override
    public void sessionWillPassivate(HttpSessionEvent arg0) {
        // TODO Auto-generated method stub
        System.out.println("Customer被钝化了");
    }

}

META-INF目录下的context.xml文件配置钝化路径以及钝化间隔时间

<?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"><!--这里的1表示1分钟，即session 1分钟不用的时候对象就会被钝化到磁盘  -->
        <Store className="org.apache.catalina.session.FileStore"
            directory="C:\Users\Administrator\Desktop\Java\JavaWeb\Listener\SessionActivation" />
    <!--这里的directory表示session钝化后的存储路径  -->
    </Manager>
</Context>

TestCustomerHttpSessionActivationListener.java

package cn.ctgu.attribute.domain;

import java.io.IOException;
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;

/**
 * Servlet implementation class TestCustomerHttpSessionActivationListener
 */
@WebServlet("/TestCustomerHttpSessionActivationListener")
public class TestCustomerHttpSessionActivationListener extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session=request.getSession();
        //将customer放到session中，当服务器关闭的时候customer对象就会被钝化到磁盘中
        Customer customer=new Customer();
        customer.setId("200");
        customer.setName("lucy");
        session.setAttribute("customer", customer);
        System.out.println("customer被放到session域中");
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

TestCustomerHttpSessionActivationListener2.java

package cn.ctgu.attribute.domain;

import java.io.IOException;
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;

/**
 * Servlet implementation class TestCustomerHttpSessionActivationListener2
 */
@WebServlet("/TestCustomerHttpSessionActivationListener2")
public class TestCustomerHttpSessionActivationListener2 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从session域中获得customer,只有服务器重启的时候，session域中的被钝化的对象，才能从磁盘中活化过来被使用
        HttpSession session=request.getSession();
        Customer customer=(Customer)session.getAttribute("customer");
        System.out.println(customer.getName());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

4、邮箱服务器
1．邮箱服务器的基本概念
邮件的客户端：可以只安装在电脑上的也可以是网页形式的
邮件服务器：起到邮件的接受与推送的作用
邮件发送的协议：
协议：就是数据传输的约束
接受邮件的协议：POP3 IMAP
发送邮件的协议：SMTP
JavaWeb——Listener（监听器）
2．邮箱的发送过程

5、案例——定时发送生日祝福邮件

Customers.java

package cn.ctgu.birthday;

public class Customers {
    private int id;
    private String username;
    private String password;
    private String realname;
    private String birthday;
    private String email;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getRealname() {
        return realname;
    }
    public void setRealname(String realname) {
        this.realname = realname;
    }
    public String getBirthday() {
        return birthday;
    }
    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }

}

JDBCUtilsConfig.java

package cn.ctgu.dao;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

/*
 * 编写JDBC的工具类，获取数据库的连接对象采用
 * 采用读取配置文件的方式
 * 读取文件获取连接，执行一次，采用static代码块，
 * 
 * */
public class JDBCUtilsConfig {
    private static Connection con;
    private static String driverClass;
    private static String url;
    private static String username;
    private static String password;
    static {
        try {
        readConfig();
        Class.forName(driverClass);
        con=DriverManager.getConnection(url, username, password);
        }catch(Exception e) {
            throw new RuntimeException("数据库连接失败");
        }
    }
    private static void readConfig() throws Exception{
        InputStream in=JDBCUtilsConfig.class.getClassLoader().getResourceAsStream("database.properties");
        Properties pro=new Properties();
        pro.load(in);
        driverClass=pro.getProperty("driverClass");
        url=pro.getProperty("url");
        username=pro.getProperty("username");
        password=pro.getProperty("password");
    }
    public static Connection getConnection() {
        return con;
    }
}

database.properties

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybase
username=root
password=123456

MailUtils.java

package cn.ctgu.mail;

import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMessage.RecipientType;

public class MailUtils {

    //email:邮件发给谁    subject:代表主题     emailMsg：代表内容
    public static void sendMail(String email, String subject,String emailMsg)
            throws AddressException, MessagingException {
        // 1.创建一个程序与邮件服务器会话对象 Session

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "SMTP");//发邮件协议
        props.setProperty("mail.host", "localhost");//发送邮件的服务器地址
        props.setProperty("mail.smtp.auth", "true");// 指定验证为true

        // 创建验证器
        Authenticator auth = new Authenticator() {
            public PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("tom", "123456");//发邮件的账号的验证
            }
        };

        Session session = Session.getInstance(props, auth);

        // 2.创建一个Message，它相当于是邮件内容
        Message message = new MimeMessage(session);

        message.setFrom(new InternetAddress("aaa@qq.com")); // 设置发送者

        message.setRecipient(RecipientType.TO, new InternetAddress(email)); // 设置发送方式与接收者

        message.setSubject(subject);//设置邮件的主题
        // message.setText("这是一封**邮件，请<a href='#'>点击</a>");

        message.setContent(emailMsg, "text/html;charset=utf-8");

        // 3.创建 Transport用于将邮件发送

        Transport.send(message);
    }
}

BirthdayListener.java

package cn.ctgu.birthday;

import java.sql.Connection;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

import javax.mail.MessagingException;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;


import cn.ctgu.dao.JDBCUtilsConfig;
import cn.ctgu.mail.MailUtils;

@WebListener
public class BirthdayListener implements ServletContextListener{

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
        //当web应用启动，开启任务调动————功能在用户的生日前发送邮件
        //开启一个定时器
        Timer timer=new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {

            @Override
            public void run() {
                // 为当前的生日的用户发邮件
                //1、获得今天过生日的人
                //获得今天的日期
                SimpleDateFormat format=new SimpleDateFormat("MM-dd");
                String currentDate=format.format(new Date());
                //根据当前时间从数据库查询今天过生日的人
                Connection con=JDBCUtilsConfig.getConnection();
                QueryRunner runner=new QueryRunner();
                String sql="select * from customer where birthday like?";
                List<Customers>customerList=null;
                try {
                    customerList=runner.query(con, sql, "%"+currentDate+"%", new BeanListHandler<Customers>(Customers.class));
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                //2、发邮件
                if(customerList!=null&&customerList.size()>0) {
                    for(Customers c:customerList) {
                        String emailMsg="亲爱的"+c.getRealname()+",生日快乐！";
                        try {
                            MailUtils.sendMail(c.getEmail(),"生日祝福", emailMsg);
                            System.out.println(c.getRealname()+"邮件发送完毕");
                        } catch (MessagingException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }

            }
        }, new Date(), 1000*5);
        //实际开发中起始时间是一个固定的时间
        //实际开发中间隔时间是1天
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        // TODO Auto-generated method stub

    }

}

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