JavaWeb 监听器listener 学习与简单应用
Java窗体程序使用监听器
效果：点击按钮，控制台出现文字
代码如下
import javax.swing.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Date; public class edu_Listener { public static void main(String[] args) { //创建窗口 JFrame frame = new JFrame(); //设置窗口大小 frame.setSize(250,200); //设置窗口位置 frame.setLocation(350,250); //创建按钮 JButton btn = new JButton("Click"); //创建监听器 ActionListener listener = new ActionListener() { //处理事件的方法（事件处理器） @Override public void actionPerformed(ActionEvent e) { String dateStr = new Date(e.getWhen()).toString(); System.out.println(dateStr); System.out.println("Hello world !"); } };//注意这里的分号 // 将监听器注册到按钮（此后监听器会一直处于监听按钮的状态） btn.addActionListener(listener); //将按钮添加到窗口 frame.add(btn); //设置窗口显示状态 frame.setVisible(true); System.out.println("执行完毕！"); } }
Javaweb 使用监听器
？ | 课件只写了一半
监听器类
类名：MyServletContextListener
代码：
import jakarta.servlet.*; import jakarta.servlet.http.*; import jakarta.servlet.annotation.*; @WebListener public class MyServletContextListener implements ServletContextListener, HttpSessionListener, HttpSessionAttributeListener { public MyServletContextListener() { } // 在创建ServletContext对象时调用 @Override public void contextInitialized(ServletContextEvent sce) { /* This method is called when the servlet context is initialized(when the Web application is deployed). */ } // 在销毁ServletContext对象时地调用 @Override public void contextDestroyed(ServletContextEvent sce) { /* This method is called when the servlet Context is undeployed or Application Server shuts down. */ } @Override public void sessionCreated(HttpSessionEvent se) { /* Session is created. */ } @Override public void sessionDestroyed(HttpSessionEvent se) { /* Session is destroyed. */ } @Override public void attributeAdded(HttpSessionBindingEvent sbe) { /* This method is called when an attribute is added to a session. */ } @Override public void attributeRemoved(HttpSessionBindingEvent sbe) { /* This method is called when an attribute is removed from a session. */ } @Override public void attributeReplaced(HttpSessionBindingEvent sbe) { /* This method is called when an attribute is replaced in a session. */ } }
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> <!-- 配置ServletContextListener生命周期监听器--> <listener> <listener-class>MyServletContextListener</listener-class> </listener> </web-app>
