1.监听器：在GUI中经常使用
package com.hxl.listener; import java.awt.*; import java.awt.event.WindowEvent; import java.awt.event.WindowListener; public class TestPanel { public static void main(String[] args) { Frame frame = new Frame("2021中秋节快乐");//新建一个窗体 Panel panel = new Panel(null);//面板 frame.setLayout(null); frame.setBounds(300,300,500,500); frame.setBackground(new Color(0,0,255)); panel.setBounds(50, 50 ,300, 300); panel.setBackground(new Color(0,255,0)); frame.add(panel); frame.setVisible(true); //监听关闭事件 frame.addWindowListener(new WindowListener() { public void windowOpened(WindowEvent e) { System.out.println("打开"); } public void windowClosing(WindowEvent e) { System.out.println("关闭ing"); System.exit(0); } public void windowClosed(WindowEvent e) { System.out.println("关闭ed"); } public void windowIconified(WindowEvent e) { } public void windowDeiconified(WindowEvent e) { } public void windowActivated(WindowEvent e) { System.out.println("激活"); } public void windowDeactivated(WindowEvent e) { System.out.println("未激活"); } }); } }
2.用户登录后才能进入主页，用户注销后就不能进入首页
- 用户登录之后，向Session中放入用户的数据
- 进入主页的时候要判断用户是否登录，要求在过滤器中实现
- 首先我们先进入登录页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>登录</title> </head> <body> <form action="/servlet/login" method="post"> <input type="text" name="username"> <input type="submit"> </form> </body> </html>
- 进入登录页面后我们走一个请求
package com.hxl.servlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //获取前端请求的参数 String username = req.getParameter("username"); if(username.equals("admin")){ //登录成功,存了一个session req.getSession().setAttribute("Constant.USER_SESSION", req.getSession().getId()); resp.sendRedirect("/sys/success.jsp"); }else{ //登录失败 resp.sendRedirect("/sys/error.jsp"); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }
- 成功走成功的页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>主页</title> </head> <body> <%-- //没有下面的代码，就算没有admin也可以进入成功页面。这是jsp做的一种方法。我们一般不用 <% Object user_session = request.getSession().getAttribute("USER_SESSION"); if(user_session==null){ response.sendRedirect("/Login.jsp"); } %> --%> <h3>成功了</h3> <p><a href="/servlet/logout">注销</a> </p> </body> </html>
- 失败走失败的页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>错误</title> </head> <body> <h3>用户名写错了</h3> <p><a href="/Login.jsp">返回到登录页面</a> </p> </body> </html>
- 我们再加个权限验证过滤器
package com.hxl.servlet; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //获取前端请求的参数 String username = req.getParameter("username"); if(username.equals("admin")){ //登录成功,存了一个session req.getSession().setAttribute("Constant.USER_SESSION", req.getSession().getId()); resp.sendRedirect("/sys/success.jsp"); }else{ //登录失败 resp.sendRedirect("/sys/error.jsp"); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }
- 我们发现session的一个名字比较常用，所以我们将他变成常量
package com.hxl.util; public class Constant { public final static String USER_SESSION = "USER_SESSION"; }
- 每一个servlet、Filter都需要在xml中进行配置
<servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.hxl.servlet.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/servlet/login</url-pattern> </servlet-mapping> <servlet> <servlet-name>LoginOutServlet</servlet-name> <servlet-class>com.hxl.servlet.LoginOutServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginOutServlet</servlet-name> <url-pattern>/servlet/logout</url-pattern> </servlet-mapping> <filter> <filter-name>SysFilter</filter-name> <filter-class>com.hxl.filter.SysFilter</filter-class> </filter> <filter-mapping> <filter-name>SysFilter</filter-name> <url-pattern>/sys/*</url-pattern> </filter-mapping>
