Servlet笔记9--Cookie

Cookie：

　　使用Cookie机制实现十天内免登陆：

　　Servlet程序：

  1 package com.bjpowernode.javaweb.servlet;
  2 
  3 import java.io.IOException;
  4 import java.io.PrintWriter;
  5 import java.sql.Connection;
  6 import java.sql.DriverManager;
  7 import java.sql.PreparedStatement;
  8 import java.sql.ResultSet;
  9 import java.sql.SQLException;
 10 
 11 import javax.servlet.ServletException;
 12 import javax.servlet.http.Cookie;
 13 import javax.servlet.http.HttpServlet;
 14 import javax.servlet.http.HttpServletRequest;
 15 import javax.servlet.http.HttpServletResponse;
 16 
 17 /**
 18  * 检查登录时服务器是否接收到前端页面发送的Cookie，
 19  * 若收到则直接登录，登录成功则跳转到成功页面，登录失败则跳转到失败页面，
 20  * 若没收到则再跳转到登录页面
 21  * @author qjj
 22  *
 23  */
 24 public class CheckLoginStatusServlet extends HttpServlet {
 25 
 26     private static final long serialVersionUID = 1L;
 27 
 28     @Override
 29     protected void doGet(HttpServletRequest request, HttpServletResponse response)
 30             throws ServletException, IOException {
 31         //从request中获取所有的Cookie
 32         Cookie[] cookies = request.getCookies();
 33         String username = null;
 34         String password = null;
 35         if(cookies != null){
 36             //遍历Cookie
 37             for(Cookie cookie : cookies){
 38                 String cookieName = cookie.getName();
 39                 String cookieValue = cookie.getValue();
 40                 if("username".equals(cookieName)){
 41                     username = cookieValue;
 42                 }else if("password".equals(cookieName)){
 43                     password = cookieValue;
 44                 }
 45             }
 46         }
 47         
 48         if(username != null && password != null){
 49             //接收到Cookie
 50             //连接数据库验证用户名和密码
 51             Connection conn = null;
 52             PreparedStatement ps = null;
 53             ResultSet rs = null;
 54             boolean loginSuccess = false;
 55             String realName = null;
 56             try{
 57                 Class.forName("com.mysql.jdbc.Driver");
 58                 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test1", "root", "248xiaohai");
 59                 String sql = "select id,username,password,realname from t_user where username=? and password=?";
 60                 ps = conn.prepareStatement(sql);
 61                 ps.setString(1, username);
 62                 ps.setString(2, password);
 63                 rs = ps.executeQuery();
 64                 if(rs.next()){
 65                     loginSuccess = true; 
 66                     realName = rs.getString("realname");
 67                 }
 68             } catch (Exception e) {
 69                 e.printStackTrace();
 70             } finally {
 71                 if(rs != null){
 72                     try {
 73                         rs.close();
 74                     } catch (SQLException e) {
 75                         e.printStackTrace();
 76                     }
 77                 }
 78                 if(ps != null){
 79                     try {
 80                         ps.close();
 81                     } catch (SQLException e) {
 82                         e.printStackTrace();
 83                     }
 84                 }
 85                 if(conn != null){
 86                     try {
 87                         conn.close();
 88                     } catch (SQLException e) {
 89                         e.printStackTrace();
 90                     }
 91                 }
 92             }
 93             //登录成功跳转到成功页面，失败跳转到失败页面
 94             if(loginSuccess){
 95                 //这里的成功页面已响应的方式发送到前端，是因为有动态参数realname的存在，之后学了JSP就不用这么写了
 96                 response.setContentType("text/html;charset=UTF-8");
 97                 PrintWriter out = response.getWriter();
 98                 out.print("<html>");
 99                 out.print("<head>");
100                 out.print("<title>欢迎页面</title>");
101                 out.print("</head>");
102                 out.print("<body>");
103                 out.print("欢迎");
104                 out.print(realName);
105                 out.print("访问");
106                 out.print("</body>");
107                 out.print("</html>");
108             }else{
109                 response.sendRedirect(request.getContextPath() + "/login_error.html");
110             }
111         }else{
112             //没接收到Cookie,则跳转到登录页面
113             response.sendRedirect(request.getContextPath() + "/login.html");
114         }
115     }
116     
117     
118 }

  1 package com.bjpowernode.javaweb.servlet;
  2 
  3 import java.io.IOException;
  4 import java.io.PrintWriter;
  5 import java.sql.Connection;
  6 import java.sql.DriverManager;
  7 import java.sql.PreparedStatement;
  8 import java.sql.ResultSet;
  9 import java.sql.SQLException;
 10 
 11 import javax.servlet.ServletException;
 12 import javax.servlet.http.Cookie;
 13 import javax.servlet.http.HttpServlet;
 14 import javax.servlet.http.HttpServletRequest;
 15 import javax.servlet.http.HttpServletResponse;
 16 
 17 /**
 18  * 登录页面的响应，登录成功先判断是否选择十天内免登录，若选择则先向浏览器发送Cookie，
 19  * 然后跳转到成功页面
 20  * 若登录失败，则跳转到失败页面
 21  * @author qjj
 22  *
 23  */
 24 public class LoginServlet extends HttpServlet {
 25 
 26     private static final long serialVersionUID = 1L;
 27 
 28     @Override
 29     protected void doPost(HttpServletRequest request, HttpServletResponse response)
 30             throws ServletException, IOException {
 31         //设置字符编码方式
 32         request.setCharacterEncoding("UTF-8");
 33         //获取用户名和密码
 34         String username = request.getParameter("username");
 35         String password = request.getParameter("password");
 36         //连接数据库验证用户名和密码
 37         Connection conn = null;
 38         PreparedStatement ps = null;
 39         ResultSet rs = null;
 40         boolean loginSuccess = false;
 41         String realName = null;
 42         try{
 43             Class.forName("com.mysql.jdbc.Driver");
 44             conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test1", "root", "248xiaohai");
 45             String sql = "select id,username,password,realname from t_user where username=? and password=?";
 46             ps = conn.prepareStatement(sql);
 47             ps.setString(1, username);
 48             ps.setString(2, password);
 49             rs = ps.executeQuery();
 50             if(rs.next()){
 51                 loginSuccess = true; 
 52                 realName = rs.getString("realname");
 53             }
 54         } catch (Exception e) {
 55             e.printStackTrace();
 56         } finally {
 57             if(rs != null){
 58                 try {
 59                     rs.close();
 60                 } catch (SQLException e) {
 61                     e.printStackTrace();
 62                 }
 63             }
 64             if(ps != null){
 65                 try {
 66                     ps.close();
 67                 } catch (SQLException e) {
 68                     e.printStackTrace();
 69                 }
 70             }
 71             if(conn != null){
 72                 try {
 73                     conn.close();
 74                 } catch (SQLException e) {
 75                     e.printStackTrace();
 76                 }
 77             }
 78         }
 79         //登录成功跳转到成功页面，失败跳转到失败页面
 80         if(loginSuccess){
 81             //登陆成功之后，获取用户是否选择了十天内免登陆
 82             String tenDayAutoLoginFlag = request.getParameter("tenDayAutoLoginFlag");
 83             if("ok".equals(tenDayAutoLoginFlag)){
 84                 //创建Cookie对象
 85                 Cookie cookie1 = new Cookie("username",username);
 86                 Cookie cookie2 = new Cookie("password",password);
 87                 //设置有效时间
 88                 cookie1.setMaxAge(60 * 60 * 24 * 10);
 89                 cookie2.setMaxAge(60 * 60 * 24 * 10);
 90                 //设置关联路径
 91                 cookie1.setPath(request.getContextPath());
 92                 cookie2.setPath(request.getContextPath());
 93                 //发送Cookie给浏览器
 94                 response.addCookie(cookie1);
 95                 response.addCookie(cookie2);
 96             }
 97             
 98             response.setContentType("text/html;charset=UTF-8");
 99             PrintWriter out = response.getWriter();
100             out.print("<html>");
101             out.print("<head>");
102             out.print("<title>欢迎页面</title>");
103             out.print("</head>");
104             out.print("<body>");
105             out.print("欢迎");
106             out.print(realName);
107             out.print("访问");
108             out.print("</body>");
109             out.print("</html>");
110         }else{
111             response.sendRedirect(request.getContextPath() + "/login_error.html");
112         }
113     }
114 }

　　前端HTML：

 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
 2 <html>
 3   <head>
 4     <title>登录页面</title>
 5     
 6     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 7     <meta http-equiv="description" content="this is my page">
 8     <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 9     
10     <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
11 
12   </head>
13   
14   <body>
15     
16     <form action="/prj-servlet-20/login" method="post">
17         用户名
18             <input type="text" name="username">
19             <br>
20         密码
21             <input type="password" name="password">
22             <br>
23         <input type="checkbox" name="tenDayAutoLoginFlag" value="ok">十天内免登陆<br>
24         <input type="submit" value="登录">
25     </form>
26 
27   </body>
28 </html>

 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
 2 <html>
 3   <head>
 4     <title>登录失败</title>
 5     
 6     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 7     <meta http-equiv="description" content="this is my page">
 8     <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 9     
10     <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
11 
12   </head>
13   
14   <body>
15     
16     登录失败，用户名不存在或者密码错误，请<a href="/prj-servlet-20/login.html">重新登录</a>
17 
18   </body>
19 </html>

　　web.xml：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 3     xmlns="http://java.sun.com/xml/ns/javaee" 
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 5     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
 6     id="WebApp_ID" version="2.5">
 7     <!-- 设置isLogin为欢迎页面 -->
 8     <welcome-file-list>
 9         <welcome-file>isLogin</welcome-file>
10     </welcome-file-list>
11     
12     <servlet>
13         <servlet-name>login</servlet-name>
14         <servlet-class>com.bjpowernode.javaweb.servlet.LoginServlet</servlet-class>
15     </servlet>
16     <servlet-mapping>
17         <servlet-name>login</servlet-name>
18         <url-pattern>/login</url-pattern>
19     </servlet-mapping>
20     
21     <servlet>
22         <servlet-name>isLogin</servlet-name>
23         <servlet-class>com.bjpowernode.javaweb.servlet.CheckLoginStatusServlet</servlet-class>
24     </servlet>
25     <servlet-mapping>
26         <servlet-name>isLogin</servlet-name>
27         <url-pattern>/isLogin</url-pattern>
28     </servlet-mapping>
29 </web-app>