jsp之简单的用户登录系统（纯jsp）

来源：韩顺平之jsp视频教程

知识点：

1：如何在jsp页面间跳转

2：jsp如何去操作数据库

3：jsp中如何显示数据/如何分页

 1 <%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
 2 <%
 3 String path = request.getContextPath();
 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 5 %>
 6 
 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 8 <html>
 9   <head>
10     <base href="<%=basePath%>">
11     
12     <title>My JSP 'login.jsp' starting page</title>
13     
14     <meta http-equiv="pragma" content="no-cache">
15     <meta http-equiv="cache-control" content="no-cache">
16     <meta http-equiv="expires" content="0">    
17     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18     <meta http-equiv="description" content="This is my page">
19     <!--
20     <link rel="stylesheet" type="text/css" href="styles.css">
21     -->
22 
23   </head>
24   
25   <body bgcolor="green"><!-- 背景色为绿色 -->
26   <center>
27        用户登录<br>  
28   <hr/>
29   <form action="loginCl.jsp" method="post"> 
30    用户名：<input type="text" name="username"><br/>
31    <!-- &nbsp;空格 -->   
32    密&nbsp;&nbsp;码：<input type="password" name="passwd"><br/>
33   <input type="submit" value="登录">
34   <input type="reset" value="重置"> 
35   </form> 
36   </center>
37   </body>
38 </html>

 1 <%@ page language="java" import="java.util.*,java.sql.*"  pageEncoding="gb2312"%>
 2 <%
 3 String path = request.getContextPath();
 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 5 %>
 6 
 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 8 <html>
 9   <head>
10     <base href="<%=basePath%>">
11     
12     <title>My JSP 'loginCl.jsp' starting page</title>
13     
14     <meta http-equiv="pragma" content="no-cache">
15     <meta http-equiv="cache-control" content="no-cache">
16     <meta http-equiv="expires" content="0">    
17     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18     <meta http-equiv="description" content="This is my page">
19     <!--
20     <link rel="stylesheet" type="text/css" href="styles.css">
21     -->
22 
23   </head>
24   
25   <body>
26   <%
27   //接受用户名和密码，完成对用户的验证
28   String u=request.getParameter("username");
29   String p=request.getParameter("passwd");
30 
31   //到数据库中去验证用户
32   //1.加载驱动
33   Class.forName("com.mysql.jdbc.Driver");
34   //2.得到链接
35   Connection ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/spdb1","root","lszget"); //建立数据库链接
36   
37   //3.创建Statement
38   Statement stmt=ct.createStatement();
39   
40   //4.查询
41   ResultSet rs=stmt.executeQuery("select passwd from users where username='"+u+"'");
42   
43   //根据结果判断
44   if(rs.next()){
45   //说明用户存在
46       if(rs.getString(1).equals(p)){
47       
48       //一定合法
49        response.sendRedirect("wel.jsp?user="+u);
50       
51       }else{
52       //密码错误
53       response.sendRedirect("login.jsp?errNo=1");
54       }
55   }else{
56       //说明用户名错了
57       response.sendRedirect("login.jsp?errNo=2");
58       }
59   
60   
61   
62   
63  /* 
64   //验证
65   if(u.equals("shunping")&&p.equals("123")){
66   
67   //合法，跳转wel.jsp
68   //如何而将loginCl.jsp得到的数据传给下一个页面
69   //1.cookie 2.session 3.response.sendRedirect
70   response.sendRedirect("wel.jsp?user="+u);
71   }else{
72   //不合法，跳转到login.jsp
73   response.sendRedirect("login.jsp");
74   }
75   */
76   
77    %>
78     
79   </body>
80 </html>

loginCl.jsp

  1 <%@page import="javax.sound.midi.SysexMessage"%>
  2 <%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="gb2312"%>
  3 <%
  4 String path = request.getContextPath();
  5 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
  6 %>
  7 
  8 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
  9 <html>
 10   <head>
 11     <base href="<%=basePath%>">
 12     
 13     <title>My JSP 'wel.jsp' starting page</title>
 14     
 15     <meta http-equiv="pragma" content="no-cache">
 16     <meta http-equiv="cache-control" content="no-cache">
 17     <meta http-equiv="expires" content="0">    
 18     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 19     <meta http-equiv="description" content="This is my page">
 20     <!--
 21     <link rel="stylesheet" type="text/css" href="styles.css">
 22     -->
 23 
 24   </head>
 25   
 26   <body>
 27   
 28       登陆成功！！欢迎<%=request.getParameter("user")%><br/>
 29       <a href="login.jsp">返回重新登录</a>  
 30       <hr/>
 31       <h1> 用户信息列表</h1>
 32       
 33       <%
 34       //定义四个分页变量,作用域在整个页面
 35       int pageSize=3;//每页显示多少条记录
 36       int pageNow=1;//默认显示第一页
 37       int pageCount=0;//该值是通过pageSize和rowCount计算
 38       int rowCount=0;//该值从数据库中查询
 39       
 40       //接受用户希望显示的页数（pageNow）
 41       String s_pageNow=request.getParameter("pageNow");
 42       if(s_pageNow!=null){
 43       //接受到pageNow
 44       pageNow =Integer.parseInt(s_pageNow);
 45       System.out.println("pageNow =Integer.parseInt(s_pageNow);");
 46       }
 47       
 48       //查询得到rowCount
 49   //1.加载驱动
 50   Class.forName("com.mysql.jdbc.Driver");
 51   //2.得到链接
 52   Connection ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/spdb1","root","lszget"); 
 53   
 54   //3.创建Statement
 55   Statement stmt=ct.createStatement();
 56   
 57   //4.查询
 58   ResultSet rs=stmt.executeQuery("select count(*) from users ");
 59    //请注意一定要rs.next()   
 60       if(rs.next()){
 61       
 62       rowCount=rs.getInt(1);
 63      
 64       
 65       }
 66       //计算pageCount
 67       if(rowCount%pageSize==0){
 68       pageCount=rowCount/pageSize;
 69       }else{
 70       
 71        pageCount=rowCount/pageSize+1;
 72        
 73       }
 74       
 75       //查询出需要显示的记录
 76       /*实现类似top的功能，在SQL Server中和MySQL中使用到的SQL语句是不同的
 77       1、在SQL Server中，我们使用  select top N * from tablename来查询tablename表中前N条记录
 78       select * from users limit "+pageSize*(pageNow-1)+" ,"+pageSize+"
 79       2、在MySQL中，则使用select * from users limit M,N ,M表示从第M+1条记录开始，N表示返回N条记录
 80       rs=stmt.executeQuery("select  "+pageSize+" * from users where userId not in (select top "
 81       +pageSize*(pageNow-1)+" userId from users)");
 82                   数据库数据成倍增加
 83       INSERT INTO users(username,passwd,email,grade)SELECT username,passwd,email,grade FROM users
 84       */
 85       
 86       rs=stmt.executeQuery("select * from users limit "+pageSize*(pageNow-1)+" ,"+pageSize+" ");
 87       
 88       //显示
 89       %>
 90       
 91       
 92       <table border="1"> 
 93       <!-- TableRow 对象代表一个 HTML 表格行 -->
 94       <tr><td>用户id</td><td>用户名字</td><td>用户密码</td><td>电子邮件</td><td>用户级别</td></tr>
 95       
 96     
 97       
 98       <%
 99       while(rs.next()){
100       %>
101       
102         <tr><td><%=rs.getInt(1)%></td><td><%=rs.getString(2)%></td>
103         <td><%=rs.getString(3)%></td><td><%=rs.getString(4)%></td>
104         <td><%=rs.getInt(5) %></td></tr>
105       <%
106       
107       } 
108       
109       %>
110        </table>
111        
112        <%
113        //上一页
114        if(pageNow!=1){
115         out.println("<a href=wel.jsp?pageNow="+(pageNow-1)+">[上一页]</a>");
116         }
117        
118        //显示超链接  
119        for(int i=1;i<=pageCount;i++){
120         //韩顺平代码： out.println("<a href=#wel.jsp?pageNow="+i+" >["+i+"]</a>");
121         //加#有问题，？？？
122         out.println("<a href=wel.jsp?pageNow="+i+" >["+i+"]</a>");
123    
124        
125        }
126           //下一页
127         if(pageNow!=pageCount){
128         out.println("<a href=wel.jsp?pageNow="+(pageNow+1)+">[下一页]</a>");
129         }
130        
131         %>
132       
133     
134       
135   </body>
136 </html>

wel.jsp