基于DAO模式和MVC模式完成一个用户管理程序,包括用户注册、用户登录、浏览用户列表和删除用户等四个功能。
要求：1）JSP页面中不允许出现Java代码，使用标签实现显示逻辑
          2）HTTP请求发送给Servlet，由Servlet负责调用DAO类，并转发给JSP页面
          3）浏览用户列表页面要支持分页功能

DBCon.java类：与数据库admin表连接，有插入，删除等动作；

 1 package db_admin;
 2 
 3 import java.sql.*;
 4 import java.sql.Connection;
 5 import java.sql.DriverManager;
 6 import java.sql.ResultSet;
 7 import java.sql.SQLException;
 8 
 9 public class DBCon {
10     private String dbDriver = "com.mysql.jdbc.Driver";
11     private String dbUrl = "jdbc:mysql://localhost:3306/book?useUnicode=true&characterEncoding=utf-8";
12     private String dbUser = "root";
13     private String dbPwd = "123456";
14     private Connection conn = null;
15 
16     public Connection getConnection() {
17         try {
18             Class.forName(dbDriver);
19             conn = DriverManager.getConnection(dbUrl, dbUser, dbPwd);
20         } catch (ClassNotFoundException e) {
21             e.printStackTrace();
22         } catch (SQLException e) {
23             e.printStackTrace();
24         }
25         return conn;
26     }
27 
28     public ResultSet doQurey(String sql) {
29         ResultSet rs = null;
30         conn = this.getConnection();
31         try {
32             Statement stmt = conn.createStatement();
33             rs = stmt.executeQuery(sql);
34         } catch (Exception e) {
35             e.printStackTrace();
36         }
37         return rs;
38     }
39 
40     public int doUpdate(String sql) {
41         int res = 0;
42         conn = this.getConnection();
43         try {
44             Statement stmt = conn.createStatement();
45             res = stmt.executeUpdate(sql);
46         } catch (Exception e) {
47             e.printStackTrace();
48         }
49         return res;
50     }
51 
52     public String checkUser(String username, String password) {
53         boolean has_username = false;
54         boolean password_correct = false;
55         ResultSet rs = null;
56         try {
57             rs = doQurey("select * from admin");
58         } catch (Exception e) {
59             e.printStackTrace();
60         }
61 
62         try {
63             while (rs.next()) {
64                 String temp_username = rs.getString("username");
65                 String temp_password = rs.getString("password");
66                 if (username.equals(temp_username)) {
67                     has_username = true;
68                     if (password.equals(temp_password)) {
69                         password_correct = true;
70 
71                         return "hasUserNameAndPasswordCorrect";
72 
73                     }
74 
75                     return "hasUserNameButPasswordInCorrect";
76 
77                 }
78 
79             }
80 
81         } catch (SQLException e) {
82 
83             e.printStackTrace();
84 
85         }
86 
87         return "hasNoUserName";
88 
89     }
90 
91     public void close() throws SQLException {
92         try {
93             conn.close();
94         } catch (Exception e) {
95             e.printStackTrace();
96         }
97     }
98 }

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