第15周作业

题目：

编写一个应用程序，输入用户名和密码，访问test数据库中t_login表（字段包括id、username、password），验证登录是否成功。在上一题基础上，当登录成功后，将t_user表（id、name、sex、birthday）的信息进行显示（要求使用DB.java完成登录和获取t_user表中数据的操作），最后再对t_user表进行一条记录的添加操作。

代码：

DB类：

 1 package 第15周作业;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.PreparedStatement;
 6 import java.sql.ResultSet;
 7 import java.sql.SQLException;
 8 
 9 import com.mysql.cj.xdevapi.Statement;
10 /**
11  * 封装连接数据库以及增删改查操作。
12  *
13  */
14 public class DB {
15     private static DB db;
16     private Connection con;
17     private PreparedStatement ps;
18     private ResultSet rs;
19     static {
20         try {
21             Class.forName("com.mysql.cj.jdbc.Driver");
22         } catch (ClassNotFoundException e) {
23             e.printStackTrace();
24         }
25     }
26 
27     public static DB getInstance() {
28         if (db == null) {
29             db = new DB();
30         }
31         return db;
32     }
33 
34     private DB() {// 通过构造方法创建数据库链接
35         try {
36             con = DriverManager.getConnection("jdbc:mysql://localhost:3306/java?serverTimezone=UTC", "root", "");
37         } catch (SQLException e) {
38             e.printStackTrace();
39         }
40     }
41 
42     public ResultSet DBQuery(String sql, Object[] field) {
43         try {
44             ps = con.prepareStatement(sql);
45             if (field.length > 0) {
46                 for (int i = 0; i < field.length; i++) {
47                     ps.setObject(i + 1, field[i]);
48                 }
49             }
50             rs = ps.executeQuery();
51         } catch (SQLException e) {
52             e.printStackTrace();
53         }
54         return rs;
55     }
56 
57     public ResultSet DBQuery(String sql) {
58         try {
59             ps = con.prepareStatement(sql);
60             rs = ps.executeQuery();
61         } catch (SQLException e) {
62             e.printStackTrace();
63         }
64         return rs;
65     }
66 
67     public int DBModify(String sql, Object[] field) {
68         int n = 0;
69         try {
70             ps = con.prepareStatement(sql);
71             if (field.length > 0)
72                 for (int i = 0; i < field.length; i++) {
73                     ps.setObject(i + 1, field[i]);
74                 }
75             n = ps.executeUpdate();
76         } catch (SQLException e) {
77             e.printStackTrace();
78         }
79         return n;
80     }
81 
82     public void close() {
83         try {
84             if (rs != null) {
85                 rs.close();
86             }
87             ps.close();
88             con.close();
89         } catch (SQLException e) {
90             e.printStackTrace();
91         }
92     }
93 }

测试类：

 1 package 第15周作业;
 2 
 3 import java.sql.ResultSet;
 4 import java.sql.SQLException;
 5 import java.util.Scanner;
 6 
 7 import javax.swing.plaf.synth.SynthStyle;
 8 import javax.xml.crypto.Data;
 9 
10 /**
11  * 
12  * 
13  * 调用数据库进行增删改查
14  *
15  */
16 public class Test {
17 
18     public static void main(String[] args) {
19         DB db = DB.getInstance();
20         boolean flag = false;
21         Scanner scan = new Scanner(System.in);
22         String[] user = new String[2];
23         user[0] = scan.next();
24         user[1] = scan.next();
25         String sql = "SELECT * FROM t_login where username = ? AND password=?";
26         ResultSet rs = db.DBQuery(sql, user);
27         try {
28             if (rs.next()) {
29                 System.out.println("登录成功！");
30                 flag = true;
31             }
32         } catch (SQLException e) {
33             e.printStackTrace();
34         }
35         if (flag) {
36             sql = "select id,name,CASE sex WHEN 0 THEN '男' ELSE '女' END as sex,birthday from t_user";
37             rs = db.DBQuery(sql);
38             try {
39                 while (rs.next()) {
40                     System.out.print(rs.getInt(1));
41                     System.out.print("  ");
42                     System.out.print(rs.getString(2));
43                     System.out.print("  ");
44                     System.out.print(rs.getString(3));
45                     System.out.print("  ");
46                     System.out.println(rs.getString(4));
47                 }
48             } catch (SQLException e) {
49                 e.printStackTrace();
50             }
51             String name = "a";
52             int sex = 0;
53             String date = "1998-01-01";
54             sql = "insert into t_user (name,sex,birthday)values(?,?,?)";
55             if (db.DBModify(sql, new Object[] { name, sex, date }) > 0) {
56                 System.out.println("更新成功");
57             } else {
58                 System.out.println("数据未更改");
59             }
60         } else {
61             System.out.println("账号或密码错误");
62         }
63 
64     }
65 
66 }