Web应用开发

连接数据库并拉出数据

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
/**
 * 
 */
package cn.edu.nsu.infoSubSys.db.demo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;

/**
 * @author Pu_Junming
 *
 */

public class UsersDAO {
	// 全局数据定义（属性.成员变量定义）
	private Connection connection;
	private PreparedStatement pst;
	private ResultSet rst;
	// 处理数据（方法【构造方法 + 行为方法】）
	public UsersDAO() {
		
	}
	
	public UsersDAO(Connection connection,PreparedStatement pst,ResultSet rst) {
			this.connection = connection;
			this.pst = pst;
			this.rst = rst;
		}
	
	// 行为方法
	public void selectById(int id) throws ClassNotFoundException, SQLException {
		// 加载JDBC驱动
		Class.forName("com.mysql.cj.jdbc.Driver");
		// 获得数据库连接
		connection =  DriverManager.getConnection("jdbc:mysql://172.17.130.84:3306/infosubsysdb?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false", "root", "pujunming5893");
		// 封装SQL语句
		String sql = "SELECT * FROM users WHERE users_id=?";
		pst = connection.prepareStatement(sql);
		// 参数绑定
		pst.setObject(1, id);
		// 执行AQL
		rst =  pst.executeQuery();
		// 处理执行结果
		// next() 判断有没有下一条记录，如果有返回true，进入下一条记录，false则直接退出
		ResultSetMetaData resultSetMetaData= rst.getMetaData();
		while (rst.next()) {
			// 获取列标签
			for (int i = 0; i < resultSetMetaData.getColumnCount(); i++) {
				String columnLabel = resultSetMetaData.getColumnLabel(i+1);
				Object object = rst.getObject(columnLabel);
				System.out.print(object + "\t");
			}
			System.out.println();
		}
		// 关闭数据库连接
		if (rst != null) {
			rst.close();
		}
		if (connection != null) {
			connection.close();
		}
		if (pst != null) {
			pst.close();
		}
		// 
	}
	/**
	 * @param args
	 * @throws SQLException 
	 * @throws ClassNotFoundException 
	 */
	public static void main(String[] args){
		// TODO Auto-generated method stub
		UsersDAO usersDAO = new UsersDAO();
		try {
			usersDAO.selectById(1);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}