Java操作MySQL数据库——查询表中数据

Java操作MySQL数据库——连接数据库

1. 在数据库中建立表

CREATE TABLE `user`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `password` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 303 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

SET FOREIGN_KEY_CHECKS = 1;

2.编写代码

import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class Main {
    //数据库连接
    private static Connection connection;
    //连接数据库的URL
    private static String url = "jdbc:mysql:///blog?useSSL=false";
    //连接数据库的账号
    private static String username = "root";
    //连接数据库的密码
    private static String password = "123456";

    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //加载数据库驱动
        Class.forName("com.mysql.jdbc.Driver");
        //获取数据库连接
        connection = DriverManager.getConnection(url, username, password);
        String sql = "select * from user";
        Statement stmt = connection.createStatement();
        ResultSet resultSet = stmt.executeQuery(sql);
        List<User> list = new ArrayList<User>();
        while (resultSet.next()) {
            int id = resultSet.getInt("id");
            String username = resultSet.getString("username");
            String password = resultSet.getString("password");
            list.add(new User(id, username, password));
        }
        for (User user : list) {
            System.out.println(user);
        }
        connection.close();
    }
}
class User {
    private Integer id;
    private String username;
    private String password;

    public User(Integer id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}