使用传统的jdbc方式操作数据库

现在开发中有了mybatis、jdbcTemplate之后，已经很少公司会直接使用jdbc来连接数据库了，但是无论是mybatis还是jdbcTemplate，其底层都是jdbc。

这篇文章就主要介绍一下怎么通过jdbc来连接数据库。

在这之前，创建数据库jdbc，在数据库下创建user表

/*
 Navicat Premium Data Transfer

 Source Server         : MaraDB
 Source Server Type    : MariaDB
 Source Server Version : 100605 (10.6.5-MariaDB)
 Source Host           : 127.0.0.1:3306
 Source Schema         : jdbc

 Target Server Type    : MariaDB
 Target Server Version : 100605 (10.6.5-MariaDB)
 File Encoding         : 65001

 Date: 13/07/2023 18:36:09
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` int(11) UNSIGNED NOT NULL AUTO_INCREMENT,
  `username` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL COMMENT '用户名',
  `password` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT '12345' COMMENT '密码',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '用户表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1, 'mumu', '12345');
INSERT INTO `user` VALUES (2, 'system', '12345');

SET FOREIGN_KEY_CHECKS = 1;

jdbc连接数据库的步骤：

第一步：加载驱动

mysql8.0之前

Class.forName("com.mysql.jdbc.Driver");

mysql8.0之后

Class.forName("com.mysql.cj.jdbc.Driver");

第二步：获取数据库连接（通过DriverManager）

String url = "jdbc:mysql://localhost:3306/jdbc";
String username = "root";
String password = username;

Connection connection = DriverManager.getConnection(url, username, password);

第三步：获取PreparedStatement对象

String sql = "select username, password from user";

PreparedStatement statement = connection.prepareStatement(sql);

第四步：执行SQL，如果是查询类的语句，得到查询结果

ResultSet resultSet = statement.executeQuery();

while (resultSet.next()) {
    String username = resultSet.getString("username");
    String password = resultSet.getString("password");

    System.out.println("username = " + username);
    System.out.println("password = " + password);
}

第五步：关闭数据库连接对象（建议写在finally语句块中）

完整的代码：

package com.example.jdbc;

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

import java.sql.*;

@SpringBootTest
class JdbcTests {
    String url = "jdbc:mysql://localhost:3306/jdbc";
    String username = "root";
    String password = username;

    @Test
    void testQuery() {
        Connection connection = null;
        String sql = "select username, password from user";

        try {
            connection = DriverManager.getConnection(url, username, password);

            PreparedStatement statement = connection.prepareStatement(sql);
            ResultSet resultSet = statement.executeQuery();

            while (resultSet.next()) {
                String username = resultSet.getString("username");
                String password = resultSet.getString("password");

                System.out.println("username = " + username);
                System.out.println("password = " + password);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    @Test
    void testUpdate() {
        Connection connection = null;
        String sql = "update user set password = ? where username = ?";

        try {
            connection = DriverManager.getConnection(url, username, password);

            PreparedStatement statement = connection.prepareStatement(sql);

            // 设置参数
            statement.setString(1, "mhxy1218");
            statement.setString(2, "mumu");

            int updates = statement.executeUpdate();

            System.out.println("本次修改共影响" + updates + "行记录。");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    @Test
    void testInsert() {
        Connection connection = null;
        String sql = "insert into user(username, password) values (?, ?)";

        try {
            connection = DriverManager.getConnection(url, username, password);

            PreparedStatement statement = connection.prepareStatement(sql);

            // 设置参数
            statement.setString(1, "heyunlin");
            statement.setString(2, "12345");

            int updates = statement.executeUpdate();

            System.out.println("本次共插入" + updates + "条记录。");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Test
    void testDelete() {
        Connection connection = null;
        String sql = "delete from user where username= ?";

        try {
            connection = DriverManager.getConnection(url, username, password);

            PreparedStatement statement = connection.prepareStatement(sql);

            // 设置参数
            statement.setString(1, "heyunlin");

            int updates = statement.executeUpdate();

            System.out.println("本次共删除" + updates + "条记录。");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

    }

}

PreparedStatement对象常用的方法有三个

• boolean execute()：一般不用，返回的是sql语句执行的结果，如果执行成功返回true，否则返回false；
• int executeUpdate()：用于执行DML语句，即insert/update/delete语句，返回受影响的行数；
• ResultSet executeQuery()：用于执行查询类的sql，通过ResultSet对象获取查询结果，mybatis中帮我们自动从ResultSet获取查询的所有字段值，并封装成了我们定义的entity对象；

文章的代码已开源，可按需获取

jdbc连接mysqlhttps://gitee.com/he-yunlin/jdbc.git好了，文章就分享到这里了，如果这篇文章对你有所帮助，不要忘了点赞+收藏哦~