原生JDBC的代码

package com.fdy.javacTest;

import java.sql.*;

/**
 * @Description:
 * @author: fdy
 * @date: 2020/3/10 22:10
 */
public class JDBCDemo {
    public static void main(String[] args) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
        // 加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
        // 通过驱动管理类获取数据库链接
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8", "root", "root");
        // 定义sql语句 ?表示占位符
            String sql = "select * from user where username = ?";
        // 获取预处理statement
            preparedStatement = connection.prepareStatement(sql);
        // 设置参数，第一个参数为sql语句中参数的序号（从1开始），第二个参数为设置的参数值
            preparedStatement.setString(1, "小花");
        // 向数据库发出sql执行查询，查询出结果集
            resultSet = preparedStatement.executeQuery();
        // 遍历查询结果集
            while (resultSet.next()) {
                System.out.println(resultSet.getString("id") + " " + resultSet.getString("username"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
        // 释放资源
            if (resultSet != null) {
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (preparedStatement != null) {
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}