JDBC原始写法

在写代码之前,先创建数据库,建表,导入jdbc驱动包

package cn.itcast.jdbc;

import java.sql.*;

public class JDBCTest {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            //1.加载驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接
            String url ="jdbc:mysql://127.0.0.1:3306/mybatis-01";
            String username = "root";
            String paaaword = "821365";
            connection = DriverManager.getConnection(url, username, paaaword);
            //3.获取statement，preparedStatement
            String sql = "SELECT * FROM tb_user WHERE id = ?";
            preparedStatement = connection.prepareStatement(sql);
            //4.设置参数,这边的第一个参数代表了id=,第二个参数代表了id的值,如果查询条件有两个则第二个parameterIndex写2
            preparedStatement.setLong(1,2);
            //5.执行查询,获取结果集
            resultSet = preparedStatement.executeQuery();
            //6.处理结果集
            while (resultSet.next()){
                //参数可以写下标也可以写列名(表中的字段)
                System.out.println( resultSet.getString("name"));
                System.out.println(resultSet.getString("user_name"));
                System.out.println(resultSet.getInt("age"));


               //报错是因为表中没有这个字段,这是类中的属性   resultSet.getString("username");

            }
        }  finally {
            //7.关闭连接,释放资源
            resultSet.close();
            preparedStatement.close();
            connection.close();
        }

    }
}