JDBC预处理

public class PreparedStatement_ {
    public static void main(String[] args) throws Exception{

        Scanner scanner = new Scanner(System.in);

        //让用户输入管理员名和密码
        System.out.print("请输入管理员名字");
        String admin_name = scanner.nextLine();//如果希望看到注入效果
        System.out.print("请输入管理员密码");
        String admin_pwd = scanner.nextLine();

        Properties properties = new Properties();
        properties.load(new FileInputStream("src\\mysql.properties"));
        //获取相关的值(读取配置文件)
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String driver = properties.getProperty("driver");
        String url = properties.getProperty("url");

        //1.注册驱动
        Class.forName(driver);

        //2.得到链接
        Connection connection = DriverManager.getConnection(url, user, password);
        //3.得到PreparedStatement
        //3.1组织Sql语句 sql的? 想让与占位符
        String sql = "select name, pwd from admin where name =? and pwd = ?";
        //3.2preparedStatement 对象实现了 PreparedStatement 接口的实现类的对象
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        //3.3
        preparedStatement.setString(1,admin_name);
        preparedStatement.setString(2,admin_pwd);

        //4.执行select语句使用 excuteQuery
        //  如果执行的是 dml(update, insert, delete) 使用executeUpdate
        //  这里执行 excuteQuery 不要再写 sql
        ResultSet resultSet = preparedStatement.executeQuery();
        if (resultSet.next()){//如果查询到一条记录则说明该管理员存在
            System.out.println("恭喜, 登陆成功");
        }else {
            System.out.println("登陆失败");
        }

        //关闭连接
        resultSet.close();
        preparedStatement.close();
        connection.close();
    }
}