JDBC_基础

public class JDBC {

    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            // 1.注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            // 2.创建连接
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?user=root&password=123456");
            // 3.创建执行SQL语句的对象
            statement = connection.createStatement();
            // 4.执行SQL语句并返回结果集
            resultSet = statement.executeQuery("select * from user;");
            // 5.遍历输出
            while (resultSet.next()) {
                System.out.print(resultSet.getObject(1) + "   ");//按照列的索引获取
                System.out.print(resultSet.getObject(2) + "   ");
                System.out.print(resultSet.getObject(3) + "   ");
                System.out.print(resultSet.getObject(4) + "   ");
                System.out.println(resultSet.getObject(5) + "   ");
            }
        } catch (Exception e) {
            // TODO: handle exception
        } finally {
             //6.关闭连接
            if (resultSet != null) {
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (statement != null) {
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

这样做的不好处是，如果我要进增删改等操作，每次都需要写建立连接和释放连接的代码。所以，可以考虑用封装的思想把建立连接和释放连接写到工具类里面去。