一、JDBC概念 二、JDBC常用四个核心对象    DriverManager        getConnection();    Connection        createStatement();        prepareStatement();    Statement(PreparedStatement)        ResultSet executeQuery();        int executeUpdate();        boolean execute();        delete from users where id = ?         ps.setInt(1, 5);    ResultSet         next();        getInt();        getString();        getDouble();        getDate();        ...        三、编写一个java应用步骤：    1、创建项目，添加jar包    2、编写操作数据库的类        try {            // 加载驱动            Class.forName("com.mysql.jdbc.Driver");            // 创建连接Connection            Connection conn = DriverManager.getConnection("jdbc:mysql:///day06","root","abc");            // 获取执行sql的statement对象            // conn.createStatement();            PreparedStatement ps = conn.prepareStatement("select * from users where id = ? and name = ?");            ps.setInt(1, 5);            ps.setString(2, "tom");            // 执行语句，并返回结果            ResultSet rs = ps.executeQuery();            // 处理结果            while (rs.next()) {                User u = new User();                u.setInt(rs.getInt("id"));                u.setName(rs.getString("name"));            }        } catch (Exception e) {            e.printStackTrace();        } finally {            //关闭资源            if (rs != null)                rs.close();            if (ps != null)                ps.close();            if (conn != null)                conn.close();        }