/**

      * 快速入门

      */

     @Test

     public void demo1() {

         /**

          *  * 1.加载驱动.

          *    * 2.获得连接.

          *  * 3.编写sql执行sql.

          *  * 4.释放资源.

          */

         // 1.加载驱动:

         // DriverManager.registerDriver(new Driver());

         // 查看源代码了 只要Driver类一加载,注册驱动.

         Connection conn = null;

         Statement stmt = null;

         ResultSet rs = null;

         try {

             Class.forName("com.mysql.jdbc.Driver");

             // 2.获得连接:

             conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day17", "root", "123");

             // 3.执行sql.

             // 3.1编写一个sql语句

             String sql = "select * from user";

             // 3.2创建一个执行sql的对象.

             stmt = conn.createStatement();

             // 3.3调用stmt中的方法执行sql语句

             rs = stmt.executeQuery(sql);

             // 3.4遍历结果集

             while(rs.next()){

                 int id = rs.getInt("id");

                 String username  = rs.getString("username");

                 String password  = rs.getString("password");

                 System.out.println(id+"    "+username+"     "+password);

             }

         } catch (Exception e) {

             e.printStackTrace();

         }finally{

             // 4.释放资源.

             if (rs != null) {

                 try {

                     rs.close();

                 } catch (SQLException sqlEx) {

                     // ignore }

                 }

                 rs = null;

             }

             if (stmt != null) {

                 try {

                     stmt.close();

                 } catch (SQLException sqlEx) {

                     // ignore }

                 }

                 stmt = null;

             }

             if (conn != null) {

                 try {

                     conn.close();

                 } catch (SQLException sqlEx) { // ignore }

                 }

                 // 手动设置为null.

                 conn = null;

             }

         }

     }