1     /** 2      * 快速入门 3      */ 4     @Test 5     public void demo1() { 6         /** 7          *  * 1.加载驱动. 8          *    * 2.获得连接. 9          *  * 3.编写sql执行sql.10          *  * 4.释放资源.11          */12         // 1.加载驱动:13         // DriverManager.registerDriver(new Driver());14         // 查看源代码了 只要Driver类一加载,注册驱动.15         Connection conn = null;16         Statement stmt = null;17         ResultSet rs = null;18         try {19             Class.forName("com.mysql.jdbc.Driver");20             // 2.获得连接:21             conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day17", "root", "123");22             // 3.执行sql.23             // 3.1编写一个sql语句24             String sql = "select * from user";25             // 3.2创建一个执行sql的对象.26             stmt = conn.createStatement();27             // 3.3调用stmt中的方法执行sql语句28             rs = stmt.executeQuery(sql);29             // 3.4遍历结果集30             while(rs.next()){31                 int id = rs.getInt("id");32                 String username  = rs.getString("username");33                 String password  = rs.getString("password");34                 System.out.println(id+"    "+username+"     "+password);35             }36         } catch (Exception e) {37             e.printStackTrace();38         }finally{39             // 4.释放资源.40             if (rs != null) {41                 try {42                     rs.close();43                 } catch (SQLException sqlEx) { 44                     // ignore }45                 }46 47                 rs = null;48             }49 50             if (stmt != null) {51                 try {52                     stmt.close();53                 } catch (SQLException sqlEx) { 54                     // ignore }55                 }56 57                 stmt = null;58             }59                 60             if (conn != null) {61                 try {62                     conn.close();63                 } catch (SQLException sqlEx) { // ignore }64                 65                 }66                 // 手动设置为null. 67                 conn = null;68             }    69         }70     }