model-view-controller - 如何将表关系实现到实体对象中？

Question

我在数据库中有两个表：

Grade
+--------+--------------+-----------------+
| int id | varchar name | varchar teacher |
+--------+--------------+-----------------+
|      1 | CL-2A        | E. Wright       |
|      2 | CL-2B        | B. Springsteen  |
+--------+--------------+-----------------+

Student
+--------+------------------+-----------+
| int id | varchar name     | int grade |
+--------+------------------+-----------+
|      1 | Michael Wallings |         1 |
|      2 | Rowen Tress      |         1 |
|      3 | Alys Harverd     |         2 |
|      4 | Jeff Bass        |         1 |
|      5 | Harry Farewell   |         2 |
+--------+------------------+-----------+

正如您可能已经看到的那样，Student.grade指的是带有外键的Grade.id 。

现在我为这两个表制作了一些实体对象。但是我如何实现Student和Grade之间的关系？

public class Student {
    private int id;
    private String name;
    private int grade;   // Keep the grade as an int.
    ...

或者

public class Student {
    private int id;
    private String name;
    private Grade grade; // Hold a reference to the corresponding entity object Grade.
    ...

或者其他的东西？

第二个代码片段还要求我获取从数据库派生的成绩实体对象。