java - Hibernate - 学生评分系统。需要注释方面的帮助

Question

我正在使用 hibernate 开发一个学生信息系统，学生可以在其中拥有多个类(class)(和分数)。我希望我的 POJO 是这样的:

学生:student attributes + Set<Course>

类(class):course attributes + int marks

但是在数据库中，我有以下 3 个表。

create table STUDENT (
 STUDENT_ID BIGINT not null auto_increment primary key,
 // ... student type attributes
)

create table COURSE (
 COURSE_ID BIGINT not null auto_increment primary key,
 // ... course type attributes
)

create table STUDENT_COURSE_MARKS (
 STUDENT_ID BIGINT not null,
 COURSE_ID BIGINT not null,
 MARKS int default 0,
 CHECK (MARKS <= 100)
)

问题:

1. 我需要为每个数据库表创建一个 pojo>
2. 如何设置注释来实现此功能？

Answer 1

这是简单的映射:

@Entity
@Table(name = "STUDENT")
public Class Student {

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "student")
    private Set<StudentCourseMark> studentCourseMark = new HashSet<StudentCourseMark>(0);

}

@Entity
@Table(name = "COURSE")
public Class Course {

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "course")
    private Set<StudentCourseMark> studentCourseMark = new HashSet<StudentCourseMark>(0);

}

@Entity
@Table(name = "STUDENT_COURSE_MARKS")
public Class StudentCourseMark {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "STUDENT_ID")
    private Student student;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "COURSE_ID")
    private Course course;

    private List<Mark> marks = new ArrayList<Mark>(0);
}

当然，您可以在 StudentCourseMark 中的 STUDENT_ID、COURSE_ID 上使用 PrimaryKey，示例如下: http://www.mkyong.com/hibernate/hibernate-many-to-many-example-join-table-extra-column-annotation/

如何获得学生分数:

Student student = getStudentFromDB();
List<Mark> marks = student.getMarks();