Question

我有一个使用Hibernate 3.6来执行持久性的Java-SE 1.6 / JPA应用程序。这样的应用程序具有如下所示的域模型（以简化形式）：

@Entity
@Table(name = "students")
public class Student implements Serializable {

    // many fields, getters and setters

    @OneToMany(mappedBy="student", cascade=CascadeType.ALL)
    private List<Enrollment> enrollments = new ArrayList<Enrollment>();
    public Collection<Enrollment> getEnrollments() {
        return Collections.unmodifiableCollection(enrollments);
    }
}

@Entity
@Table(name = "enrollments")
public class Enrollment implements Serializable {

    // many fields, getters and setters

    @ManyToOne
    private Student student;
    public Student getStudent() {
        return student;
    }

    @OneToOne
    private Course course;
    public Course getCourse() {
        return course;
    }
}

@Entity
@Table(name = "courses")
public class Course implements Serializable {

    // many fields, getters and setters

}

因此，用简单的英语，这个模型使我们能够建模以下域规则：

“某位学生可同时参加多门课程。”

到目前为止，一切都在顺利运作。这里的问题是：

“如何选择在指定课程中注册的所有学生？”

所以，我有Course的实例，我的工作是选择与Student（间接）相关的Course的所有实例（通过{{1}的实例通过使用Hibernate查询。

有人可以给我一些意见和/或想法吗？

提前致谢。

Answer 1

试试这个

select s from Student s join s.enrollments e join e.course c where c.id = :courseId

使用标准

List<Student> students = session.createCriteria(Student.class).createAlias("enrollments", "e").createAlias("e.course", "c").add(Restrictions.eq("c.id", courseId)).list();

Hibernate Complex通过许多实体查询

1 个答案: