java - Hibernate 对带有额外列的多对多关系的查询

Question

我是 Hibernate 的新手，由于需要额外的列，我正在尝试弄清楚如何查询映射为实体的多对多关系。

特别是，按照我在 codejava.net ( http://www.codejava.net/frameworks/hibernate/hibernate-many-to-many-association-with-extra-columns-in-join-table-example ) 找到的示例，我映射了如下关系:

学生.java

@Entity
public class Student implements Serializable {

    @Id
    @Column
    private String email;

    @Column(nullable = false)
    private String password;

    @Column(nullable = false)
    private String name;

    @Column(nullable = false)
    private String surname;

    // Constructor, getters, setters, hashcode, equals
 }

类(class).java

@Entity
@Table( 
    uniqueConstraints = @UniqueConstraint(
                            columnNames {"name","year"})
)
public class Course implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column
    private long id;

    @Column
    private String name;

    @Column
    private String year;

    @OneToMany(mappedBy = "course")
    private Set<Student_Course> students = new LinkedHashSet<>();

    // Constructor, getters, setters, hashcode, equals
}

Student_Course.java

@Entity
public class Student_Course implements Serializable {

    @Id
    @GeneratedValue (strategy = GenerationType.IDENTITY)
    @Column
    private long id; 

    @ManyToOne
    @JoinColumn(name = "student_email")
    private Student student;

    @ManyToOne
    @JoinColumn(name = "course_id")
    private Course course;

    @Column(nullable = false,
            columnDefinition = "int default 0")
    private int score;

    // Constructor, getters, setters, hashcode, equals
}

现在我想要实现的是通过 hql 查询找出就读给定类(class)的学生的姓名(我知道类(class)的名称和年份)。 我知道这可能很简单，但我无法在 HQL 中生成有效的查询。

提前谢谢您。

Answer 1

我相信这个查询可以做你想做的事:

SELECT sc.student.name, sc.student.surname
FROM Course c JOIN c.students sc 
WHERE c.name = :name AND c.year = :year