java - JPA - 字段的列数必须与引用的主键相同

Question

在我的项目中，我有两个类:School 和 Teacher。一所学校可以指派多名教师。这是我到目前为止的代码:

@Entity
@Table(name = "schools", uniqueConstraints = {
    @UniqueConstraint(columnNames = {
            "name"
    }})
public class School {

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

...

@OneToMany(fetch = FetchType.LAZY)
@JoinTable(name = "teachers",
        joinColumns = @JoinColumn(name = "school_id"),
        inverseJoinColumns = @JoinColumn(name = "teacher_id"))
private Set<Teacher> teachersList = new HashSet<>();

另一个类如下所示:

@Entity
@Table(name = "teachers", uniqueConstraints = {
    @UniqueConstraint(columnNames = {
            "id"
    })
})
public class Teacher {

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

...

现在，当我尝试构建这个项目时，我收到错误:

org.hibernate.MappingException: Foreign key (FK4hetjkgnpo354f7uwax5aewc0:teachers
 [teacher_id])) must have same number of columns as the
referenced primary key (teachers [school_id,teacher_id])

我在这里迷路了。我究竟缺少什么？谢谢!

Answer 1

@JoinTable 用于ManyToMany 关系，您必须在Many 实体端(教师)使用@JoinColumn

试试这个:

public class Teacher{
//...

@ManyToOne
@JoinColumn(name="fk_school_id") // this is your foreign key in your Teacher table of your DB
private School school;

}

但是，如果您还想检索每所学校的教师列表，则必须将其放入您的一个实体(学校)中:

@OneToMany(mappedBy="school")
private List<Teacher> teachers = new ArrayList();