在休眠中的另一个实体中两次使用相同的实体

Question

Let us say a class/entity named student which contains an id, father's occupation and mother's occupation and the entity classes are like this

Student class

@Entity
@Table(name = "student")
public class Student {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(nullable = false, unique = true, updatable = false)
    private int id;

    @OneToOne
    @JoinColumn(name = "occupationId")
    Occupation fathersOccupation;

    @OneToOne
    @JoinColumn(name = "occupationId")
    Occupation mothersOccupation;

}

and the Occupation class

@Entity
@Table(name = "occupation")
public class Occupation {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "occupationId")
    int occupationId;

    @Column
    String title;

}

When I tried @OneToOne mapping for both father's occupation and mother's occupation it is throwing exception, Repeated column in mapping for entity . I tried adding @Column(name="<columnName>") , but it is not allowed. I really want those two fields, fathersOccupation and mothersOccupation with oneToOne mapping in the student table.

Answer 1

@JoinColumn specify the name of the FK Column in your entity.

Your student entity have 2 FKs toward occupation, one for fathersOccupation and another one for mothersOccupation and you define mapping twice for the same. Ideally you should have fathers_occupation_id and mothers_occupation_id field in your student table and same attributes in your entity.

So you should put for each one the corresponding column name in your student table.

@JoinColumn(name ="fathers_occupation_id")
Occupation fathersOccupation;

@JoinColumn(name="mothers_occupation_id")
Occupation mothersOccupation;

Answer 2

If someone interesting in, the solution that worked for me was to rename mapping field in entity with @ManyToOne annotation and add prefix before "account_id":

@ManyToOne
@JoinColumn(name = "from_account_id") // add from_
private Account fromAcc;
@ManyToOne
@JoinColumn(name = "to_account_id") // add to_
private Account toAcc;