java - Hibernate: OneToOne: 同一类型的两个字段

Question

假设我有一个 Person 实体和一个 Animal 实体；一个人可以有两个最喜欢的动物，一个动物只能有一个 人喜欢他们的人(一个人喜欢一种动物使得其他人不再可能喜欢/看到该动物)。它是一个@OneToOne 映射:对于Person 中的两个Animal 字段和Person 中的两个字段动物。但是，在 Animal 中，firstPerson 应该 == 到 secondPerson。有没有一种方法可以只对 Animal 类中的一个 Person 字段执行以下操作？

Person.java:

@Entity
@SequenceGenerator(name="PERSON_SEQ", sequenceName="person_sequence")
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="PERSON_SEQ")
    private Long id;

    @Column
    private String name;

    public Person()  {}

    @OneToOne
    @JoinColumn(name = "firstAnimal")
    private Animal firstAnimal;
    @OneToOne
    @JoinColumn(name = "secondAnimal")
    private Animal secondAnimal;

    //getters and setters

Animal.java:

@Entity
@SequenceGenerator(name="PRIVATE_SEQ", sequenceName="private_sequence")
public class Animal {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="PRIVATE_SEQ")
    private Long id;

    @Column
    private String name;

   @OneToOne(mappedBy = "firstAnimal")
   private Person firstPerson;

   @OneToOne(mappedBy = "secondAnimal")
   private Person secondPerson;
...

Answer 1

在这种情况下，您可能希望使用 @OneToMany/@ManyToOne 来获得永久解决方案。

Person.java:

@Entity
@Table(name = "...")
public class Person {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "org.hibernate.id.UUIDGenerator")
    @Column(name="person_id")
    private Long id;

    @Column(name="...")
    private String name;

    @OneToMany(mappedBy = "owner", cascade = CascadeType.?)
    private List<Animal> animals;
    
}

Animal.java:

@Entity
@Table(name = "...")
public class Animal {
    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "org.hibernate.id.UUIDGenerator")
    @Column(name = "...")
    private Long id;

    @Column(name = "...")
    private String name;

    @ManyToOne
    @JoinColumn(name="columnName", referencedColumnName="person_id")
    private Person owner;

}

对于进一步的限制，例如一个人最多只能拥有 2 只最喜欢的动物，或者一只动物只能由 1 个人拥有，您可以使用代码逻辑检查它们。