jpa - JPA 类 有田野孩子的人

Question

我有一个具有以下字段的数据库实体 Person：

1. ID
2. 父亲
3. 母亲

而且我需要创建带有字段子项的 JPA 实体类。像这样的东西：

@Entity
public class Person implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    @Column(name = "father")
    private Integer fatherID;

    @Column(name = "mother")
    private Integer motherID;

    @OneToMany(mappedBy = "fatherId")
    private List<Person> children;
    }

但问题是我还需要在mappedBy属性中确定母亲。结果可能如下所示：

SELECT * FROM person WHERE father = id OR mother = id

有人可以帮我解决这个问题吗？使用 JPA 可以完成这项任务吗？

Answer 1

您不能将“mappedBy”设置为非对象类型（因为这不是双向关系）。您必须具有 Person 类型（不是 Integer）的“mother”和“father”字段才能具有双向关系。得到父亲和母亲是微不足道的

Answer 2

Apart from mapping issues that have been pointed out...

Not a JPA expert but I don't think JPA has this case considered directly. I would solve this using two mappings and an auxiliar fake getter. Sample below:

@OneToMany(mappedBy = "father")
private List<Person> childrenIfFather();

@OneToMany(mappedBy = "mother")
private List<Person> childrenIfMother();

public getChildren() {
    if (childrenIfFather != null) return childrenIfFather();
    else return childrenIfMother();
}

Answer 3

尝试使用 EJBQL（或者此时是 JPQL？）来解决它：

  SELECT p FROM Person p WHERE p.father = ?1 OR p.mother = ?2

另外，我会考虑使用不是整数的东西作为id。从长远来看，它真的会咬你一口（可能是 long 或 BigInteger）。