Hibernate一对一条件抓取

Question

我正在使用hibernate在car和person表之间进行一对一映射。但一个人可能有车，也可能没有车。现在，在使用hibernate标准从person表中获取记录时，我只想获取那些拥有汽车的人，即person表中存在相应汽车表条目的条目。如何使用hibernate标准/别名实现这一点？

下面是一段代码。请提供获取结果所需的条件或别名：

@Getter
@Setter
@Entity
@Table(name = "Person")
public class Person implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Person_ID")
    private Long personId;

    @OneToOne(mappedBy = "personAsset", cascade = CascadeType.ALL)
    private Car car;
}

@Getter
@Setter
@Entity
@Table(name = "Car")
public class Car implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Car_ID")
    private Long carId;

    @OneToOne
    @JoinColumn(name = "Person_ID")
    private Person personAsset;
}

Answer 1

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Person> query = cb.createQuery(Person.class);
Root<Person> person = query.from(Person.class);
Predicate predicate = cb.isNotNull(person.join("car"));
predicates.add(predicate );

Answer 2

你要找的是@OneToOne注释上的cascadeType孤儿移除=true。

这是你的班级会是什么样子：

@Getter
@Setter
@Entity
@Table(name = "Car")
public class Car implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Car_ID")
    private Long carId;

    @OneToOne(fetch=FetchType.EAGER , cascade=CascadeType.ALL, orphanRemoval=true)
    @JoinColumn(name = "Person_ID")
    private Person personAsset;
}