Question

我尝试使用JPA 2.0 Criteria API构建查询，基于这两个实体：

person(id, name)
address(person_id, house_no, street, city, country)

相应的实体是：

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

    @Id
    private Integer id;

    private String name;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "id")
    private Address address;

}

@Entity
@Table(name = "address")
public class Address {

    @Id
    @Column(name = "person_id")
    private Integer personId;

    @Column(name = "house_no")
    private String houseNumber;

    private String street;

    private String city;

    private String country;
}

现在，我想要获取所有人，我有一个类似的查询：

 List<Person> getAll() {
    CriteriaBuilder cb = manager.getCriteriaBuilder();
    CriteriaQuery<Person> cq = cb.createQuery(Person.class);
    Root<Person> root = cq.from(Person.class);
    CriteriaQuery<Person> all = cq.select(root);
    TypedQuery<Person> tq = manager.createQuery(all);
    List<Person> res = tq.getResultList();
    return res;
}

虽然这个查询有效，并且给了我所有拥有地址成员的人。我只想要城市和乡村的田地，我不想去找house_no和街道。

SQl查询将是：

select p.*, a.city, a.country from person as p left join address as a on p.id=a.person_id;

上述查询的JPQL可能类似于：

SELECT p, p.address.city, p.address.country FROM person p LEFT JOIN p.address address

但这似乎不起作用!!人实体持有地址，不能保留城市和国家属性。我如何把正确的JPQL和相应的JPA 2.0标准查询？或者我是否必须更改我的实体结构？

从jpa left outer join

0 个答案: