Question

我有一个ManyToMany，我已经像这样映射了question。

请注意，为简单起见，我删除了样板

@Entity
class Person {

    @OneToMany(mappedBy = "person")
    @OrderBy("sort")
    private List<PersonAddress> adresses = new ArrayList<>();

}

@Entity
class PersonAdress {
    @EmbeddedId
    private PersonAdressId id;
    @Column
    private int sort;

    @ManyToOne
    private Person person;

    @ManyToOne
    private Address address;
}

@Entity
class Address {
    @OneToMany(mappedBy = "address")
    @OrderBy("sort")
    private List<PersonAddress> persons = new ArrayList<>();
}

@Embeddable
public class PersonAdressId implements Serializable {
    @Column(name = "person_id")
    private long personId;
    @Column(name = "address_id")
    private long addressId;
}

我正在尝试获取person的所有地址，并按sort属性排序。但由于某些原因，我得到了例外，或者我没有对它进行排序。

我尝试了以下内容：

"select p from Person p where p.id=pid join fetch p.address a order by a.sort"

我也尝试过：

Person person = entityManager.find(Person.class, personId);
person.getAddress() //<-- This should use the @OrderBy, but I don't get it ordered nor does it print out order by in the output

有人能说出为什么它无法正常工作吗？

Answer 1

您是否尝试过以下查询：

Select p From Person p Left Join p.adresses a Where p.id = :pid Order By a.sort

有关详细信息，请参阅HQL reference。

Answer 2

首先，您的映射是错误的：您想要Person和Address之间的多对多关联？那就是为什么你把PersonAddress实体放在中间？

在类Person中，它应该是：

@OneToMany(mappedBy = "person") private List<PersonAddress> personAdresses = new ArrayList<>();
在课程地址中，应该是：

@OneToMany(mappedBy = "address") private List<PersonAddress> personAddresses = new ArrayList<>();

只有这样，您的排序才会起作用，因为它是PersonAddress实体的成员

JPA 2：在ManyToMany中使用额外字段

2 个答案: