JPA:查询实体内的可嵌入列表 [英] JPA: Query an embeddable List inside an entity

问题描述

我试图根据实体列表中的某些条件提取"可嵌入类.借助JPQL或Criteria API.我不是专业人士，所以请帮帮我.谷歌搜索了4个小时，没有任何结果.

I am trying to "extract" Embeddable classes based on some criterias from a list in an Entity. Either with the help of JPQL or Criteria API. I am not a pro at this, so please help me out. Been googling for 4 hours solid for an answer without any results.

这些是类:

@Entity
public class PostOffice {

    @Id
    private Long id;

    @ElementCollection(fetch=FetchType.LAZY)
    @CollectionTable(joinColumns=@JoinColumn(name = "CARRIERID"))
    private List<PostalCarrier> carriers;

}


@Embeddable
public class PostalCarrier {

    @JoinColumn(name = "area")
    private Area area;

} 


@Entity
public class Area {

    @Id
    private int code;
}

所以，基本上我想要达到的目标是这样的.

So, basically what I'm trying to achieve is something like this.

TypedQuery<PostalCarrier> query = entityManager.createQuery("SELECT p.carriers FROM PostOffice p 
WHERE p.id = ?1 AND p.carriers.area.code = ?2", PostalCarrier.class);

    query.setParameter(1, postOfficeId);
    query.setParameter(2, areaCode);

我只想从特定的PostOffice获得特定地区代码的PostalCarriers列表. 任何帮助深表感谢！ :)

I only want to get a list of the PostalCarriers at specific area code from a specific PostOffice. Any help is much appreciated! :)

我想我快到了，但是继续出现以下错误:

I think I'm almost there, but keep getting the following error:

 Error compiling the query [SELECT h FROM PostOffice p INNER JOIN p.carriers h 
 WHERE p.id = ?1 AND h.area.code = ?2], line 1, column 71: unknown state or 
 association field [area] of class [com.test.PostalCarrier].

推荐答案

您必须加入PostalCarrier.您无法访问集合中的属性.因此，postalcarrier.area是不正确的.

You must make a join to the PostalCarrier. You can't access a property from a collection. Thus, postalcarrier.area isn't correct.

select postalcarrier from PostOffice p
inner join p.carriers postalcarrier
where p.id = :postOfficeId
and postalcarrier.area.code = :areaCode

这篇关于JPA:查询实体内的可嵌入列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！