Select 实体另一个属性的属性

Question

目前我有三个实体 Country、Office 和 User，其中 Country.gov 是 Office 类型，Office.holder 是 User。 Country 是 Country.gov 的拥有方，Office 是 Office.holder.

的拥有方

现在我想使用 Office.holder 上的 LEFT JOIN 使用国家/地区的属性来获取 Country.gov，例如 SELECT c.gov o FROM Country c LEFT JOIN FETCH c.gov LEFT JOIN FETCH c.gov.holder WHERE c.countryKey = :countryKey，但这不起作用，它抛出异常：

org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list 
[FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=null,role=dev.teamnight.game.entities.Country.gov,tableName=office,tableAlias=office1_,origin=country country0_,columns={country0_.gov_id,className=dev.teamnight.game.entities.Office}}] 
[SELECT c.gov FROM dev.teamnight.game.entities.Country c LEFT JOIN FETCH c.gov LEFT JOIN FETCH c.gov.holder WHERE c.countryKey = :countryKey]

Answer 1

您可以稍微简化一下查询：

List<Office> calls = entityManager.createQuery(
    "select o " +
    "from Country c " +
    "join c.gov o " +
    "left join fetch o.holder " +
    "where c.countryKey = :countryKey ", Office.class )
.setParameter( "countryKey", countryKey )
.getResultList();

有关其他说明，请参阅 this section 休眠文档。

Select 实体另一个属性的属性

Select attribute of another attribute of entity

spring

hibernate

jpa

jpql