jpa-2.0 - JPA 2 无显式选择且隐式一冷未确定

Question

我正在尝试获取某个文件夹中的所有用户，该用户是在特定日期之后创建的。用户和文件夹之间的关系位于单独的表中。

这是我提出的查询，但它引发了异常

No explicit selection and an implicit one cold not be determined

代码

@Override
public List<RetailPostUserTbl> getNewUsersForSiteSince( Date date, Integer siteId )
{
    List<RetailPostUserTbl> toReturn = new ArrayList<RetailPostUserTbl>();
    EntityManager em = getEntityManager();
    CriteriaBuilder cb = em.getCriteriaBuilder();

    Class<RpUserFolderMapTbl> userFolderPC = userFolderMapDAO.getPersistentClass();

    CriteriaQuery<RpUserFolderMapTbl> mapQuery = cb.createQuery( userFolderPC );
    Root<RpUserFolderMapTbl> root = mapQuery.from( userFolderPC );
    Path<Integer> folderIdPath = root.get( RpUserFolderMapTbl_.folder ).get( FolderTbl_.folderId );

    Predicate folderCondition = cb.equal( folderIdPath, siteId );

    Subquery<RetailPostUserTbl> rpSubQ = mapQuery.subquery( persistentClass );
    Root<RetailPostUserTbl> subQRoot = rpSubQ.from( persistentClass );
    Path<UserTbl> userPath = subQRoot.get( RetailPostUserTbl_.user );
    Path<Date> userCreatedPath = userPath.get( UserTbl_.userCreateDate );
    Predicate userCreateDateCondition = cb.greaterThanOrEqualTo( userCreatedPath, date );
    rpSubQ.where( userCreateDateCondition );

    mapQuery.where( cb.and( folderCondition, cb.exists( rpSubQ ) ) );

    TypedQuery<RpUserFolderMapTbl> query = em.createQuery( mapQuery );
    List<RpUserFolderMapTbl> results = query.getResultList();
    for ( RpUserFolderMapTbl result : results )
    {
        RetailPostUserTbl rpuser = result.getUser().getRetailPostUser();
        toReturn.add( rpuser );
    }
    return toReturn;
}

有人知道为什么这不起作用吗？

Answer 1

您还应该为“子查询”设置显式选择。

rpSubQ.select(subQRoot);