JPA 2没有明确的选择，也没有确定隐含的一种感冒 [英] JPA 2 No explicit selection and an implicit one cold not be determined

问题描述

我正在尝试为某个日期之后在其中创建用户的文件夹获取所有用户。用户和文件夹之间的关系位于单独的表中。

I am trying to fetch all users for a folder where the user was created after a certain date. the relationship between the user and the folder lives in a seperate table.

这是我提出的查询，但它可以解决异常情况

This is the query I came up with but it thorws the exception

没有明确的选择和不确定的隐患

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;
}

有人知道为什么这行不通吗？

Anyone know why this is not working?

推荐答案

还应该为子查询显式设置选择。

You should set explicitly selection also for "subqueries".

rpSubQ.select(subQRoot);

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