java - 未正确获取查询结果

Question

我写了以下内容query。

select 
  count (distinct asset.assetId) 
from 
  Asset asset 
  left join asset.assetTitles title  
  left join asset.distTypes distTypes
where 
  title.program.id in (:progIdParam) 
  and distTypes in (:lkpDistTypeId) 
  and asset.active = 1
  and asset.isShow = 1
  and asset.classification = 'Internal Use'

我称之为：

 private Long assetTitleListForIp = 0L;

 assetTitleListForIp = (Long)entityManager
      .createQuery(query)                                 
      .setParameter("progIdParam",progId)
      .setParameter("lkpDistTypeId",LookupValueEnum.DIST_TYPE_INTL_PRODUCTION.getLkpId())
      .getSingleResult();

如果我在 Eclipse 控制台中触发查询并在 DB 中运行它，它将显示计数为 1。但在应用程序中，对于assetTitleListForIp，它将值分配为零。我没有得到我所犯的小错误。有人可以帮忙吗？

Answer 1

看起来assetTitleListForIp是场。我怀疑您的问题与查询本身无关。可能的问题：

• 查询全部运行，您看到的只是初始值assetTitleListForIp
• assetTitleListForIp在执行查询的方法中被局部变量屏蔽
• 您正在assetTitleListForIp从持有该字段的对象的其他实例中读取该字段。

Answer 2

可能你有铸造问题。getSingleResult()不直接转换为Long. 尝试得到如下结果：

Object countObj=entityManager.createQuery(
               "select count (distinct asset.assetId) from Asset asset left join "+
               "asset.assetTitles title  left join asset.distTypes distTypes where "+
               "title.program.id in (:progIdParam) and distTypes in (:lkpDistTypeId) "+
               "and asset.active =1 and asset.isShow = 1 and asset.classification "+
               "='Internal Use'")
               .setParameter("progIdParam",progId)
               .setParameter("lkpDistTypeId",
               LookupValueEnum.DIST_TYPE_INTL_PRODUCTION.getLkpId())
               .getSingleResult();

Long count=Long.valueOf(""+countObj);
assetTitleListForIp=count;