本文介绍了对于COUNT个查询,JPA EntityManager.getSingleResult()返回什么?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
EntityManager.getSingleResult()
返回COUNT查询返回什么?
What does EntityManager.getSingleResult()
return for a COUNT query?
那么.. foo的确切运行时类型是什么?
So.. what is the precise runtime type of foo?
Object foo = em.createQuery("SELECT COUNT(t) FROM com.company.Thing t WHERE prop = :param")
.setParameter("param", value).getSingleResult();
推荐答案
COUNT(t)特别返回java.lang.Long.当它在这种情况下独自出现时,将按原样返回.
COUNT(t) specifically returns java.lang.Long. When its appears on its own in this context it is returned as-is.
(在其他情况下,由COUNT生成的Long可能会被包装,但不是今天.)
(In other contexts the Long generated by COUNT may be wrapped, but not today.)
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