我们如何使用旧版本的Hibernate（〜2009）计算行数？

Question

例如，如果我们有一个表格Books，那么我们如何计算休眠状态下的图书记录总数？

Answer 1

对于旧版本的Hibernate（<5.2）：假设类名是Book：return (Number) session.createCriteria("Book")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .setProjection(Projections.rowCount())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .uniqueResult();它至少是一个Number，很可能是一个Long。

Answer 2

在Java中，我通常需要返回int并使用以下形式：int count = ((Long)getSession().createQuery("select count(*) from Book").uniqueResult()).intValue();

Answer 3

如果您使用的是Hibernate 5+，则查询将被修改为Long count = session.createQuery("select count(1) from&nbsp; Book")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .getSingleResult();或者如果您需要TypedQueryLong count = session.createQuery("select count(1) from&nbsp; Book",Long.class)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .getSingleResult();