java计数休眠和命名查询

Question

我想使用NamedQueries计算表中的元素

NamedQuery是：

@NamedQuery(name = Advertisement.countBySubcategoryList, query = "select count(*) from  Advertisement where subcategoryId IN (:subcategoryId)")

以及：

public static final String countBySubcategoryList = "Advertisement.countBySubcategoryList";

在模型中，我使用：

List<Advertisement> advertisements = session.getNamedQuery(Advertisement.countBySubcategoryList)
            .setParameterList("subcategoryId", subcategoryIds)
            .list();

如何从查询中获取计数值

Answer 1

您的查询应该类似于

select count(a) from Advertisement a where a.subcategoryId IN (:subcategoryId)

你应该这样称呼它

Long count = (Long)session.getNamedQuery(Advertisement.countBySubcategoryList)
            .setParameterList("subcategoryId", subcategoryIds)
            .uniqueResult();

编辑

对于这种类型的查询，4之前的Hibernate版本返回了Integer，而不是Long

Answer 2

如果您是hibernate版本，您甚至可以尝试此功能<；四,

int count = ((Number)em.createNamedQuery("Advertisement.countBySubcategoryList").getSingleResult()).intValue();

如果您是hibernate版本>；=4 . @马里克是对的

Long count = (Long)session.getNamedQuery(Advertisement.countBySubcategoryList) .setParameterList("subcategoryId", subcategoryIds) .uniqueResult();