@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext.xml"})
public class SPRINGTest {
// @Autowired
// private IPurchaseRequisitionService purchaseRequisitionService;
@Resource
private PurchaseRequisitionItemDao purchaseRequisitionItemDao;
@Test
public void testGetT1() {
Criteria criteria = purchaseRequisitionItemDao.createCriteria();
criteria.setProjection(Projections.sum("quantity"));
List list = criteria.list();
System.out.println(list.size());
}
}
.
首先介绍一下Projections:
org.hibernate.criterion.Projections是 Projection 的实例工厂,我们通过调用setProjection()应用Projections对象进行一个查询.
下面开始操作:
同样需要创建Criteria对象,这对象非常重要,几乎完成了Hibernate中大多的查询功能,配合HQL使用,相应厉害.
- Criteria criteria = session.createCriteria(AccCasherDaySupply.class);
Criteria criteria = session.createCriteria(AccCasherDaySupply.class);
通过Session创建Criteria对象,参数为你要查询的对象类名(这里注意区分大小写).
通过Criteria对象可以使用setProjection的方法,该方法将进行一个Projections的查询.
- criteria.setProjection(****);
criteria.setProjection(****);
接下来就是进行真正的聚合操作部分了,使用Projections对象插入到****的参数中.
Projects对象具有大多聚合的方法,基本上有:rowCount(),avg(),max(),groupProperty(),alias(),property(),sum()...
以sum()为例,如果需要计算某个字段数据的合,将使用sum()方法:
- criteria.setProjection(Projections.sum("字段名"));
criteria.setProjection(Projections.sum("字段名"));
通过以上代码,criteria将得到相应字段名的合.
最后通过criteria.list()得到Projections查询的最终结果.
- criteria.setProjection(Projections.projectionList().add(Projections.property("varName"))
-
.add(Projections.groupProperty("varName")));
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