Hibernate Group by Criteria Object

Question

我想使用 Hibernate Criteria 实现以下 SQL 查询：

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name <operator> value
GROUP BY column_name

我曾尝试使用 Hibernate Criteria 实现这一点，但没有成功。

谁能给我一个例子，如何使用 Hibernate Criteria 来做到这一点？ 谢谢！

Answer 1

示例请参考这里。重点是使用groupProperty() ，以及Projections类提供的相关聚合函数。

例如 ：

SELECT column_name, max(column_name) , min (column_name) , count(column_name)
FROM table_name
WHERE column_name > xxxxx
GROUP BY column_name

它的等效标准对象是：

List result = session.createCriteria(SomeTable.class)       
                    .add(Restrictions.ge("someColumn", xxxxx))      
                    .setProjection(Projections.projectionList()
                            .add(Projections.groupProperty("someColumn"))
                            .add(Projections.max("someColumn"))
                            .add(Projections.min("someColumn"))
                            .add(Projections.count("someColumn"))           
                    ).list();

Answer 2

GroupBy 在 Hibernate 中使用

这是结果代码

public Map getStateCounts(final Collection ids) {
    HibernateSession hibernateSession = new HibernateSession();
    Session session = hibernateSession.getSession();
    Criteria criteria = session.createCriteria(DownloadRequestEntity.class)
            .add(Restrictions.in("id", ids));
    ProjectionList projectionList = Projections.projectionList();
    projectionList.add(Projections.groupProperty("state"));
    projectionList.add(Projections.rowCount());
    criteria.setProjection(projectionList);
    List results = criteria.list();
    Map stateMap = new HashMap();
    for (Object[] obj : results) {
        DownloadState downloadState = (DownloadState) obj[0];
        stateMap.put(downloadState.getDescription().toLowerCase() (Integer) obj[1]);
    }
    hibernateSession.closeSession();
    return stateMap;
}

Answer 3

你可以使用@Ken Chan 提到的方法，如果你想要一个特定的对象列表，然后添加一行代码，例如：

    session.createCriteria(SomeTable.class)       
                    .add(Restrictions.ge("someColumn", xxxxx))      
                    .setProjection(Projections.projectionList()
                            .add(Projections.groupProperty("someColumn"))
                            .add(Projections.max("someColumn"))
                            .add(Projections.min("someColumn"))
                            .add(Projections.count("someColumn"))           
                    ).setResultTransformer(Transformers.aliasToBean(SomeClazz.class));

List<SomeClazz> objectList = (List<SomeClazz>) criteria.list();

Answer 4

如果您必须使用休眠条件进行group by使用如下所示的projections.groupPropery ，

@Autowired
private SessionFactory sessionFactory;
Criteria crit = sessionFactory.getCurrentSession().createCriteria(studentModel.class);
crit.setProjection(Projections.projectionList()
            .add(Projections.groupProperty("studentName").as("name"))
List result = crit.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP).list(); 
return result;