Hibernate Group by Criteria Object

Question

我想用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

我试图用Hibernate Criteria来实现它,但它没有成功.

谁能给我一个例子,说明如何使用Hibernate Criteria？谢谢!

Answer 1

请参考此示例.主要用于使用Projections类groupProperty()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

其等效标准对象是:

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

这是生成的代码

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,那么在那之后添加一行代码,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();