无法将查询的结果转换为休眠中的所需对象答案

【问题标题】：Unable to cast the resultant of the query into desired object in hibernate无法将查询的结果转换为休眠中的所需对象
【发布时间】：2015-07-28 13:34:20
【问题描述】：

我无法将查询结果转换为所需对象 UserTransactionInADay。

这是我的实现

    @Override
            public UserTransactionInADay getTodaysActivity() {
                Date date = new Date();
                String modifiedDate= new SimpleDateFormat("yyyy-MM-dd").format(date);
                Session session = getSession();
                session.clear();
                @SuppressWarnings("unchecked")
                Query qry = session
                .createQuery(
                                "Select u.infoDate, sum(u.totalActiveUsers) as totalActiveUsers, sum(u.plotsVisited) as plotsVisited, sum(u.totalDataSet) as totalDataSet, sum(u.totalAlerts) as totalAlerts, sum(u.totalCropStages) as 

totalCropStages, sum(u.activitiesClosed) as activitiesClosed, sum(u.totalPlotInput) as totalPlotInput, sum(u.totalHarvest) as totalHarvest from UserTransactionInADay u where u.infoDate = ? group by u.infoDate");
            qry.setString(0, modifiedDate);
            List<UserTransactionInADay> userTransactionInADay = qry.list();
            return userTransactionInADay.get(0);
        }

我这样抛出的错误

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.raghu.model.UserTransactionInADay
    com.raghu.dao.CropinDaoImpl.getTodaysActivity(CropinDaoImpl.java:92)
    com.raghu.service.CropinServiceImpl.getTodaysActivity(CropinServiceImpl.java:68)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

【问题讨论】：

标签： sql spring hibernate spring-mvc

【解决方案1】：

我认为您需要稍微回顾一下Hibernate docs。您正在选择一堆数据并尝试将其转换为实体（我假设）集合。

您的查询将返回一个 Object[][]。

假设您的 UserTransactionInADay 具有适当的构造函数，您需要执行以下操作：

"SELECT NEW UserTransactionInADay(u.infoDate, sum(u.totalActiveUsers) 
    AS totalActiveUsers, SUM(u.plotsVisited) AS plotsVisited,
    SUM(u.totalDataSet) AS totalDataSet, SUM(u.totalAlerts) AS totalAlerts,
    SUM(u.totalCropStages) AS totalCropStages, SUM(u.activitiesClosed) AS activitiesClosed,
    SUM(u.totalPlotInput) AS totalPlotInput, SUM(u.totalHarvest) AS totalHarvest) 
FROM UserTransactionInADay u WHERE u.infoDate = ? GROUP BY u.infoDate"

这将再次返回 UserTransactionInADay 对象，假设该类型有适当的构造函数。

【讨论】：