如何从休眠中的类型化查询返回不是实体的对象列表？ [英] how to return a list of object which is not entity from a typed query in hibernate?

问题描述

我需要从实体类Employee中提取一些字段，并添加一些额外的硬编码字段，并使用GROUP BY子句返回结果。

I need to pull few fields from entity class Employee and add few extra hard coded field and return the result using GROUP BY clause.

下面是我尝试过的代码：

Below is the code I tried:

String query = "SELECT emp.category, emp.salary  0 as somevalue, 0 as dummy FROM employee emp "
                + "WHERE emp.date = :date AND emp.class = :class AND emp.classificationDetail.shortDescription = :classificationType GROUP BY emp.category";

        TypedQuery<CustomEmployee> typQuery = entityManager.createQuery(query, CustomEmployee.class);

        typQuery.setParameter("date", req.getDate());
        typQuery.setParameter("class", req.getClass());


        return typQuery.getResultList();

但是我遇到了一个例外，即无法使用请求的结果类型为多个返回的查询创建TypedQuery。

But I am getting exception that Cannot create TypedQuery for query with more than one return using requested result type.

如何实现这一目标。
谢谢。

How to achieve this. Thanks.

推荐答案

首先检查此部分： emp.salary 0作为somevalue 。这应该是 emp.salary作为某值或 0作为某值，但不能两者都使用。

First check this part: emp.salary 0 as somevalue. This should be either emp.salary as somevalue or 0 as somevalue, but not both.

定义如下所示的类（为了简短起见；我使用公共属性，但可以根据需要更改它）：

Define a class like following (to keep it short; I use public properties, but you can change it if you want):

public class CustomEmployee {
    public String category;
    public Double salary;
    public Double dummy;
    ...
}

在查询中使用它的方式如下：

The use it in the query as follows:

String query = "SELECT new mypackage.CategorySalary( " +
    "    emp.category, " +
    "    emp.salary as somevalue, " +
    "    0 as dummy " +
    ") from ...  " +
    "WHERE ...  ";

TypedQuery<CustomEmployee> typQuery = entityManager.createQuery(query, CustomEmployee.class);

这篇关于如何从休眠中的类型化查询返回不是实体的对象列表？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！