hibernate - 带有 HQL 的新对象

Question

试图从 HQL 查询创建一个对象，但无法弄清楚我做错了什么。

询问:

String query = "SELECT product.code, SUM(product.price), COUNT(product.code)
from Product AS product
GROUP BY product.code"

(或者我应该使用 new MyCustomList(product.code, SUM(... ，即使它没有被映射？)
现在我想把这个返回的列表转换成一个类似的对象:

class MyCustomList{
  public String code;
  public BigDecimal price;
  public int total;

  // Constructor
  public MyCustomList(String code, String price, int total){ //...

检索数据:

// This throws ClassCastException    
List<MyCustomList> list = MyClass.find(query).fetch();

使用 Play 框架

Answer 1

我认为该部分15.6. The select clause涵盖您要实现的目标:

15.6. The select clause

...

Queries can return multiple objects and/or properties as an array of type Object[]:

select mother, offspr, mate.name
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

Or as a List:

select new list(mother, offspr, mate.name)
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

Or - assuming that the class Family has an appropriate constructor - as an actual typesafe Java object:

select new Family(mother, mate, offspr)
from DomesticCat as mother
    join mother.mate as mate
    left join mother.kittens as offspr

在您的情况下，您可能想要:

SELECT new MyCustomList(product.code, SUM(product.price), COUNT(product.code))
from Product AS product
GROUP BY product.code

哪里 MyCustomList不一定是映射实体。