Question

尝试从HQL查询创建一个对象，但却无法弄清楚我做错了什么。

查询：

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

（或者我应该使用新的MyCustomList（product.code，SUM（...，即使它没有映射？）现在我想将这个返回的列表转换为类似的对象：

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15.6. The select clause部分涵盖了您要实现的目标：

15.6. The select clause

...

查询可以返回多个对象   和/或作为类型数组的属性   Object[]：
select mother, offspr, mate.name
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr
或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
或者 - 假设班级Family 有一个合适的构造函数 - 作为实际的类型安全Java对象：
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

MyCustomList不一定是映射实体。

Answer 2

我知道这是一篇旧帖子，但你也可以用于HQL：

Query query = session.createQuery("SELECT code AS code FROM Product");

或者这个用于SQL：

Query query = session.createSQLQuery("SELECT code AS code FROM Product");

使用：

query.setResultTransformer(Transformers.aliasToBean(MyCustomList.class));

HQL的新对象

2 个答案:

15.6. The select clause