HQL的新对象 [英] New object with HQL

问题描述

查询：

$ b在HQL查询中创建一个对象，但无法弄清楚我做错了什么。
$ b

  String query =从产品AS产品$ b中选择product.code，SUM（product.price），COUNT（product.code）
 $ b GROUP BY product.code
  

（或者我应该使用新的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：

  public MyCustomList {
 public String code; 
 public BigDecimal price; 
 public int total; 
 
 //构造函数$ b $ public MyCustomList（String code ，String price，int total）{// ... 
  

检索数据：

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

使用Play框架

解决方案

我认为 15.6。 select子句包含了你想要实现的内容：



15.6。 select子句

...

查询可以返回多个对象
和/或属性作为
Object [] 类型的数组：

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

或作为列表：

 选择新列表（母亲，offspr，mate.name）
作为母亲
从内部加入mother.mate作为伴侣
离开外部加入mother.kittens作为offspr 
  

或者 - 假设类 code>
有一个合适的构造函数 - 作为
实际类型安全的Java对象：



  select新家庭（母亲，队友，offspr）
从DomesticCat作为母亲
加入mother.mate成为队友
离开加入mother.kittens as offspr 
  






在您的情况中，您可能想要：



  SELECT new MyCustomList .code，SUM（product.price），COUNT（product.code））从产品AS产品获得
 
 GROUP BY product.code 
  

其中 MyCustomList 不一定是映射的实体。

Trying to create an object from an HQL query, but just can't figure out what i'm doing wrong.

Query:

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

(or should I use new MyCustomList(product.code, SUM(... , even though it's not mapped?) Now I want to cast this returned list into a similar object:

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

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

Retrieving the data:

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

Using Play framework

解决方案

I think that the section 15.6. The select clause covers what you're trying to achieve:

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

In your case, you probably want:

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

Where MyCustomList is not necessarily a mapped entity.

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