从JPA Query.getResultList（）映射到自定义的TO

问题描述

我有一个表格，里面有四列id，名称，颜色和形状。表中的

条目为：

  
您使用的HQL将返回 List< Object []>  code>是位置0中 shape 的数组，而位置1中是 name 。
 
 
 
您可以使用：
  List fruitList = s.createQuery（
select f.shape as shape，f.name （f.shape =：shape;）
 .setParameter（shape，paramShape）
 .setResultTransformer（Transformers.aliasToBean（FruitSearchTO.class））
 .list （）; 
 FruitSearchTOdto =（FruitSearchTO）fruitList .get（0）; 
  
或者，如果 FruitSearchTO 具有适当的构造函数：，你也可以通过选择新的FruitSearchTO（f.shape，f.name）来实现。  
 
 
查看关于HQL的Hibernate Reference章节，特别是 15.6 选择子句一章。
 
I have a table fruit with four columns id, name, color, shape.
entries in the table would be:
1, apple, red, round
2, banana, yellow, long
3, tomato, red, round
4, orange, orange, round
Now I made an entity class Fruit mapped to above table.
@Entity
@Table(name="fruit")
public class Fruit implements Serializable {

@Id
@Column(name="ID")
String id;

@Column(name="NAME")
String name;

@Column(name="COLOR")
String color;

@Column(name="SHAPE")
String shape;

//getters/setters goes here
}
In my DAO class, the code is:
String myQuery = "Select f.shape, f.name from Fruit f where f.shape = :shape";
Query query = this.em.createQuery(myQuery);
query.setParameter("shape", "round");
As obvious, running above query will return 3 rows. 
I have a simple TO class FruitSearchTO
class FruitSearchTO
{
  String shape;
  String name;

  //getters/setters here
}
This TO complies with the rows returned by my query.
But in my DAO running something like:
List<FruitSearchTO> fruitList = new ArrayList<FruitSearchTO>();
fruitList = query.getResultList();
is throwing exception java.lang.ClassCastException: [Ljava.lang.Object; incompatible with FruitSearchTO]
Where am I going wrong and what is the solution to this ?
 解决方案 
The HQL you're using will return a List<Object[]>, each element of the List being an array with shape in position 0 and name in position 1. 
You can make the HQL return a List<FruitSearchTO> using an AliasToBeanResultTransformer: 
List fruitList = s.createQuery(
  "select f.shape as shape, f.name as name from Fruit f where f.shape = :shape;")
  .setParameter("shape", paramShape)
  .setResultTransformer( Transformers.aliasToBean(FruitSearchTO.class))
  .list();
FruitSearchTOdto = (FruitSearchTO) fruitList .get(0);
Alternatively, if FruitSearchTO has an appropriate constructor:, you can also achieve this with select new FruitSearchTO(f.shape, f.name). 
Take a look at the Hibernate Reference chapter on HQL, particularly 15.6 The select clause chapter.
                        
这篇关于从JPA Query.getResultList（）映射到自定义的TO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！