HQL return 列表<MyClass> 而不是列表<Object[]>

Question

在我的 HQL 中：

@Query("SELECT count(a.age) as age, count(w.weight) as weight from animals a inner join weight_table w on a.id = w.id")

我想要 return 它是： List<MyObject> 而不是 List<Object[]>

我有这个class:

public class MyObject {
     private int age;
     private int weight;

     // getters setters all args constructor
}

是否可以使用如下方式在我的 HQL 中进行转换：

SELECT new.com.cs.MyObject(age, weight) count(a.age) as age, count(w.weight) as weight from animals a inner join weight_table w on a.id = w.id

Answer 1

您可以使用 projection:

@Query("SELECT count(a.age) as age, count(w.weight) as weight from animals a inner join weight_table w on a.id = w.id")
public List<MyObject> myMethodNameDescribingFunctionality();

其中 MyObject 可能是一个接口：

public interface MyObject {
    @Value("#{target.age}")
    int age();

    @Value("#{target.weight}")
    int weight;
}

Answer 2

为了使用自定义 class 我首先使用为这些属性创建一个构造函数

public class MyObject {
     private int age;
     private int weight;
     public  MyObject(int age , int weight) {
         this.age=age;
         this.weight = weight; 
     }
}

之后，在 hql 中，您可以按相同的值顺序调用此构造函数

@Query("SELECT new com.packagename.MyObject(count(a.age), count(w.weight)) from animals a inner join weight_table w on a.id = w.id")

您将 return 来自 MyObject 对象的列表

HQL return 列表<MyClass> 而不是列表<Object[]>

HQL return List<MyClass> instead List<Object[]>

java

spring

jpa

hql