HQL 返回列表<MyClass>而不是列表<对象[]>

Question

在我的总部：

@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")

我想将其返回为：List<MyObject>而不是List<Object[]>

我有这个类：

public class MyObject {
private int age;
private int weight;
// getters setters all args constructor
}

是否可以使用这样的东西在我的 HQL 中投射它：

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

您可以使用投影：

@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可以是接口：

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

Answer 2

用于使用自定义类，我首先使用这些属性创建构造函数

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")

您将从 MyObject 对象返回一个列表