HQL 返回 List<MyClass> 而不是 List<Object[]>

Question

打印我的 HQL：@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[]>我有这门课：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

为了使用自定义类，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 中你可以按照相同的值顺序调用这个构造函数

@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