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")

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

我上了这个课：

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

     // getters setters all args constructor
}

是否可以使用类似以下内容的方法在我的HQL中进行投射：

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可以是接口：

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

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

Answer 2

对于使用自定义类，我首先使用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，您可以在hql中以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对象返回列表

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

2 个答案: