为 TypedQuery 指定的类型与查询 return 类型 [class java.lang.Double] 不兼容

Question

我正在尝试使用 j2ee 和 hibernate 在两个实体之间建立连接。但是我收到以下错误：

java.lang.IllegalArgumentException: Type specified for TypedQuery is incompatible with query return type [class java.lang.Double]

这是我正在尝试处理的查询

Query query = entityManager
                .createQuery("SELECT avg(responseEnd - responseStart)  FROM QualiteDeService q  join q.test",QualiteDeService.class );

这些是实体：

    @Entity
    public class QualiteDeService {

        private int id_qualite_service;
            private Test test;

        @Id    
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        public int getId_qualite_service() {
            return id_qualite_service;
        }
        @ManyToOne
        @JoinColumn(name = "id_test", referencedColumnName = "id_test", insertable = false, updatable = false)
        public Test getTest() {
            return test;
        }
        public void setTest(Test test) {
            this.test = test;
        }
    }


    @Entity
    public class Test implements Serializable{
    private int id_test;
private int note;

    @Id    
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    public int getId_test() {
        return id_test;
    }
    public void setId_test(int id_test) {
        this.id_test = id_test;
    }
    }

Answer 1

查询 return 类型需要与要在其中转换它的实体对象兼容。更新您的代码

entityManager.createQuery("SELECT avg(responseEnd - responseStart)  FROM QualiteDeService q  join q.test",Double.class );

为 TypedQuery 指定的类型与查询 return 类型 [class java.lang.Double] 不兼容

Type specified for TypedQuery is incompatible with query return type [class java.lang.Double]

hibernate

hql

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