hibernate - 如何使用 Spring Data/JPQL 从子类实体属性中进行选择？

Question

我需要查询子类的属性。以下是涉及的实体:

@Entity
@Data
public class Course {

    @Id
    private Long id;
    
    @ManyToOne
    @JoinColumn(name = "personId")
    private Person person;

}

@Entity
@Data
@Inheritance(strategy = InheritanceType.JOINED)
public class Person {

    @Id
    private Long id;

    private String name;

}

@Entity
@Data
@EqualsAndHashCode(callSuper=true)
public class Student extends Person {

    @ManyToOne
    @JoinColumn(name="studentTypeId")
    private StudentType studentType;
            
}

@Entity
@Data
public class StudentType {

    @Id
    private Long id;
    
    @Convert(converter = StudentTypeConverter.class)
    private StudentTypeEnum name;
    
    @RequiredArgsConstructor
    @Getter
    @ToString
    public static enum StudentTypeEnum {
        GRADUATE("Graduate");
        
        private final String name;
        
    }

}

我正在尝试使用 Spring 数据存储库进行查询:

public interface CourseRepository extends Repository<Course>  {
    
    List<Course> findByCoursePersonStudentTypeName(@Param("studentTypeName") String studentTypeName);
}

但这不起作用。它会生成一条错误，指出No property StudentTypeName found for Person!。这是有道理的，因为该属性仅存在于 Student 上。

我如何编写此方法(最好)或使用 JPQL 按学生类型查找类(class)？

Answer 1

这个怎么样:

@Query("select c from Course c join c.person as p where UPPER(p.studentType.name) = UPPER(?1)")
List<Course> findByCoursePersonStudentTypeName(String studentTypeName);

这使用了 Hibernate 的一项称为隐式转换的功能。