Java jdbcTemplate通过邮递员打印外键值

我在实体课以下

class Task {
@Id
@GeneratedValue
Long id;

Integer plannedEffort;
Integer actualEffort;
Integer workCompletedPercent;

//foreign key field
@ManyToOne
Resource createdBy;

@ManyToOne
Project project;

@ManyToOne
Resource assignedTo;

@ManyToOne
Task parentTaskCode
}

这就是服务方式

public List<TaskDTO> getAllResourcesTaskReport(){
log.info(" Service getAllResourcesTaskReport");
String sql="select id,sum(actual_effort) as actual_effort,um(planned_effort) as planned_effort,(actual_effort/planned_effort*100) as work_completed_percent,assigned_to_id,created_by_id,parent_task_code_id,project_id from task group by assigned_to_id";

List<TaskDTO> list  = getJdbcTemplate().query(sql,new BeanPropertyRowMapper(TaskDTO.class));
return list;

}

请告诉我为什么外键字段的值为空

  [
  {
    "id": 1181,
    "plannedEffort": 240,
    "actualEffort": 177,
    "workCompletedPercent": 83,
    "createdBy": null,
    "project": null,
    "assignedTo": null,
    "parentTaskCode": null,
    "activity": null
  }
]