从存储库接口检索列表到DTO列表类的最佳方法是什么 [英] What is the best way to Retrieve List from repository interface to DTO list Class

问题描述

DTO软件包中有一个类名DailyElectricity，它包含
max，min，sum，getter和setter的平均值

There is class name DailyElectricity which is in DTO package and it contain max , min, sum , average with getter and setter

public class DailyElectricity implements Serializable {

  private static final long serialVersionUID = 3605549122072628877L;


  private LocalDate date;

  private Long sum;

  private Double average;

  private Long min;

  private Long max;


}

有一个接口，其作用是从数据库获取数据

there is interface which its job is to get data from database

@RestResource(exported = false)
public interface HourlyElectricityRepository 
    extends PagingAndSortingRepository<HourlyElectricity,Long> {
  Page<HourlyElectricity> findAllByPanelIdOrderByReadingAtDesc(Long panelId,Pageable pageable);


  @Query("SELECT max(a.generatedElectricity), sum(a.generatedElectricity),min(a.generatedElectricity),max(a.generatedElectricity)  from HourlyElectricity a where DATE_FORMAT(reading_at,'%Y-%m-%d')=DATE_FORMAT(CURDATE()-1,'%Y-%m-%d') and  panel_id=:panelId")
  List<DailyElectricity> getStaticsDailyElectricity(@Param("panelId")Long panelId);

}

但是当我调用API时，它会给出

it complie without any exception but when i call API it give

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap] to type [com.techtrial.dto.DailyElectricity]

它无法隐藏到dto类

推荐答案

问题是春天没有办法弄清楚如何将查询结果转换为期望的自定义​​对象 DailyElectricity ；为了使这种映射成为可能，您需要做两件事：

The issue is that there is no way for spring to figure out how to convert the result of your query to the custom object DailyElectricity you are expecting from; in order to make this mapping possible you need to do two things:

1. 创建一个构造函数，以便可以创建一个新对象并通过查询的每一行产生的值将其初始化：

1. create a constructor to so you can create a new object and initialize it through the value resulted from each row of you query:

public DailyElectricity (Long max,Long sum,Long min,Double average){    
    this.sum=sum;
    this.average=average;
    this.min=min;
    this.max=max;   
}

然后在<$ c $中对查询使用以下结构c> HourlyElectricityRepository

@Query("SELECT new com.example.DailyElectricity( max(a.generatedElectricity), sum(a.generatedElectricity),min(a.generatedElectricity),avg(a.generatedElectricity))  from HourlyElectricity a where DATE_FORMAT(reading_at,'%Y-%m-%d')=DATE_FORMAT(CURDATE()-1,'%Y-%m-%d') and  panel_id=:panelId")
   List<DailyElectricity> getStaticsDailyElectricity(@Param("panelId")Long panelId);

• 请注意我在查询中使用的软件包名称（ com.example.DailyElectricity ），并确保在测试之前使用与项目相对应的正确软件包名称。


• Please notice the package name I have used in the Query (com.example.DailyElectricity) and make sure you are using the right package name corresponding to you project before testing.

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