[英]JPA: Return custom object using projection
I have this code in SponsorRepository
which extends JpaRepository<Sponsor, Long>
...我在SponsorRepository
中有这段代码,它扩展JpaRepository<Sponsor, Long>
...
@Query(value = "SELECT s.fundraiser_name, d.amount_in_pence/100" +
" FROM sponsor_form s INNER JOIN donation d ON s.id = d.sponsor_form_id " +
"WHERE d.charity_id = :charityId ORDER BY d.amount_in_pence*100 DESC LIMIT 5", nativeQuery =
true)
public List<Sponsor> findTopFiveSponsors(@Param("charityId") Long charityId);
The problem is that when running the server it gives me an error saying that the id was not found.问题是,在运行服务器时,它给了我一个错误,说找不到 id。 I researched into this and found that I am making the function return a list of sponsors, even though the query itself is return a fundraiser name and amount.我对此进行了研究,发现我正在让 function 返回赞助商列表,即使查询本身返回筹款人名称和金额。 Also, JPA cannot map this into a list of sponsor.此外,JPA 不能将 map 列入赞助商名单。 I was advised to use JPA projection.有人建议我使用 JPA 投影。 What are the steps I need to take to do so?我需要采取哪些步骤才能这样做? Would projection be the solution or a RestController
?投影是解决方案还是RestController
?
Create new protection interface for your result tuple:为您的结果元组创建新的保护接口:
public interface SponsorProjection {
String getName();
Long getAmount();
}
Then add aliases and change the return type:然后添加别名并更改返回类型:
@Query(value = "SELECT s.fundraiser_name as name, d.amount_in_pence/100 as amount " +
"FROM sponsor_form s INNER JOIN donation d ON s.id = d.sponsor_form_id " +
"WHERE d.charity_id = :charityId " +
"ORDER BY d.amount_in_pence * 100 DESC LIMIT 5", nativeQuery = true)
public List<SponsorProjection> findTopFiveSponsors(@Param("charityId") Long charityId);
Your controller will look like this:您的 controller 将如下所示:
@RestController
public class SponsorController {
@Autowired
private SponsorRepository repo;
@GetMapping(path = "/findTopFiveSponsors")
public ResponseEntity<?> get(@Param("charityId") Long charityId) {
return ResponseEntity.ok(repo.findTopFiveSponsors(charityId));
}
}
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