스프링부트 native Query에러 No converter found capable of converting from type

공부 배경

협업을 하면서 나의 게시글 조회 기능을 제작해야 했다.
나의 게시글 조회를 하기 위해서는 스프링부트에서 nativeQuery를 사용해야했는데, 문제는 에러가 생기면서 쿼리의 값이 불러오지 않는 에러가 생겼다.

데이터베이스 상에서는 쿼리가 잘 작동되어 값을 가져온것을 볼 수 있다.

에러 내용

No converter found capable of converting from type

2022-04-23 23:23:42.073 ERROR 19704 --- [io-8080-exec-10] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap] to type [dev.sideproject.momo.model.UserPost]] with root cause

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [org.springframework.data.jpa.repository.query.AbstractJpaQuery$TupleConverter$TupleBackedMap] to type [dev.sideproject.momo.model.UserPost]
	at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:322) ~[spring-core-5.3.18.jar:5.3.18]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) ~[spring-core-5.3.18.jar:5.3.18]
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:175) ~[spring-core-5.3.18.jar:5.3.18]

설정했던 코드

Repository

native 쿼리 넣기

public interface UserRepository extends CrudRepository <UserEntity, Long> {


  @Query(
            nativeQuery = true,
            value = "SELECT p.topic, p.content, p.create_at\n" +
                    "FROM user_momo u\n" +
                    "    INNER JOIN post p on u.id = p.user_id\n" +
                    "where u.id = :id"
    ) List<UserPost> findByUserPost(@PathVariable("id") Long id);

}

UserService

public interface UserService {

    UserDto create(UserDto dto);
    Collection<UserDto> readAll();
    UserDto read(Long id);
    boolean update(UserDto dto, Long id);
    boolean delete(Long id);

   Collection<UserPost> findByUserPost(Long id);     // 추가! 
  

}

JPA UserService

@Service
public class JpaUserService implements UserService{
    private final UserRepository userRepository;


    public JpaUserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }


   

   @Override
    public Collection<UserPost> findByUserPost(Long id) {
        List<UserPost> userPostList = this.userRepository.findByUserPost(id);
        userPostList.forEach(
                userPost -> userPostList.add(
                        new UserPost(
                                userPost.getTopic(),
                                userPost.getContent(),
                                userPost.getCreateAt()
                        )
                )
        );


     return userPostList;
    }


}

UserPost

쿼리로 불러올 형식의 DTO 추가

public class UserPost {
    private String topic;
    private String content;
    private Instant createAt;

    public UserPost() {
    }

    public UserPost(String topic, String content, Instant createAt) {
        this.topic = topic;
        this.content = content;
        this.createAt = createAt;
    }

    public String getTopic() {
        return topic;
    }

    public void setTopic(String topic) {
        this.topic = topic;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Instant getCreateAt() {
        return createAt;
    }

    public void setCreateAt(Instant createAt) {
        this.createAt = createAt;
    }
}

UserController

@RestController
@RequestMapping("api/user")
public class UserController {

    private final UserService userService;

    public UserController(UserService userService) {
        this.userService = userService;
    }

  

//내가 쓴글 불러오기
    @GetMapping("{id}/post")
    public ResponseEntity<Collection<UserPost>> userPost(
            @PathVariable Long id){

        Collection<UserPost> result = this.userService.findByUserPost(id);
        return  ResponseEntity.ok(result);
    }

해결방법

UserPost를 삭제 UserPost 대신 인터페이스를 생성하여 값을 불러오도록 하였다.

UserPostInterface

public interface UserPostInterface {

    String getTopic();
    String getContent();
    Instant getCreate_At();

}

바뀐 Repository

    @Query(
            nativeQuery = true,
            value = "SELECT p.topic, p.content, p.create_at\n" +
                    "FROM user_momo u\n" +
                    "    INNER JOIN post p on u.id = p.user_id\n" +
                    "where u.id = :id"
    ) List<UserPostInterface> findByUserPost(@PathVariable("id") Long id);