[개발일지#008] 타임라인 등록/삭제/조회API 구현

[사용기술]

Java, Spring Boot, Spring JPA, MySQL

 

[만들려는 것]

책을 위한 SNS.

 

[오늘 하려는 것]

타임라인(Member) 등록/조회 API 개발

 

---

 

TimelineApiController.java

1. 타임라인 등록

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

    //타임라인 등록
    @PostMapping
    public CreateTimelineResponse saveTimeline(@RequestBody CreateTimelineRequest request){
        Book createBook = new Book(request.getBook().getIsbn(), request.getBook().getTitle()
                                ,request.getBook().getAuthor(), request.getBook().getPublisher());
        Integer timelineSeq = timelineService.createTimeline(request.getMemberSeq(), createBook, request.getContents());
        return new CreateTimelineResponse(timelineSeq);
    }

	//코드생략//



}

• Member API와 비슷한 구조로 CreateTimelineRquest 객체를 활용해 요청 파라미터를 넘겨 받아 생성하고 CreateTimelineResonse 객체로 반환해줌.

 

CreateTimelineRquest.java

package seulgi.bookbookclub.dto;

import lombok.Data;
import lombok.Getter;
import lombok.Setter;
import seulgi.bookbookclub.domain.Book;

@Getter
@Setter
public class CreateTimelineRequest {

    private Integer memberSeq;
    private Book book;
    private String contents;

}

 

 

CreateTimelineResonse.java

package seulgi.bookbookclub.dto;


import lombok.Data;
import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class CreateTimelineResponse {

    private Integer timelineSeq;

    public CreateTimelineResponse(Integer timelineSeq) {
        this.timelineSeq = timelineSeq;
    }
}

 

 

 

---

TimelineApiController.java

2. 타임라인 (논리)삭제

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.hibernate.sql.Delete;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.dto.TimelineDto;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

    //코드생략//
    
    //타임라인 삭제
    @PostMapping("/delete/{timelineSeq}")
    public void deleteTimeline(@PathVariable("timelineSeq") Integer timelineSeq){
        timelineService.deleteTimeline(timelineSeq);
    }

}

• 논리 삭제라서 상태값만 변경해줌.

 

TimelineService.java

package seulgi.bookbookclub.service;

import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.Member;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.repository.BookRepository;
import seulgi.bookbookclub.repository.MemberRepository;
import seulgi.bookbookclub.repository.TimelineRepository;

import java.util.List;
import java.util.stream.Collectors;

@Service
@Transactional(readOnly = true)
@RequiredArgsConstructor
public class TimelineService {

    private final TimelineRepository timelineRepository;
    private final MemberRepository memberRepository;
    private final BookRepository bookRepository;
    private final FollowService followService;

    //코드생략//
    
    //글 삭제
    @Transactional
    public void deleteTimeline(Integer timelineSeq){
        Timeline timeline = timelineRepository.findById(timelineSeq);
        if (timeline == null){
            throw new IllegalArgumentException("해당 글이 존재하지 않습니다.");
        }
        timeline.delete();
    }


}

 

Timeline.java

package seulgi.bookbookclub.domain;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.NoArgsConstructor;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import java.time.LocalDateTime;

import static jakarta.persistence.FetchType.*;

@Entity
@Getter
@EntityListeners(AuditingEntityListener.class)
@NoArgsConstructor
public class Timeline {


    //코드생략//

    //논리 삭제
    public void delete() {
        this.state = State.INACTIVE;
    }
}

• 레파지토리에서 쿼리로 동작하지 않고 변경감지 기능(?)을 이용해서 엔티티에서 상태만 변경해줌.

 

[테스트 성공]

 

 

---

TimelineApiController.java

3. 특정회원이 쓴 타임라인 글 조회

ver1. 엔티티 그대로 반환하기 

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.dto.TimelineDto;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

	//코드생략//

    //특정회원이 업로드 한 타임라인 조회
    @GetMapping("/upload/{memberSeq}")
    public Result timelinesByMember(@PathVariable("memberSeq") Integer memberSeq){
        List<Timeline> findTimelines =  timelineService.getMemberTimelines(MemberSeq);
        List<Timeline> collect = findTimelines.stream().map(t -> new Timeline(t.getMember(), t.getBook(), t.getContents()))
                .collect(Collectors.toList());
        return new Result(collect);
    }

}

 

TimelineRepository.java

package seulgi.bookbookclub.repository;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.State;
import seulgi.bookbookclub.domain.Timeline;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Repository
public class TimelineRepository {

    @PersistenceContext
    private EntityManager em;

	//코드생략//

    //특정회원이 업로드 한 타임라인 조회
    public List<Timeline> findTimelinesByMember(Integer memberSeq) {
        return em.createQuery("SELECT t FROM Timeline t WHERE t.member.memberSeq = :memberSeq AND t.state = :state ORDER BY t.createdDate DESC", Timeline.class)
                .setParameter("memberSeq", memberSeq)
                .setParameter("state", State.ACTIVE)
                .getResultList();
    }


}

 

 

 

[에러 발생]

@ManyToOne 관계가 포함된 엔티티를 그대로 반환하면 아래와 같은 에러를 뱉어 낸다.

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: seulgi.bookbookclub.dto.Result["data"]->java.util.ArrayList[0]->seulgi.bookbookclub.domain.Timeline["member"]->seulgi.bookbookclub.domain.Member$HibernateProxy$yv1BEjjx["hibernateLazyInitializer"]) at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77) ~[jackson-databind-2.18.2.jar:2.18.2]

이 에러는 한마디로 객체를 JSON형식으로 변환할 때 생기는 문제이다. 

구체적으로 말하면 지연로딩 기능 때문에 발생하는데, 하이버네이트는 데이터베이스에서 필요한 데이터를 바로 다 가져오지 않고, 나중에 필요할 때 가져오는 방식(=지연로딩)으로 작동하고 아직 가져오지 않은 데이터를 대신하는 가짜객체(=프록시객체)를 만들어 놓음. 

문제는 Jackson라이브러리(JSON 변환라이브러리)가 이 프록시객체를 제대로 변환하지 못하다보니 생기는 에러!

그래서 아래와 같이 아래 500에러를 뱉어 버린다.

 

 

Ver2. DTO 객체 생성하여 반환하기

해결방법은 몇 가지가 있는데 일단 DTO객체 생성하여 반환하는 방법으로 풀어보자.

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.dto.TimelineDto;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

    //코드생략//

    //특정회원이 업로드 한 타임라인 조회
    @GetMapping("/upload/{memberSeq}")
    public Result timelinesByMember(@PathVariable("memberSeq") Integer memberSeq){
        List<Timeline> findTimelines =  timelineService.getMemberTimelines(MemberSeq);
        List<TimelineDto> collect = findTimelines.stream()
                .map(t -> new TimelineDto(
                        t.getTimelineSeq(),
                        t.getMember().getMemberId(),
                        t.getMember().getNickname(),
                        t.getLikes(),
                        t.getBook().getTitle(),
                        t.getBook().getAuthor(),
                        t.getContents(),
                        t.getCreatedDate()))
                .collect(Collectors.toList());
        return new Result(collect);
    }



}

• 기존에는 엔티티 객체인 Timeline객체를 그대로 반환했었는데 이번에는 TimelineDto 객체를 생성하여 반환타입을 바꿔주었음.

 

 

TimelineDto.java

package seulgi.bookbookclub.dto;


import lombok.AllArgsConstructor;
import lombok.Data;

import java.time.LocalDateTime;
import java.util.List;
import java.util.stream.Collector;

@Data
@AllArgsConstructor
public class TimelineDto {

    private Integer timelineSeq;
    private String memberId;
    private String nickName;
    private Integer likes;
    private String bookTitle;
    private String bookAuthor;
    private String publisher;
    private LocalDateTime createdDate;

}

• 객체타입은 없고 모두 기본 타입으로 변경해주었음.

 

결과는 조회 성공 그런데 문제가...!

데이터를 잘 가져오는데는 성공했지만 문제가 발생한다. 

 

콘솔을 확인해보면

총 3번의 쿼리가 나간다. 그렇다...그 유명한 N+1 문제가 발생한다.

한명의 회원이 남기는 타임라인 글은 총 2개이고 데이터베이스 관점에서 봤을 때는 2개니까 2번의 쿼리만 나오면 될 것 같은데 지연로딩 때문에 그렇지가 않다. 이렇게 몇 건 안되는 조회를 할 때는 크게 문제가 되지 않지만 대용량의 데이터를 조회한다면 쿼리를 호출하는 횟수가 기하 급수적으로 늘어날 것이다. 그렇다면 문제가 너무 많음.......그래서 또 추가적인 해결방법이 필요하다.

 

ver3. DTO로 변환 + 패치조인 사용

package seulgi.bookbookclub.repository;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.State;
import seulgi.bookbookclub.domain.Timeline;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Repository
public class TimelineRepository {

    @PersistenceContext
    private EntityManager em;

    // 코드생략 //

    public List<Timeline> findTimelinesByMember(Integer memberSeq) {
        return em.createQuery("SELECT t FROM Timeline t " +
                        "JOIN FETCH t.member " +
                        "JOIN FETCH t.book " +
                        "WHERE t.member.memberSeq = :memberSeq " +
                        "AND t.state = :state " +
                        "ORDER BY t.createdDate DESC", Timeline.class)
                .setParameter("memberSeq", memberSeq)
                .setParameter("state", State.ACTIVE)
                .getResultList();
    }

    // 코드생략 //


}

• 레파지토리에서 패치조인을 사용함.

 

 

당연히 조회는 잘되고

 

콘솔에도 2개의 타임라인만 한번에 조회 해준다.

 

패치조인은 한마디로 연관된 데이터를 한번해 조회히서 성능 최적화의 장점이 있지만

가져오는 데이터가 너무 많으면 오히려 성능이 느려질 수 있는 단점이 있고,

페이징 처리를 동시에 사용할 경우 패치조인은 여러 데이터를 한번에 가져오기 때문에

데이터 중복이 발생하거나 결과가 올바르지 않을 수도 있고,

보다 시피 쿼리가 아무래도 복잡해지는 단점들도 존재함. 

 

---

TimelineApiController.java

4. 팔로잉한 회원들의 타임라인 조회

*** DTO변환 + 패치 조인을 디폴트로 사용함

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.hibernate.sql.Delete;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.dto.TimelineDto;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

    //코드생략

    //팔로잉한 회원들의 타임라인 조회
    @GetMapping("/following/{memberSeq}")
    public Result timelinesByFollowing(@PathVariable("memberSeq") Integer memberSeq){
        List<Timeline> followedTimelines = timelineService.getFollowedTimelines(memberSeq);
        List<TimelineDto> collect = followedTimelines.stream()
                .map(t -> new TimelineDto(
                          t.getTimelineSeq()
                        , t.getMember().getMemberId()
                        , t.getMember().getNickname()
                        , t.getContents()
                        , t.getLikes()
                        , t.getBook().getTitle()
                        , t.getBook().getAuthor()
                        , t.getContents()
                        , t.getCreatedDate()))
                .collect(Collectors.toList());
        return new Result(collect);
    }


}

 

TimelineService.java

package seulgi.bookbookclub.repository;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.State;
import seulgi.bookbookclub.domain.Timeline;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Repository
public class TimelineRepository {

    @PersistenceContext
    private EntityManager em;

    //코드생략//
    
    // 팔로잉한 회원들의 타임라인 조회
    public List<Timeline> findByFollowers(List<Integer> memberSeqs) {
        return em.createQuery("SELECT t FROM Timeline t " +
                        "JOIN FETCH t.member " +
                        "JOIN FETCH t.book " +
                        "WHERE t.member.memberSeq IN :memberSeqs " +
                        "ORDER BY t.createdDate", Timeline.class)
                .setParameter("memberSeqs", memberSeqs)
                .getResultList();
    }


}

 

 

TimelineRepository.java

package seulgi.bookbookclub.repository;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.State;
import seulgi.bookbookclub.domain.Timeline;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Repository
public class TimelineRepository {

    @PersistenceContext
    private EntityManager em;

    //코드생략//

    //팔로잉한 회원들의 타임라인 조회
    public List<Timeline> findByFollowers(List<Integer> memberSeqs) {
        return em.createQuery("SELECT t FROM Timeline t " +
                        "JOIN FETCH t.member " +
                        "JOIN FETCH t.book " +
                        "WHERE t.member.memberSeq IN :memberSeqs " +
                        "ORDER BY t.createdDate", Timeline.class)
                .setParameter("memberSeqs", memberSeqs)
                .getResultList();
    }


}

 

[테스트 성공]

 

 

---

 

TimelineApiController.java

5. 타임라인ID로 타임라인 글 단건 조회

*** DTO변환 + 패치 조인을 디폴트로 사용함

package seulgi.bookbookclub.api;


import lombok.RequiredArgsConstructor;
import org.hibernate.sql.Delete;
import org.springframework.web.bind.annotation.*;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.dto.CreateTimelineRequest;
import seulgi.bookbookclub.dto.CreateTimelineResponse;
import seulgi.bookbookclub.dto.Result;
import seulgi.bookbookclub.dto.TimelineDto;
import seulgi.bookbookclub.service.TimelineService;

import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequiredArgsConstructor
@RequestMapping("/api/timelines")
public class TimelineApiController {

    private final TimelineService timelineService;

    //코드생략//

    //타임라인 ID로 타임라인 단건 조회
    @GetMapping("/{timelineSeq}")
    public Result timelineByTimelineId(@PathVariable("timelineSeq")Integer timelineSeq){
        Timeline timeline = timelineService.getTimelineByTimeLineId(timelineSeq);
        TimelineDto timelineDto = new TimelineDto(
                                  timeline.getTimelineSeq()
                                , timeline.getMember().getMemberId()
                                , timeline.getMember().getNickname()
                                , timeline.getContents()
                                , timeline.getLikes()
                                , timeline.getBook().getTitle()
                                , timeline.getBook().getAuthor()
                                , timeline.getBook().getPublisher()
                                , timeline.getCreatedDate()
                                );
        return new Result(timelineDto);
    }
}

 

 

TimelineService.java

package seulgi.bookbookclub.service;

import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import seulgi.bookbookclub.domain.Book;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.Member;
import seulgi.bookbookclub.domain.Timeline;
import seulgi.bookbookclub.repository.BookRepository;
import seulgi.bookbookclub.repository.MemberRepository;
import seulgi.bookbookclub.repository.TimelineRepository;

import java.util.List;
import java.util.stream.Collectors;

@Service
@Transactional(readOnly = true)
@RequiredArgsConstructor
public class TimelineService {

    private final TimelineRepository timelineRepository;
    private final MemberRepository memberRepository;
    private final BookRepository bookRepository;
    private final FollowService followService;

    //코드생략//
    
    // 타임라인 ID로 타임라인 단건 조회
    public Timeline getTimelineByTimeLineId(Integer timelineSeq){
         return timelineRepository.findById(timelineSeq);
    }

}

 

 

TimelineRepository.java

package seulgi.bookbookclub.repository;

import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.stereotype.Repository;
import seulgi.bookbookclub.domain.Follow;
import seulgi.bookbookclub.domain.State;
import seulgi.bookbookclub.domain.Timeline;

import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

@Repository
public class TimelineRepository {

    @PersistenceContext
    private EntityManager em;

    //코드생략//
    
    // 타임라인 ID로 타임라인 단건 조회
    public Timeline findById(Integer timelineSeq) {
        return em.createQuery("SELECT t FROM Timeline t WHERE t.timelineSeq = :timelineSeq AND t.state = :state", Timeline.class)
                .setParameter("timelineSeq", timelineSeq)
                .setParameter("state", State.ACTIVE)
                .getSingleResult();
    }

}

 

[테스트 성공]