Feat#9 좋아요기능

backend/src/main/java/org/juniortown/backend/controller/ExceptionController.java

@@ -56,7 +56,7 @@ public ResponseEntity<ErrorResponse> customException(CustomException e) {
 	public ResponseEntity<ErrorResponse> exceptionHandler(Exception e) {
 		log.error("Exception: ", e);
 		ErrorResponse response = ErrorResponse.builder()
-			.code("500")
+			.code(e.getMessage())
 			.message("서버 오류입니다.")
 			.build();
 

backend/src/main/java/org/juniortown/backend/like/controller/LikeController.java

@@ -0,0 +1,28 @@
+package org.juniortown.backend.like.controller;
+
+import org.juniortown.backend.like.dto.response.LikeResponse;
+import org.juniortown.backend.like.service.LikeService;
+import org.juniortown.backend.user.dto.CustomUserDetails;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import lombok.RequiredArgsConstructor;
+
+@RestController
+@RequestMapping("/api")
+@RequiredArgsConstructor
+public class LikeController {
+	private final LikeService likeService;
+	@PostMapping("/posts/likes/{postId}")
+	public ResponseEntity<LikeResponse> like(@AuthenticationPrincipal CustomUserDetails customUserDetails, @PathVariable Long postId) {
+		Long userId = customUserDetails.getUserId();
+		LikeResponse response = likeService.likePost(userId, postId);
+		return ResponseEntity.status(HttpStatus.CREATED).body(response);
+	}
+}

backend/src/main/java/org/juniortown/backend/like/dto/response/LikeResponse.java

@@ -0,0 +1,19 @@
+package org.juniortown.backend.like.dto.response;
+
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Getter
+@NoArgsConstructor
+public class LikeResponse {
+	private Long userId;
+	private Long postId;
+	private Boolean isLiked;
+	@Builder
+	public LikeResponse(Long userId, Long postId, Boolean isLiked) {
+		this.userId = userId;
+		this.postId = postId;
+		this.isLiked = isLiked;
+	}
+}

backend/src/main/java/org/juniortown/backend/like/entity/Like.java

@@ -0,0 +1,42 @@
+package org.juniortown.backend.like.entity;
+
+import org.juniortown.backend.post.entity.Post;
+import org.juniortown.backend.user.entity.User;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.OneToOne;
+import jakarta.persistence.Table;
+import lombok.AccessLevel;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Table(name = "likes")
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@Getter
+public class Like {
+	@Id
+	@GeneratedValue(strategy = GenerationType.IDENTITY)
+	private Long id;
+
+	@ManyToOne
+	@JoinColumn(name = "user_id", nullable = false)
+	private User user;
+
+	@ManyToOne
+	@JoinColumn(name = "post_id", nullable = false)
+	private Post post;
+
+	@Builder
+	public Like(User user, Post post) {
+		this.user = user;
+		this.post = post;
+	}
+
+}

backend/src/main/java/org/juniortown/backend/like/exception/LikeFailureException.java

@@ -0,0 +1,17 @@
+package org.juniortown.backend.like.exception;
+
+import org.juniortown.backend.exception.CustomException;
+
+import lombok.Getter;
+
+
+public class LikeFailureException extends CustomException {
+	public static final String MESSAGE = "게시글이 삭제되었거나, 좋아요 처리 실패";
+	public LikeFailureException(Exception e) {
+		super(MESSAGE, e);
+	}
+	@Override
+	public int getStatusCode() {
+		return 500;
+	}
+}

backend/src/main/java/org/juniortown/backend/like/repository/LikeRepository.java

@@ -0,0 +1,12 @@
+package org.juniortown.backend.like.repository;
+
+import java.util.Optional;
+
+import org.juniortown.backend.like.entity.Like;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface LikeRepository extends JpaRepository<Like, Long> {
+	Optional<Like> findByUserIdAndPostId(Long userId, Long postId);
+}

backend/src/main/java/org/juniortown/backend/like/service/LikeService.java

@@ -0,0 +1,60 @@
+package org.juniortown.backend.like.service;
+
+import java.util.Optional;
+
+import org.juniortown.backend.like.dto.response.LikeResponse;
+import org.juniortown.backend.like.entity.Like;
+import org.juniortown.backend.like.exception.LikeFailureException;
+import org.juniortown.backend.like.repository.LikeRepository;
+import org.juniortown.backend.post.entity.Post;
+import org.juniortown.backend.post.repository.PostRepository;
+import org.juniortown.backend.user.entity.User;
+import org.juniortown.backend.user.repository.UserRepository;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import lombok.RequiredArgsConstructor;
+
+@Service
+@RequiredArgsConstructor
+public class LikeService {
+	private final LikeRepository likeRepository;
+	private final UserRepository userRepository;
+	private final PostRepository postRepository;
+	@Transactional
+	public LikeResponse likePost(Long userId, Long postId) {
+		User user = userRepository.getReferenceById(userId);
+		Post post = postRepository.getReferenceById(postId);
+		Optional<Like> like = likeRepository.findByUserIdAndPostId(userId, postId);
+
+		if(like.isEmpty()){
+			try{
+				likeRepository.save(Like.builder()
+					.user(user)
+					// 저장하는 시점에 post가 삭제될 수 있으니까 try-catch로 잡음.
+					.post(post)
+					.build()
+				);
+				return LikeResponse.builder()
+					.userId(userId)
+					.postId(postId)
+					.isLiked(true)
+					.build();
+			}catch (Exception e) {
+				throw new LikeFailureException(e);
+			}
+		}
+		else{
+			likeRepository.deleteById(like.get().getId());
+
+			return LikeResponse.builder()
+				.userId(userId)
+				.postId(postId)
+				.isLiked(false)
+				.build();
+		}
+
+
+	}
+
+}

backend/src/main/java/org/juniortown/backend/post/controller/PostController.java

@@ -2,8 +2,9 @@
 
 import org.juniortown.backend.post.dto.request.PostCreateRequest;
 import org.juniortown.backend.post.dto.response.PageResponse;
-import org.juniortown.backend.post.dto.response.PostSearchResponse;
+import org.juniortown.backend.post.dto.response.PostWithLikeCount;
 import org.juniortown.backend.post.dto.response.PostResponse;
+import org.juniortown.backend.post.dto.response.PostWithLikeCountProjection;
 import org.juniortown.backend.post.service.PostService;
 import org.juniortown.backend.user.dto.CustomUserDetails;
 import org.springframework.data.domain.Page;
@@ -54,9 +55,12 @@ public ResponseEntity<PostResponse> update(@AuthenticationPrincipal CustomUserDe
 
 	// 게시글 목록 조회, 페이지네이션 적용
 	@GetMapping("/posts/{page}")
-	public ResponseEntity<PageResponse<PostSearchResponse>> getPosts(@PathVariable int page) {
-	 	Page<PostSearchResponse> posts = postService.getPosts(page);
-		PageResponse<PostSearchResponse> response = new PageResponse<>(posts);
+	public ResponseEntity<PageResponse<PostWithLikeCountProjection>> getPosts(@AuthenticationPrincipal CustomUserDetails customUserDetails, @PathVariable int page) {
+		Long userId = customUserDetails.getUserId();
+		// null체크
+
+	 	Page<PostWithLikeCountProjection> posts = postService.getPosts(userId, page);
+		PageResponse<PostWithLikeCountProjection> response = new PageResponse<>(posts);
 		return ResponseEntity.ok(response);
 	}
 

backend/src/main/java/org/juniortown/backend/post/dto/response/PostSearchResponse.java → backend/src/main/java/org/juniortown/backend/post/dto/response/PostWithLikeCount.java

@@ -7,23 +7,35 @@
 import lombok.Getter;
 
 @Getter
-public class PostSearchResponse {
+public class PostWithLikeCount {
 	private Long id;
 	private String title;
 	private String username;
 	private Long userId;
+	private Long likeCount;
 	private LocalDateTime createdAt;
 	private LocalDateTime updatedAt;
 	private LocalDateTime deletedAt;
 
-	public PostSearchResponse(Post post) {
+	public PostWithLikeCount(Post post) {
 		this.id = post.getId();
 		this.title = post.getTitle();
-		// 이거 null 체크 어지럽네
 		this.username = post.getUser().getName();
 		this.userId = post.getUser().getId();
 		this.createdAt = post.getCreatedAt();
 		this.updatedAt = post.getUpdatedAt();
 		this.deletedAt = post.getDeletedAt();
 	}
+
+	// 생성자 기반 DTO 매핑
+	public PostWithLikeCount(Long id, String title, String username, Long userId, Long likeCount, LocalDateTime createdAt, LocalDateTime updatedAt, LocalDateTime deletedAt) {
+		this.id = id;
+		this.title = title;
+		this.username = username;
+		this.userId = userId;
+		this.likeCount = likeCount;
+		this.createdAt = createdAt;
+		this.updatedAt = updatedAt;
+		this.deletedAt = deletedAt;
+	}
 }

backend/src/main/java/org/juniortown/backend/post/dto/response/PostWithLikeCountProjection.java

@@ -0,0 +1,14 @@
+package org.juniortown.backend.post.dto.response;
+
+import java.time.LocalDateTime;
+
+public interface PostWithLikeCountProjection {
+	Long getId();
+	String getTitle();
+	String getUsername();
+	Long getUserId();
+	Long getLikeCount();
+	Boolean getIsLiked();
+	LocalDateTime getCreatedAt();
+	LocalDateTime getUpdatedAt();
+}

backend/src/main/java/org/juniortown/backend/post/repository/PostRepository.java

@@ -1,14 +1,31 @@
 package org.juniortown.backend.post.repository;
 
-
-
+import org.juniortown.backend.post.dto.response.PostWithLikeCountProjection;
 import org.juniortown.backend.post.entity.Post;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface PostRepository extends JpaRepository<Post, Long>, PostRepositoryCustom {
 	Page<Post> findAllByDeletedAtIsNull(Pageable pageable);
+
+	@Query(
+		"SELECT p.id AS id, p.title AS title, u.name AS username, u.id AS userId, COUNT(l.id) AS likeCount, " +
+			"p.createdAt AS createdAt, p.updatedAt AS updatedAt, " +
+			"CASE WHEN EXISTS (" +
+			"   SELECT 1 FROM Like l2 WHERE l2.post.id = p.id AND l2.user.id = :userId" +
+			") THEN true ELSE false END AS isLiked " +
+			"FROM Post p " +
+			"JOIN p.user u " +
+			"LEFT JOIN Like l ON l.post.id = p.id " +
+			"WHERE p.deletedAt IS NULL " +
+			"GROUP BY p.id, p.title, u.name, u.id, p.createdAt, p.updatedAt, p.deletedAt"
+	)
+	Page<PostWithLikeCountProjection> findAllWithLikeCount(@Param("userId") Long userId, Pageable pageable);
+
+
 }

backend/src/main/java/org/juniortown/backend/post/service/PostService.java

@@ -2,7 +2,8 @@
 
 import java.time.Clock;
 
-import org.juniortown.backend.post.dto.response.PostSearchResponse;
+import org.juniortown.backend.post.dto.response.PostWithLikeCount;
+import org.juniortown.backend.post.dto.response.PostWithLikeCountProjection;
 import org.juniortown.backend.post.exception.PostNotFoundException;
 import org.juniortown.backend.post.dto.request.PostCreateRequest;
 import org.juniortown.backend.post.dto.response.PostResponse;
@@ -71,11 +72,11 @@ public PostResponse update(Long postId, Long userId, PostCreateRequest postCreat
 		return new PostResponse(post);
 	}
 	@Transactional(readOnly = true)
-	public Page<PostSearchResponse> getPosts(int page) {
+	public Page<PostWithLikeCountProjection> getPosts(Long userId, int page) {
 		Pageable pageable = PageRequest.of(page, PAGE_SIZE, Sort.by("createdAt").descending());
-		Page<Post> postPage = postRepository.findAllByDeletedAtIsNull(pageable);
-
-		return postPage.map(post -> new PostSearchResponse(post));
+		Page<PostWithLikeCountProjection> postPage = postRepository.findAllWithLikeCount(userId, pageable);
+		return postPage;
+		//return postPage.map(post -> new PostWithLikeCount(post));
 	}
 	@Transactional(readOnly = true)
 	public PostResponse getPost(Long postId) {