refactor/#130 게시글 상세 조회 시 이전, 다음 게시글 정보 추가

aics-api/src/main/java/kgu/developers/api/post/application/PostService.java

@@ -1,24 +1,26 @@
 package kgu.developers.api.post.application;
 
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+import org.springframework.data.domain.PageRequest;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
 import kgu.developers.api.post.presentation.exception.PostNotFoundException;
 import kgu.developers.api.post.presentation.request.PostRequest;
 import kgu.developers.api.post.presentation.response.PostDetailResponse;
 import kgu.developers.api.post.presentation.response.PostPersistResponse;
 import kgu.developers.api.post.presentation.response.PostSummaryPageResponse;
+import kgu.developers.api.post.presentation.response.PostTitleResponse;
 import kgu.developers.api.user.application.UserService;
 import kgu.developers.common.response.PaginatedListResponse;
 import kgu.developers.domain.post.domain.Category;
 import kgu.developers.domain.post.domain.Post;
 import kgu.developers.domain.post.domain.PostRepository;
 import kgu.developers.domain.user.domain.User;
 import lombok.RequiredArgsConstructor;
-import org.springframework.data.domain.PageRequest;
-import org.springframework.scheduling.annotation.Scheduled;
-import org.springframework.stereotype.Service;
-import org.springframework.transaction.annotation.Transactional;
-
-import java.time.LocalDateTime;
-import java.time.format.DateTimeFormatter;
 
 @Service
 @RequiredArgsConstructor
@@ -39,17 +41,26 @@ public PostPersistResponse createPost(PostRequest request, Category category) {
 	}
 
 	public PostSummaryPageResponse getPostsByKeywordAndCategory(PageRequest request, String keyword,
-																Category category) {
+		Category category) {
 		PaginatedListResponse<Post> paginatedListResponse = postRepository.findAllByTitleContainingAndCategoryOrderByCreatedAtDesc(
 			keyword, category, request);
 		return PostSummaryPageResponse.of(paginatedListResponse.contents(), paginatedListResponse.pageable());
 	}
 
-	@Transactional(readOnly = true)
-	public PostDetailResponse getPostById(Long postId) {
+	@Transactional
+	public PostDetailResponse getPostByIdWithPrevAndNext(Long postId) {
 		Post post = getById(postId);
 		post.increaseViews();
-		return PostDetailResponse.from(post);
+
+		LocalDateTime timestamp = post.getCreatedAt();
+		Category category = post.getCategory();
+
+		Post prevPost = postRepository.findByPrevPost(timestamp, category).orElse(null);
+		Post nextPost = postRepository.findByNextPost(timestamp, category).orElse(null);
+
+		PostTitleResponse prevPostResponse = PostTitleResponse.from(prevPost);
+		PostTitleResponse nextPostResponse = PostTitleResponse.from(nextPost);
+		return PostDetailResponse.from(post, prevPostResponse, nextPostResponse);
 	}
 
 	@Transactional

aics-api/src/main/java/kgu/developers/api/post/presentation/PostController.java

@@ -77,7 +77,7 @@ public ResponseEntity<PostSummaryPageResponse> getPostsByKeywordAndCategory(
 	public ResponseEntity<PostDetailResponse> getPostById(
 		@Parameter(description = "조회할 게시글의 id", example = "1", required = true) @PathVariable @Positive Long postId
 	) {
-		PostDetailResponse response = postService.getPostById(postId);
+		PostDetailResponse response = postService.getPostByIdWithPrevAndNext(postId);
 		return ResponseEntity.ok(response);
 	}
 

aics-api/src/main/java/kgu/developers/api/post/presentation/response/PostDetailResponse.java

@@ -50,10 +50,22 @@ public record PostDetailResponse(
 
 	@Schema(description = "작성일", example = "2024-11-11 15:45", requiredMode = REQUIRED)
 	@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm")
-	String createdAt
+	String createdAt,
+
+	@Schema(description = "이전 게시글 정보",
+		example = "{\"id\": 1,"
+			+ " \"title\": \"이전 게시글 제목\"}",
+		requiredMode = REQUIRED, nullable = true)
+	PostTitleResponse prevPost,
+
+	@Schema(description = "다음 게시글 정보",
+		example = "{\"id\": 1, "
+			+ "\"title\": \"이전 게시글 제목\"}",
+		requiredMode = REQUIRED, nullable = true)
+	PostTitleResponse nextPost
 
 ) {
-	public static PostDetailResponse from(Post post) {
+	public static PostDetailResponse from(Post post, PostTitleResponse prevPost, PostTitleResponse nextPost) {
 		DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
 		return PostDetailResponse.builder()
 			.postId(post.getId())
@@ -65,6 +77,8 @@ public static PostDetailResponse from(Post post) {
 			.isPinned(post.isPinned())
 			.file(post.getFile() != null ? FileResponse.from(post.getFile()) : null)
 			.createdAt(post.getCreatedAt().format(formatter))
+			.prevPost(prevPost)
+			.nextPost(nextPost)
 			.build();
 	}
 }

aics-api/src/main/java/kgu/developers/api/post/presentation/response/PostTitleResponse.java

@@ -0,0 +1,25 @@
+package kgu.developers.api.post.presentation.response;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import kgu.developers.domain.post.domain.Post;
+import lombok.Builder;
+
+@Builder
+public record PostTitleResponse(
+	@Schema(description = "게시글 id", example = "1", nullable = true)
+	Long postId,
+
+	@Schema(description = "게시글 제목", example = "SW 부트캠프 4기 교육생 모집", nullable = true)
+	String postTitle
+) {
+	public static PostTitleResponse from(Post post) {
+		if (post == null) {
+			return null;
+		}
+
+		return PostTitleResponse.builder()
+			.postId(post.getId())
+			.postTitle(post.getTitle())
+			.build();
+	}
+}

aics-api/src/testFixtures/java/post/application/PostServiceTest.java

@@ -3,6 +3,17 @@
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.security.core.context.SecurityContext;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
 
 import kgu.developers.api.post.application.PostService;
 import kgu.developers.api.post.presentation.exception.PostNotFoundException;
@@ -17,15 +28,6 @@
 import kgu.developers.domain.user.domain.User;
 import mock.FakePostRepository;
 import mock.FakeUserRepository;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.DisplayName;
-import org.junit.jupiter.api.Test;
-import org.springframework.data.domain.PageRequest;
-import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
-import org.springframework.security.core.context.SecurityContext;
-import org.springframework.security.core.context.SecurityContextHolder;
-import org.springframework.security.core.userdetails.UserDetails;
-import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
 
 public class PostServiceTest {
 	private PostService postService;
@@ -82,25 +84,44 @@ public void createPost_Success() {
 		assertEquals(3, response.postId());
 
 		// when
-		PostDetailResponse created = postService.getPostById(response.postId());
+		Post created = postService.getById(response.postId());
 
 		// then
-		assertEquals(request.title(), created.title());
-		assertEquals(request.content(), created.content());
-		assertEquals(category.getDescription(), created.category());
+		assertEquals(request.title(), created.getTitle());
+		assertEquals(request.content(), created.getContent());
+		assertEquals(category.getDescription(), created.getCategory().getDescription());
 	}
 
 	@Test
-	@DisplayName("getPostById는 게시글을 조회할 수 있다")
+	@DisplayName("getPostById는 해당 게시글과 이전, 다음 게시글을 조회할 수 있다")
 	public void getPostById_Success() {
 		// given
 		Long postId = 1L;
 
 		// when
-		PostDetailResponse response = postService.getPostById(postId);
+		PostDetailResponse response = postService.getPostByIdWithPrevAndNext(postId);
 
 		// then
 		assertEquals(postId, response.postId());
+		assertNull(response.prevPost());
+		assertEquals(response.nextPost().postId(), 2L);
+		assertEquals(response.nextPost().postTitle(), "테스트용 제목2");
+	}
+
+	@Test
+	@DisplayName("getPostById는 마지막 게시글 조회 시 다음 게시글은 null이어야 한다")
+	public void getPostById_LastPost_Success() {
+		// given
+		Long lastPostId = 2L;
+
+		// when
+		PostDetailResponse response = postService.getPostByIdWithPrevAndNext(lastPostId);
+
+		// then
+		assertEquals(lastPostId, response.postId());
+		assertNull(response.nextPost());
+		assertEquals(response.prevPost().postId(), 1L);
+		assertEquals(response.prevPost().postTitle(), "테스트용 제목1");
 	}
 
 	@Test
@@ -112,7 +133,7 @@ public void getPostById_Throws_PostNotFoundException() {
 		// when
 		// then
 		assertThatThrownBy(
-			() -> postService.getPostById(postId)
+			() -> postService.getPostByIdWithPrevAndNext(postId)
 		).isInstanceOf(PostNotFoundException.class);
 	}
 
@@ -139,13 +160,13 @@ public void getPostsByKeywordAndCategory_Success() {
 	public void togglePostPinStatus_Success() {
 		// given
 		Long postId = 1L;
-		PostDetailResponse before = postService.getPostById(postId);
+		PostDetailResponse before = postService.getPostByIdWithPrevAndNext(postId);
 
 		// when
 		postService.togglePostPinStatus(postId);
 
 		// then
-		PostDetailResponse after = postService.getPostById(postId);
+		PostDetailResponse after = postService.getPostByIdWithPrevAndNext(postId);
 		assertNotEquals(before.isPinned(), after.isPinned());
 	}
 
@@ -160,7 +181,7 @@ public void deletePost_Throws_PostNotFoundException() {
 
 		// then
 		assertThatThrownBy(
-			() -> postService.getPostById(postId)
+			() -> postService.getPostByIdWithPrevAndNext(postId)
 		).isInstanceOf(PostNotFoundException.class);
 	}
 }

aics-domain/src/main/java/kgu/developers/domain/post/domain/PostRepository.java

@@ -1,5 +1,6 @@
 package kgu.developers.domain.post.domain;
 
+import java.time.LocalDateTime;
 import java.util.Optional;
 
 import org.springframework.data.domain.Pageable;
@@ -15,4 +16,8 @@ PaginatedListResponse<Post> findAllByTitleContainingAndCategoryOrderByCreatedAtD
 	Optional<Post> findById(Long postId);
 
 	void deleteAllByDeletedAtBefore(int retentionDays);
+
+	Optional<Post> findByPrevPost(LocalDateTime createdAt, Category category);
+
+	Optional<Post> findByNextPost(LocalDateTime createdAt, Category category);
 }

aics-domain/src/main/java/kgu/developers/domain/post/infrastructure/JpaPostRepository.java

@@ -1,7 +1,17 @@
 package kgu.developers.domain.post.infrastructure;
 
-import kgu.developers.domain.post.domain.Post;
+import java.time.LocalDateTime;
+import java.util.Optional;
+
 import org.springframework.data.jpa.repository.JpaRepository;
 
+import kgu.developers.domain.post.domain.Category;
+import kgu.developers.domain.post.domain.Post;
+
 public interface JpaPostRepository extends JpaRepository<Post, Long> {
+	Optional<Post> findFirstByCreatedAtLessThanAndDeletedAtIsNullAndCategoryOrderByCreatedAtDesc(
+		LocalDateTime createdAt, Category category);
+
+	Optional<Post> findFirstByCreatedAtGreaterThanAndDeletedAtIsNullAndCategoryOrderByCreatedAtAsc(
+		LocalDateTime createdAt, Category category);
 }

aics-domain/src/main/java/kgu/developers/domain/post/infrastructure/PostRepositoryImpl.java

@@ -1,5 +1,6 @@
 package kgu.developers.domain.post.infrastructure;
 
+import java.time.LocalDateTime;
 import java.util.Optional;
 
 import org.springframework.data.domain.Pageable;
@@ -38,4 +39,16 @@ public void deleteAllByDeletedAtBefore(int retentionDays) {
 		queryPostRepository.deleteAllByDeletedAtBefore(retentionDays);
 	}
 
+	@Override
+	public Optional<Post> findByPrevPost(LocalDateTime createdAt, Category category) {
+		return jpaPostRepository.findFirstByCreatedAtLessThanAndDeletedAtIsNullAndCategoryOrderByCreatedAtDesc(
+			createdAt, category);
+	}
+
+	@Override
+	public Optional<Post> findByNextPost(LocalDateTime createdAt, Category category) {
+		return jpaPostRepository.findFirstByCreatedAtGreaterThanAndDeletedAtIsNullAndCategoryOrderByCreatedAtAsc(
+			createdAt, category);
+	}
+
 }

aics-domain/src/testFixtures/java/mock/FakePostRepository.java

@@ -1,12 +1,5 @@
 package mock;
 
-import kgu.developers.common.response.PageableResponse;
-import kgu.developers.common.response.PaginatedListResponse;
-import kgu.developers.domain.post.domain.Category;
-import kgu.developers.domain.post.domain.Post;
-import kgu.developers.domain.post.domain.PostRepository;
-import org.springframework.data.domain.Pageable;
-
 import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -16,6 +9,14 @@
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Collectors;
 
+import org.springframework.data.domain.Pageable;
+
+import kgu.developers.common.response.PageableResponse;
+import kgu.developers.common.response.PaginatedListResponse;
+import kgu.developers.domain.post.domain.Category;
+import kgu.developers.domain.post.domain.Post;
+import kgu.developers.domain.post.domain.PostRepository;
+
 public class FakePostRepository implements PostRepository {
 	private final List<Post> data = Collections.synchronizedList(new ArrayList<>());
 	private final AtomicLong autoGeneratedId = new AtomicLong(0);
@@ -58,7 +59,7 @@ public PaginatedListResponse<Post> findAllByTitleContainingAndCategoryOrderByCre
 			.sorted(Comparator.comparing(Post::getCreatedAt).reversed())
 			.collect(Collectors.toList());
 
-		int start = (int) pageable.getOffset();
+		int start = (int)pageable.getOffset();
 		int end = Math.min(start + pageable.getPageSize(), filteredPosts.size());
 
 		List<Post> paginatedPosts = start > filteredPosts.size() ?
@@ -84,4 +85,20 @@ public void deleteAllByDeletedAtBefore(int retentionDays) {
 		LocalDateTime threshold = LocalDateTime.now().minusDays(retentionDays);
 		data.removeIf(post -> post.getDeletedAt() != null && post.getDeletedAt().isBefore(threshold));
 	}
+
+	@Override
+	public Optional<Post> findByPrevPost(LocalDateTime createdAt, Category category) {
+		return data.stream()
+			.filter(post -> post.getCreatedAt().isBefore(createdAt) && post.getCategory().equals(category)
+				&& post.getDeletedAt() == null)
+			.max(Comparator.comparing(Post::getCreatedAt));
+	}
+
+	@Override
+	public Optional<Post> findByNextPost(LocalDateTime createdAt, Category category) {
+		return data.stream()
+			.filter(post -> post.getCreatedAt().isAfter(createdAt) && post.getCategory().equals(category)
+				&& post.getDeletedAt() == null)
+			.min(Comparator.comparing(Post::getCreatedAt));
+	}
 }