project-mos · lsh2613 · May 6, 2025 · Apr 28, 2025 · Apr 28, 2025 · Apr 28, 2025
diff --git a/src/main/java/com/mos/backend/common/dto/InfinityScrollRes.java b/src/main/java/com/mos/backend/common/dto/InfinityScrollRes.java
@@ -0,0 +1,29 @@
+package com.mos.backend.common.dto;
+
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.ToString;
+
+import java.util.List;
+
+@ToString
+@NoArgsConstructor
+public class InfinityScrollRes<T> {
+    @Getter
+    private List<T> content;
+    @Getter
+    private Long lastElementId;
+    private boolean hasNext;
+
+    public static <T> InfinityScrollRes<T> of(List<T> content, Long lastElementId, boolean hasNext) {
+        InfinityScrollRes<T> infinityScrollRes = new InfinityScrollRes<>();
+        infinityScrollRes.content = content;
+        infinityScrollRes.hasNext = hasNext;
+        infinityScrollRes.lastElementId = lastElementId;
+        return infinityScrollRes;
+    }
+
+    public boolean hasNext() {
+        return hasNext;
+    }
+}
diff --git a/src/main/java/com/mos/backend/common/utils/InfinityScrollUtil.java b/src/main/java/com/mos/backend/common/utils/InfinityScrollUtil.java
@@ -0,0 +1,19 @@
+package com.mos.backend.common.utils;
+
+import java.util.List;
+import java.util.Optional;
+
+public class InfinityScrollUtil {
+    public static <T> Optional<T> getLastElement(List<T> content) {
+        if (content.isEmpty()) return Optional.empty();
+
+        T t = content.get(content.size() - 1);
+
+        return Optional.ofNullable(t);
+    }
+
+    public static <T> boolean hasNext(List<T> list, int pageSize) {
+        return list.size() > pageSize;
+    }
+
+}
diff --git a/src/main/java/com/mos/backend/privatechatmessages/application/PrivateChatMessageService.java b/src/main/java/com/mos/backend/privatechatmessages/application/PrivateChatMessageService.java
@@ -1,9 +1,12 @@
 package com.mos.backend.privatechatmessages.application;
 
+import com.mos.backend.common.dto.InfinityScrollRes;
 import com.mos.backend.common.exception.MosException;
 import com.mos.backend.common.infrastructure.EntityFacade;
 import com.mos.backend.common.redis.RedisPublisher;
+import com.mos.backend.common.utils.InfinityScrollUtil;
 import com.mos.backend.privatechatmessages.application.dto.PrivateChatMessageDto;
+import com.mos.backend.privatechatmessages.application.res.PrivateChatMessageRes;
 import com.mos.backend.privatechatmessages.entity.PrivateChatMessage;
 import com.mos.backend.privatechatmessages.infrastructure.PrivateChatMessageRepository;
 import com.mos.backend.privatechatmessages.presentation.req.PrivateChatMessagePublishReq;
@@ -14,6 +17,9 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.List;
+import java.util.Optional;
+
 @RequiredArgsConstructor
 @Service
 public class PrivateChatMessageService {
@@ -47,4 +53,30 @@ private PrivateChatMessage savePrivateChatMessage(User user, PrivateChatRoom pri
         PrivateChatMessage privateChatMessage = PrivateChatMessage.of(user, privateChatRoom, message);
         return privateChatMessageRepository.save(privateChatMessage);
     }
+
+    @Transactional(readOnly = true)
+    public InfinityScrollRes<PrivateChatMessageRes> getPrivateChatMessages(Long userId, Long privateChatRoomId, Long lastPrivateChatMessageId, int size) {
+        User user = entityFacade.getUser(userId);
+        PrivateChatRoom privateChatRoom = entityFacade.getPrivateChatRoom(privateChatRoomId);
+
+        if (isNotChatRoomMember(user, privateChatRoom))
+            throw new MosException(PrivateChatRoomErrorCode.FORBIDDEN);
+
+        List<PrivateChatMessage> privateChatMessages = privateChatMessageRepository.findAllByChatRoomIdForInfiniteScroll(
+                privateChatRoom.getId(), lastPrivateChatMessageId, size
+        );
+
+        boolean hasNext = InfinityScrollUtil.hasNext(privateChatMessages, size);
+        if (hasNext)
+            privateChatMessages.remove(privateChatMessages.size() - 1);
+
+        Optional<PrivateChatMessage> lastElement = InfinityScrollUtil.getLastElement(privateChatMessages);
+        Long lastElementId = lastElement.map(PrivateChatMessage::getId).orElse(null);
+
+        List<PrivateChatMessageRes> privateChatMessageResList = privateChatMessages.stream()
+                .map(PrivateChatMessageRes::of)
+                .toList();
+
+        return InfinityScrollRes.of(privateChatMessageResList, lastElementId, hasNext);
+    }
 }
diff --git a/src/main/java/com/mos/backend/privatechatmessages/application/res/PrivateChatMessageRes.java b/src/main/java/com/mos/backend/privatechatmessages/application/res/PrivateChatMessageRes.java
@@ -0,0 +1,28 @@
+package com.mos.backend.privatechatmessages.application.res;
+
+import com.mos.backend.privatechatmessages.entity.PrivateChatMessage;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+
+@Getter
+@NoArgsConstructor
+public class PrivateChatMessageRes {
+    private Long privateChatMessageId;
+    private String message;
+    private LocalDateTime messageCreatedAt;
+
+    private Long userId;
+    private String nickname;
+
+    public static PrivateChatMessageRes of(PrivateChatMessage privateChatMessage) {
+        PrivateChatMessageRes privateChatMessageRes = new PrivateChatMessageRes();
+        privateChatMessageRes.privateChatMessageId = privateChatMessage.getId();
+        privateChatMessageRes.message = privateChatMessage.getMessage();
+        privateChatMessageRes.messageCreatedAt = privateChatMessage.getCreatedAt();
+        privateChatMessageRes.userId = privateChatMessage.getUser().getId();
+        privateChatMessageRes.nickname = privateChatMessage.getUser().getNickname();
+        return privateChatMessageRes;
+    }
+}
diff --git a/.../mos/backend/privatechatmessages/infrastructure/PrivateChatMessageQueryDslRepository.java b/.../mos/backend/privatechatmessages/infrastructure/PrivateChatMessageQueryDslRepository.java
@@ -0,0 +1,38 @@
+package com.mos.backend.privatechatmessages.infrastructure;
+
+import com.mos.backend.privatechatmessages.entity.PrivateChatMessage;
+import com.querydsl.core.types.Predicate;
+import com.querydsl.core.types.dsl.BooleanExpression;
+import com.querydsl.jpa.impl.JPAQueryFactory;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+
+import static com.mos.backend.privatechatmessages.entity.QPrivateChatMessage.privateChatMessage;
+
+@RequiredArgsConstructor
+@Repository
+public class PrivateChatMessageQueryDslRepository {
+    private final JPAQueryFactory queryFactory;
+
+    public List<PrivateChatMessage> findByChatRoomIdForInfiniteScroll(Long privateChatRoomId, Long lastPrivateChatMessageId, int size) {
+        return queryFactory
+                .selectFrom(privateChatMessage)
+                .where(
+                        eqPrivateChatRoomId(privateChatRoomId),
+                        ltPrivateChatMessageId(lastPrivateChatMessageId)
+                )
+                .orderBy(privateChatMessage.id.desc())
+                .limit(size + 1)
+                .fetch();
+    }
+
+    private static BooleanExpression eqPrivateChatRoomId(Long privateChatRoomId) {
+        return privateChatMessage.privateChatRoom.id.eq(privateChatRoomId);
+    }
+
+    private BooleanExpression ltPrivateChatMessageId(Long lastPrivateChatMessageId) {
+        return lastPrivateChatMessageId == null ? null : privateChatMessage.id.lt(lastPrivateChatMessageId);
+    }
+}
diff --git a/...java/com/mos/backend/privatechatmessages/infrastructure/PrivateChatMessageRepository.java b/...java/com/mos/backend/privatechatmessages/infrastructure/PrivateChatMessageRepository.java
@@ -3,10 +3,13 @@
 import com.mos.backend.privatechatmessages.entity.PrivateChatMessage;
 import com.mos.backend.privatechatrooms.entity.PrivateChatRoom;
 
+import java.util.List;
 import java.util.Optional;
 
 public interface PrivateChatMessageRepository {
     PrivateChatMessage save(PrivateChatMessage privateChatMessage);
 
     Optional<PrivateChatMessage> findFirstByPrivateChatRoomOrderByCreatedByDesc(PrivateChatRoom privateChatRoom);
+
+    List<PrivateChatMessage> findAllByChatRoomIdForInfiniteScroll(Long privateChatRoomId, Long lastPrivateChatMessageId, int size);
 }
diff --git a/.../com/mos/backend/privatechatmessages/infrastructure/PrivateChatMessageRepositoryImpl.java b/.../com/mos/backend/privatechatmessages/infrastructure/PrivateChatMessageRepositoryImpl.java
@@ -5,12 +5,14 @@
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
 import java.util.Optional;
 
 @Repository
 @RequiredArgsConstructor
 public class PrivateChatMessageRepositoryImpl implements PrivateChatMessageRepository {
     private final PrivateChatMessageJpaRepository privateChatMessageJpaRepository;
+    private final PrivateChatMessageQueryDslRepository privateChatMessageQueryDslRepository;
 
     @Override
     public PrivateChatMessage save(PrivateChatMessage privateChatMessage) {
@@ -21,4 +23,9 @@ public PrivateChatMessage save(PrivateChatMessage privateChatMessage) {
     public Optional<PrivateChatMessage> findFirstByPrivateChatRoomOrderByCreatedByDesc(PrivateChatRoom privateChatRoom) {
         return privateChatMessageJpaRepository.findFirstByPrivateChatRoomOrderByCreatedByDesc(privateChatRoom);
     }
+
+    @Override
+    public List<PrivateChatMessage> findAllByChatRoomIdForInfiniteScroll(Long privateChatRoomId, Long lastPrivateChatMessageId, int size) {
+        return privateChatMessageQueryDslRepository.findByChatRoomIdForInfiniteScroll(privateChatRoomId, lastPrivateChatMessageId, size);
+    }
 }
diff --git a/...backend/privatechatmessages/presentation/controller/api/PrivateChatMessageController.java b/...backend/privatechatmessages/presentation/controller/api/PrivateChatMessageController.java
@@ -1,11 +1,17 @@
 package com.mos.backend.privatechatmessages.presentation.controller.api;
 
 import com.mos.backend.common.annotation.Sender;
+import com.mos.backend.common.dto.InfinityScrollRes;
 import com.mos.backend.privatechatmessages.application.PrivateChatMessageService;
+import com.mos.backend.privatechatmessages.application.res.PrivateChatMessageRes;
 import com.mos.backend.privatechatmessages.presentation.req.PrivateChatMessagePublishReq;
 import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
 import org.springframework.messaging.handler.annotation.MessageMapping;
-import org.springframework.web.bind.annotation.RestController;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
 
 @RequiredArgsConstructor
 @RestController
@@ -16,4 +22,13 @@ public class PrivateChatMessageController {
     public void publishPrivateChatMessage(@Sender Long userId, PrivateChatMessagePublishReq privateChatMessagePublishReq) {
         privateChatMessageService.publish(userId, privateChatMessagePublishReq);
     }
+
+    @ResponseStatus(HttpStatus.OK)
+    @GetMapping("/private-chat-rooms/{privateChatRoomId}/messages")
+    public InfinityScrollRes<PrivateChatMessageRes> getPrivateChatMessages(@AuthenticationPrincipal Long userId,
+                                                                           @PathVariable Long privateChatRoomId,
+                                                                           @RequestParam(required = false) Long lastPrivateChatMessageId,
+                                                                           @RequestParam(defaultValue = "10") int size) {
+        return privateChatMessageService.getPrivateChatMessages(userId, privateChatRoomId, lastPrivateChatMessageId, size);
+    }
 }
diff --git a/src/main/java/com/mos/backend/studychatmessages/application/StudyChatMessageService.java b/src/main/java/com/mos/backend/studychatmessages/application/StudyChatMessageService.java
@@ -1,9 +1,12 @@
 package com.mos.backend.studychatmessages.application;
 
+import com.mos.backend.common.dto.InfinityScrollRes;
 import com.mos.backend.common.exception.MosException;
 import com.mos.backend.common.infrastructure.EntityFacade;
 import com.mos.backend.common.redis.RedisPublisher;
+import com.mos.backend.common.utils.InfinityScrollUtil;
 import com.mos.backend.studychatmessages.application.dto.StudyChatMessageDto;
+import com.mos.backend.studychatmessages.application.res.StudyChatMessageRes;
 import com.mos.backend.studychatmessages.entity.StudyChatMessage;
 import com.mos.backend.studychatmessages.infrastructure.StudyChatMessageRepository;
 import com.mos.backend.studychatmessages.presentation.req.StudyChatMessagePublishReq;
@@ -15,6 +18,9 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.List;
+import java.util.Optional;
+
 @RequiredArgsConstructor
 @Service
 public class StudyChatMessageService {
@@ -41,4 +47,30 @@ private StudyChatMessage saveStudyChatMessage(StudyChatMessagePublishReq req, Us
         StudyChatMessage studyChatMessage = StudyChatMessage.of(user, studyChatRoom, req.getMessage());
         return studyChatMessageRepository.save(studyChatMessage);
     }
+
+    @Transactional(readOnly = true)
+    public InfinityScrollRes<StudyChatMessageRes> getStudyChatMessages(Long userId, Long studyChatRoomId, Long lastStudyChatMessageId, Integer size) {
+        User user = entityFacade.getUser(userId);
+        StudyChatRoom studyChatRoom = entityFacade.getStudyChatRoom(studyChatRoomId);
+
+        if (!studyMemberRepository.existsByUserAndStudy(user, studyChatRoom.getStudy()))
+            throw new MosException(StudyChatRoomErrorCode.FORBIDDEN);
+
+        List<StudyChatMessage> studyChatMessages = studyChatMessageRepository.findAllByChatRoomIdForInfiniteScroll(
+                studyChatRoom.getId(), lastStudyChatMessageId, size
+        );
+
+        boolean hasNext = InfinityScrollUtil.hasNext(studyChatMessages, size);
+        if (hasNext)
+            studyChatMessages.remove(studyChatMessages.size() - 1);
+
+        Optional<StudyChatMessage> lastElement = InfinityScrollUtil.getLastElement(studyChatMessages);
+        Long lastElementId = lastElement.map(StudyChatMessage::getId).orElse(null);
+
+        List<StudyChatMessageRes> studyChatMessageResList = studyChatMessages.stream()
+                .map(StudyChatMessageRes::of)
+                .toList();
+
+        return InfinityScrollRes.of(studyChatMessageResList, lastElementId, hasNext);
+    }
 }
diff --git a/src/main/java/com/mos/backend/studychatmessages/application/res/StudyChatMessageRes.java b/src/main/java/com/mos/backend/studychatmessages/application/res/StudyChatMessageRes.java
@@ -0,0 +1,33 @@
+package com.mos.backend.studychatmessages.application.res;
+
+import com.mos.backend.studychatmessages.entity.StudyChatMessage;
+import com.mos.backend.users.entity.User;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+
+@NoArgsConstructor
+@Getter
+public class StudyChatMessageRes {
+    private Long studyChatMessageId;
+    private String message;
+    private LocalDateTime messageCreatedAt;
+
+    private Long userId;
+    private String nickname;
+
+    public static StudyChatMessageRes of(StudyChatMessage studyChatMessage) {
+        User user = studyChatMessage.getUser();
+
+        StudyChatMessageRes studyChatMessageRes = new StudyChatMessageRes();
+        studyChatMessageRes.studyChatMessageId = studyChatMessage.getId();
+        studyChatMessageRes.message = studyChatMessage.getMessage();
+        studyChatMessageRes.messageCreatedAt = studyChatMessage.getCreatedAt();
+
+        studyChatMessageRes.userId = user.getId();
+        studyChatMessageRes.nickname = user.getNickname();
+
+        return studyChatMessageRes;
+    }
+}
diff --git a/.../com/mos/backend/studychatmessages/infrastructure/StudyChatMessageQueryDslRepository.java b/.../com/mos/backend/studychatmessages/infrastructure/StudyChatMessageQueryDslRepository.java
@@ -0,0 +1,37 @@
+package com.mos.backend.studychatmessages.infrastructure;
+
+import com.mos.backend.studychatmessages.entity.StudyChatMessage;
+import com.querydsl.core.types.dsl.BooleanExpression;
+import com.querydsl.jpa.impl.JPAQueryFactory;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+
+import static com.mos.backend.studychatmessages.entity.QStudyChatMessage.studyChatMessage;
+
+@Repository
+@RequiredArgsConstructor
+public class StudyChatMessageQueryDslRepository {
+    private final JPAQueryFactory queryFactory;
+
+    public List<StudyChatMessage> findAllByChatRoomIdForInfiniteScroll(Long studyChatRoomId, Long lastStudyChatMessageId, Integer size) {
+        return queryFactory
+                .selectFrom(studyChatMessage)
+                .where(
+                        eqStudyChatRoomId(studyChatRoomId),
+                        ltStudyChatMessageId(lastStudyChatMessageId)
+                )
+                .orderBy(studyChatMessage.id.desc())
+                .limit(size + 1)
+                .fetch();
+    }
+
+    private static BooleanExpression ltStudyChatMessageId(Long lastStudyChatMessageId) {
+        return lastStudyChatMessageId == null ? null : studyChatMessage.id.lt(lastStudyChatMessageId);
+    }
+
+    private static BooleanExpression eqStudyChatRoomId(Long studyChatRoomId) {
+        return studyChatMessage.studyChatRoom.id.eq(studyChatRoomId);
+    }
+}
diff --git a/...ain/java/com/mos/backend/studychatmessages/infrastructure/StudyChatMessageRepository.java b/...ain/java/com/mos/backend/studychatmessages/infrastructure/StudyChatMessageRepository.java
@@ -2,6 +2,10 @@
 
 import com.mos.backend.studychatmessages.entity.StudyChatMessage;
 
+import java.util.List;
+
 public interface StudyChatMessageRepository {
     StudyChatMessage save(StudyChatMessage studyChatMessage);
+
+    List<StudyChatMessage> findAllByChatRoomIdForInfiniteScroll(Long studyChatRoomId, Long lastStudyChatMessageId, Integer size);
 }