채팅 답변 생성 및 취소 API 구현

build.gradle

@@ -67,6 +67,11 @@ dependencies {
     testImplementation "org.springframework.cloud:spring-cloud-starter-openfeign"
     testImplementation "com.squareup.okhttp3:mockwebserver:4.12.0"
 
+    // WebSocket
+    implementation 'org.springframework.boot:spring-boot-starter-websocket'
+
+    // WebFlux
+    implementation 'org.springframework.boot:spring-boot-starter-webflux'
 }
 
 dependencyManagement {

src/main/java/com/sofa/linkiving/domain/chat/controller/ChatApi.java

@@ -7,9 +7,25 @@
 import com.sofa.linkiving.global.common.BaseResponse;
 
 import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.Parameter;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
-@Tag(name = "Chat", description = "채팅 관리 API")
+@Tag(name = "Chat", description = """
+	AI 채팅 통합 명세 (HTTP + WebSocket)
+
+	### 📡 1. WebSocket 연결 정보 (필수)
+		답변을 실시간으로 수신하기 위해 **반드시 소켓 연결 및 구독**이 선행되어야 합니다.
+
+		* **Socket Endpoint:** `ws://{domain}/ws/chat`
+		* **Subscribe Path:** `/topic/chat/{chatId}`
+		* **Auth Header:** `Authorization: Bearer {accessToken}` (CONNECT 프레임 헤더)
+	### 🚀 2. 동작 흐름
+		1. **소켓 연결:** 프론트엔드에서 WebSocket 연결 및 `/topic/chat/{chatId}` 구독
+		2. **질문 전송:** `/app/send/{chatId}` (STOMP)로 질문 전송
+		3. **답변 수신:** 소켓 구독 채널로 토큰 단위 답변 스트리밍 (`String` 데이터)
+		4. **완료:** `END_OF_STREAM` 메시지 수신 시 스트리밍 종료
+
+	""")
 public interface ChatApi {
 	@Operation(summary = "채팅방 목록 조회", description = "사용자의 채팅방 목록 정보(채팅방 Id, 제목)을 조회합니다.")
 	BaseResponse<ChatsRes> getChats(Member member);
@@ -19,4 +35,9 @@ BaseResponse<CreateChatRes> createChat(
 		CreateChatReq req,
 		Member member
 	);
+
+	void sendMessage(@Parameter(description = "채팅방 Id", required = true) Long chatId,
+		@Parameter(description = "사용자 질문 내용", required = true) String message, Member member);
+
+	void cancelMessage(@Parameter(description = "채팅방 Id", required = true) Long chatId, Member member);
 }

src/main/java/com/sofa/linkiving/domain/chat/controller/ChatController.java

@@ -1,5 +1,8 @@
 package com.sofa.linkiving.domain.chat.controller;
 
+import org.springframework.messaging.handler.annotation.DestinationVariable;
+import org.springframework.messaging.handler.annotation.MessageMapping;
+import org.springframework.messaging.handler.annotation.Payload;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -36,4 +39,16 @@ public BaseResponse<CreateChatRes> createChat(@RequestBody @Valid CreateChatReq
 		CreateChatRes res = chatFacade.createChat(req.firstChat(), member);
 		return BaseResponse.success(res, "채팅방 생성 완료");
 	}
+
+	@MessageMapping("/send/{chatId}")
+	@Override
+	public void sendMessage(@DestinationVariable Long chatId, @Payload String message, @AuthMember Member member) {
+		chatFacade.generateAnswer(chatId, member, message);
+	}
+
+	@MessageMapping("/cancel/{chatId}")
+	@Override
+	public void cancelMessage(@DestinationVariable Long chatId, @AuthMember Member member) {
+		chatFacade.cancelAnswer(chatId, member);
+	}
 }

src/main/java/com/sofa/linkiving/domain/chat/controller/MockAiController.java

@@ -0,0 +1,33 @@
+package com.sofa.linkiving.domain.chat.controller;
+
+import java.time.Duration;
+import java.util.Map;
+
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import reactor.core.publisher.Flux;
+
+@RestController
+@RequestMapping("/mock/ai")
+public class MockAiController {
+
+	@PostMapping(value = "/generate", produces = MediaType.APPLICATION_NDJSON_VALUE) // 또는 TEXT_EVENT_STREAM_VALUE
+	public Flux<String> generateAnswer(@RequestBody Map<String, String> request) {
+		String userPrompt = request.get("prompt");
+
+		String fakeResponse = """
+			안녕하세요! 저는 임시 AI 봇입니다. 🤖
+			현재 AI 서버가 구축되지 않아서 테스트용 답변을 드리고 있어요.
+			질문하신 내용인 "%s"에 대해 답변을 생성하는 척 하고 있습니다.
+			취소 기능을 테스트하시려면 지금 바로 취소 버튼을 눌러보세요!
+			타이핑 효과를 위해 천천히 답변을 보내고 있습니다...
+			""".formatted(userPrompt);
+
+		return Flux.fromArray(fakeResponse.split(""))
+			.delayElements(Duration.ofMillis(100));
+	}
+}

src/main/java/com/sofa/linkiving/domain/chat/error/ChatErrorCode.java

@@ -0,0 +1,20 @@
+package com.sofa.linkiving.domain.chat.error;
+
+import org.springframework.http.HttpStatus;
+
+import com.sofa.linkiving.global.error.code.ErrorCode;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@Getter
+@RequiredArgsConstructor
+public enum ChatErrorCode implements ErrorCode {
+
+	CHAT_NOT_FOUND(HttpStatus.NOT_FOUND, "C-001", "채팅을 찾을 수 없습니다."),
+	ALREADY_GENERATING(HttpStatus.BAD_REQUEST, "C-002", "현재 답변이 생성 중입니다. 잠시만 기다려주세요.");
+
+	private final HttpStatus status;
+	private final String code;
+	private final String message;
+}

src/main/java/com/sofa/linkiving/domain/chat/facade/ChatFacade.java

@@ -37,4 +37,15 @@ public ChatsRes getChats(Member member) {
 		List<Chat> chats = chatService.getChats(member);
 		return ChatsRes.from(chats);
 	}
+
+	@Transactional
+	public void generateAnswer(Long chatId, Member member, String message) {
+		Chat chat = chatService.getChat(chatId, member);
+		messageService.generateAnswer(chat, message);
+	}
+
+	public void cancelAnswer(Long chatId, Member member) {
+		Chat chat = chatService.getChat(chatId, member);
+		messageService.cancelAnswer(chat);
+	}
 }

src/main/java/com/sofa/linkiving/domain/chat/manager/SubscriptionManager.java

@@ -0,0 +1,39 @@
+package com.sofa.linkiving.domain.chat.manager;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.stereotype.Component;
+
+import reactor.core.Disposable;
+
+@Component
+public class SubscriptionManager {
+
+	private final Map<String, Disposable> activeSubscriptions = new ConcurrentHashMap<>();
+
+	/**
+	 * 구독 추가 (기존 작업이 있다면 취소 후 등록)
+	 */
+	public void add(String key, Disposable subscription) {
+		cancel(key); // 안전하게 기존 작업 정리
+		activeSubscriptions.put(key, subscription);
+	}
+
+	/**
+	 * 구독 취소 및 자원 해제
+	 */
+	public void cancel(String key) {
+		Disposable subscription = activeSubscriptions.remove(key);
+		if (subscription != null && !subscription.isDisposed()) {
+			subscription.dispose();
+		}
+	}
+
+	/**
+	 * 완료된 구독 제거 (자원 해제 없이 Map에서만 삭제)
+	 */
+	public void remove(String key) {
+		activeSubscriptions.remove(key);
+	}
+}

src/main/java/com/sofa/linkiving/domain/chat/repository/ChatRepository.java

@@ -1,6 +1,7 @@
 package com.sofa.linkiving.domain.chat.repository;
 
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;
@@ -21,4 +22,6 @@ public interface ChatRepository extends JpaRepository<Chat, Long> {
 		ORDER BY MAX(m.createdAt) DESC
 		""")
 	List<Chat> findAllByMemberOrderByLastMessageDesc(@Param("member") Member member);
+
+	Optional<Chat> findByIdAndMember(Long id, Member member);
 }

src/main/java/com/sofa/linkiving/domain/chat/service/ChatQueryService.java

@@ -5,8 +5,10 @@
 import org.springframework.stereotype.Service;
 
 import com.sofa.linkiving.domain.chat.entity.Chat;
+import com.sofa.linkiving.domain.chat.error.ChatErrorCode;
 import com.sofa.linkiving.domain.chat.repository.ChatRepository;
 import com.sofa.linkiving.domain.member.entity.Member;
+import com.sofa.linkiving.global.error.exception.BusinessException;
 
 import lombok.RequiredArgsConstructor;
 
@@ -15,6 +17,12 @@
 public class ChatQueryService {
 	private final ChatRepository chatRepository;
 
+	public Chat findChat(Long chatId, Member member) {
+		return chatRepository.findByIdAndMember(chatId, member).orElseThrow(
+			() -> new BusinessException(ChatErrorCode.CHAT_NOT_FOUND)
+		);
+	}
+
 	public List<Chat> findAllOrderByLastMessageDesc(Member member) {
 		return chatRepository.findAllByMemberOrderByLastMessageDesc(member);
 	}

src/main/java/com/sofa/linkiving/domain/chat/service/ChatService.java

@@ -8,13 +8,19 @@
 import com.sofa.linkiving.domain.member.entity.Member;
 
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 
+@Slf4j
 @Service
 @RequiredArgsConstructor
 public class ChatService {
 	private final ChatCommandService chatCommandService;
 	private final ChatQueryService chatQueryService;
 
+	public Chat getChat(Long chatId, Member member) {
+		return chatQueryService.findChat(chatId, member);
+	}
+
 	public List<Chat> getChats(Member member) {
 		return chatQueryService.findAllOrderByLastMessageDesc(member);
 	}

src/main/java/com/sofa/linkiving/domain/chat/service/MessageCommandService.java

@@ -2,6 +2,7 @@
 
 import org.springframework.stereotype.Service;
 
+import com.sofa.linkiving.domain.chat.entity.Message;
 import com.sofa.linkiving.domain.chat.repository.MessageRepository;
 
 import lombok.RequiredArgsConstructor;
@@ -10,4 +11,8 @@
 @RequiredArgsConstructor
 public class MessageCommandService {
 	private final MessageRepository messageRepository;
+
+	public Message saveMessage(Message message) {
+		return messageRepository.save(message);
+	}
 }

src/main/java/com/sofa/linkiving/domain/chat/service/MessageService.java

@@ -1,12 +1,88 @@
 package com.sofa.linkiving.domain.chat.service;
 
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.messaging.simp.SimpMessagingTemplate;
 import org.springframework.stereotype.Service;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import com.sofa.linkiving.domain.chat.entity.Chat;
+import com.sofa.linkiving.domain.chat.entity.Message;
+import com.sofa.linkiving.domain.chat.enums.Type;
+import com.sofa.linkiving.domain.chat.manager.SubscriptionManager;
 
 import lombok.RequiredArgsConstructor;
+import reactor.core.Disposable;
 
 @Service
 @RequiredArgsConstructor
 public class MessageService {
 	private final MessageCommandService messageCommandService;
 	private final MessageQueryService messageQueryService;
+
+	private final SimpMessagingTemplate messagingTemplate;
+	private final SubscriptionManager subscriptionManager;
+
+	private final WebClient webClient = WebClient.create("http://localhost:8080/mock/ai");
+	private final Map<String, StringBuilder> messageBuffers = new ConcurrentHashMap<>();
+
+	public void generateAnswer(Chat chat, String userMessage) {
+
+		String roomId = chat.getId().toString();
+
+		if (messageBuffers.containsKey(roomId)) {
+			return;
+		}
+
+		messageBuffers.put(roomId, new StringBuilder());
+
+		Disposable subscription = webClient.post()
+			.uri("/generate")
+			.bodyValue(Map.of("prompt", userMessage))
+			.retrieve()
+			.bodyToFlux(String.class)
+			.doOnComplete(() -> {
+				String fullAnswer = messageBuffers.remove(roomId).toString();
+
+				saveMessage(chat, Type.USER, userMessage);
+				saveMessage(chat, Type.AI, fullAnswer);
+
+				subscriptionManager.remove(roomId);
+				messagingTemplate.convertAndSend("/topic/chat/" + roomId, "END_OF_STREAM");
+			})
+			.doOnError(e -> {
+				subscriptionManager.remove(roomId);
+				messagingTemplate.convertAndSend("/topic/chat/" + roomId, "ERROR: " + e.getMessage());
+			})
+			.subscribe(token -> {
+				StringBuilder buffer = messageBuffers.get(roomId);
+				if (buffer != null) {
+					buffer.append(token);
+				}
+
+				messagingTemplate.convertAndSend("/topic/chat/" + roomId, token);
+			});
+
+		subscriptionManager.add(roomId, subscription);
+	}
+
+	public void cancelAnswer(Chat chat) {
+		String roomId = chat.getId().toString();
+
+		subscriptionManager.cancel(roomId);
+		messageBuffers.remove(roomId);
+
+		messagingTemplate.convertAndSend("/topic/chat/" + roomId, "GENERATION_CANCELLED");
+	}
+
+	private void saveMessage(Chat chat, Type type, String content) {
+		Message message = Message.builder()
+			.chat(chat)
+			.type(type)
+			.content(content)
+			.build();
+
+		messageCommandService.saveMessage(message);
+	}
 }

src/main/java/com/sofa/linkiving/global/config/WebMvcConfig.java

@@ -3,7 +3,10 @@
 import java.util.List;
 
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.task.AsyncTaskExecutor;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.servlet.config.annotation.AsyncSupportConfigurer;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 import com.sofa.linkiving.security.resolver.AuthMemberArgumentResolver;
@@ -20,4 +23,19 @@ public class WebMvcConfig implements WebMvcConfigurer {
 	public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
 		resolvers.add(authMemberArgumentResolver);
 	}
+
+	@Override
+	public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
+		configurer.setTaskExecutor(mvcTaskExecutor());
+	}
+
+	public AsyncTaskExecutor mvcTaskExecutor() {
+		ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+		executor.setCorePoolSize(10);
+		executor.setMaxPoolSize(100);
+		executor.setQueueCapacity(50);
+		executor.setThreadNamePrefix("mvc-async-");
+		executor.initialize();
+		return executor;
+	}
 }