[NAYB-156] feat: 사용자는 서비스와 연관된 알림을 받아볼 수 있다.

src/main/java/com/prgrms/nabmart/domain/notification/Notification.java

@@ -0,0 +1,54 @@
+package com.prgrms.nabmart.domain.notification;
+
+import com.prgrms.nabmart.domain.notification.exception.InvalidNotificationException;
+import com.prgrms.nabmart.global.BaseTimeEntity;
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.EnumType;
+import jakarta.persistence.Enumerated;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import java.util.Objects;
+import lombok.AccessLevel;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class Notification extends BaseTimeEntity {
+
+    private static final int CONTENT_LENGTH = 50;
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long notificationId;
+
+    @Column(nullable = false)
+    private String content;
+
+    @Enumerated(EnumType.STRING)
+    private NotificationType notificationType;
+
+    @Column(nullable = false)
+    private Long userId;
+
+    @Builder
+    public Notification(
+        String content,
+        Long userId,
+        NotificationType notificationType) {
+        validateContent(content);
+        this.content = content;
+        this.notificationType = notificationType;
+        this.userId = userId;
+    }
+
+    private void validateContent(String content) {
+        if(Objects.nonNull(content) && content.length() > CONTENT_LENGTH) {
+            throw new InvalidNotificationException("내용의 길이는 50자 이하여야 합니다.");
+        }
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/NotificationType.java

@@ -0,0 +1,13 @@
+package com.prgrms.nabmart.domain.notification;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@Getter
+@RequiredArgsConstructor
+public enum NotificationType {
+    CONNECT("connect"),
+    DELIVERY("delivery");
+
+    private final String value;
+}

src/main/java/com/prgrms/nabmart/domain/notification/controller/NotificationController.java

@@ -0,0 +1,31 @@
+package com.prgrms.nabmart.domain.notification.controller;
+
+import com.prgrms.nabmart.domain.notification.controller.request.ConnectNotificationCommand;
+import com.prgrms.nabmart.domain.notification.service.NotificationService;
+import com.prgrms.nabmart.global.auth.LoginUser;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+@RestController
+@RequiredArgsConstructor
+@RequestMapping("/api/v1/notifications")
+public class NotificationController {
+
+    private final NotificationService notificationService;
+
+    @GetMapping(value = "/connect", produces = "text/event-stream")
+    public ResponseEntity<SseEmitter> sseConnection(
+        @RequestHeader(value = "Last-Event-ID", required = false, defaultValue = "") String lastEventId,
+        @LoginUser Long userId) {
+
+        ConnectNotificationCommand connectNotificationCommand
+            = ConnectNotificationCommand.of(userId, lastEventId);
+        SseEmitter sseEmitter = notificationService.connectNotification(connectNotificationCommand);
+        return ResponseEntity.ok(sseEmitter);
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/controller/request/ConnectNotificationCommand.java

@@ -0,0 +1,8 @@
+package com.prgrms.nabmart.domain.notification.controller.request;
+
+public record ConnectNotificationCommand(Long userId, String lastEventId) {
+
+    public static ConnectNotificationCommand of(final Long userId, final String lastEventId) {
+        return new ConnectNotificationCommand(userId, lastEventId);
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/exception/InvalidNotificationException.java

@@ -0,0 +1,10 @@
+package com.prgrms.nabmart.domain.notification.exception;
+
+import com.prgrms.nabmart.domain.notification.exception.NotificationException;
+
+public class InvalidNotificationException extends NotificationException {
+
+    public InvalidNotificationException(String message) {
+        super(message);
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/exception/NotificationException.java

@@ -0,0 +1,8 @@
+package com.prgrms.nabmart.domain.notification.exception;
+
+public abstract class NotificationException extends RuntimeException {
+
+    public NotificationException(String message) {
+        super(message);
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/repository/EmitterMemoryRepository.java

@@ -0,0 +1,31 @@
+package com.prgrms.nabmart.domain.notification.repository;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
+import org.springframework.stereotype.Repository;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+@Repository
+public class EmitterMemoryRepository implements EmitterRepository {
+
+    private final Map<String, SseEmitter> emitters = new ConcurrentHashMap<>();
+
+    @Override
+    public void save(String emitterId, SseEmitter sseEmitter) {
+        emitters.put(emitterId, sseEmitter);
+    }
+
+    @Override
+    public void deleteById(String emitterId) {
+        emitters.remove(emitterId);
+    }
+
+    @Override
+    public Map<String, SseEmitter> findAllByIdStartWith(Long userId) {
+        String emitterIdPrefix = userId + "_";
+        return emitters.entrySet().stream()
+            .filter(entry -> entry.getKey().startsWith(emitterIdPrefix))
+            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/repository/EmitterRepository.java

@@ -0,0 +1,13 @@
+package com.prgrms.nabmart.domain.notification.repository;
+
+import java.util.Map;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+public interface EmitterRepository {
+
+    void save(String emitterId, SseEmitter sseEmitter);
+
+    void deleteById(String emitterId);
+
+    Map<String, SseEmitter> findAllByIdStartWith(Long userId);
+}

src/main/java/com/prgrms/nabmart/domain/notification/repository/NotificationRepository.java

@@ -0,0 +1,8 @@
+package com.prgrms.nabmart.domain.notification.repository;
+
+import com.prgrms.nabmart.domain.notification.Notification;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface NotificationRepository extends JpaRepository<Notification, Long> {
+
+}

src/main/java/com/prgrms/nabmart/domain/notification/service/NotificationService.java

@@ -0,0 +1,104 @@
+package com.prgrms.nabmart.domain.notification.service;
+
+import static java.text.MessageFormat.format;
+
+import com.prgrms.nabmart.domain.notification.Notification;
+import com.prgrms.nabmart.domain.notification.NotificationType;
+import com.prgrms.nabmart.domain.notification.controller.request.ConnectNotificationCommand;
+import com.prgrms.nabmart.domain.notification.repository.EmitterRepository;
+import com.prgrms.nabmart.domain.notification.repository.NotificationRepository;
+import com.prgrms.nabmart.domain.notification.service.request.SendNotificationCommand;
+import com.prgrms.nabmart.domain.notification.service.response.NotificationResponse;
+import com.prgrms.nabmart.domain.user.exception.NotFoundUserException;
+import com.prgrms.nabmart.domain.user.repository.UserRepository;
+import jakarta.transaction.Transactional;
+import java.io.IOException;
+import java.util.Map;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class NotificationService {
+
+    private static final Long DEFAULT_TIMEOUT = 60L * 1000 * 120;
+
+    private final EmitterRepository emitterRepository;
+    private final NotificationRepository notificationRepository;
+    private final UserRepository userRepository;
+
+    public SseEmitter connectNotification(ConnectNotificationCommand connectNotificationCommand) {
+        Long userId = connectNotificationCommand.userId();
+        String lastEventId = connectNotificationCommand.lastEventId();
+
+        String emitterId = format("{0}_{1}",userId, System.currentTimeMillis());
+        SseEmitter emitter = new SseEmitter(DEFAULT_TIMEOUT);
+        emitterRepository.save(emitterId, emitter);
+
+        emitter.onCompletion(() -> emitterRepository.deleteById(emitterId));
+        emitter.onTimeout(() -> emitterRepository.deleteById(emitterId));
+        emitter.onError(e -> emitterRepository.deleteById(emitterId));
+
+        // 연결 직후 데이터 전송이 없으면 503 에러 발생. 에러 방지용 더미 데이터 전송
+        send(emitter, emitterId, format("[Connected] UserId={0}", userId));
+
+        // 클라이언트 미수신한 event를 모두 전송
+        if (!connectNotificationCommand.lastEventId().isEmpty()) {
+            Map<String, SseEmitter> events = emitterRepository.findAllByIdStartWith(userId);
+            events.entrySet().stream().filter(entry -> lastEventId.compareTo(entry.getKey()) < 0)
+                .forEach(entry -> send(emitter, entry.getKey(), entry.getValue()));
+        }
+
+        return emitter;
+    }
+
+    private void send(SseEmitter emitter, String emitterId, Object data) {
+        try {
+            emitter.send(SseEmitter.event()
+                .id(emitterId)
+                .data(data));
+        } catch (IOException ex) {
+            emitterRepository.deleteById(emitterId);
+            log.error("알림 전송에 실패했습니다.", ex);
+        }
+    }
+
+    @Transactional
+    public void sendNotification(SendNotificationCommand sendNotificationCommand) {
+        Long userId = sendNotificationCommand.userId();
+        String content = sendNotificationCommand.content();
+        NotificationType notificationType = sendNotificationCommand.notificationType();
+
+        verifyExistsUser(userId);
+        Notification notification = Notification.builder()
+            .content(content)
+            .userId(userId)
+            .notificationType(notificationType)
+            .build();
+        notificationRepository.save(notification);
+
+        Map<String, SseEmitter> emitters = emitterRepository.findAllByIdStartWith(userId);
+        emitters.forEach((key, emitter) -> {
+            send(emitter, key, NotificationResponse.from(notification));
+        });
+    }
+
+    private void verifyExistsUser(Long userId) {
+        userRepository.findById(userId)
+            .orElseThrow(() -> new NotFoundUserException("존재하지 않는 유저입니다."));
+    }
+
+    private void send(SseEmitter emitter, String emitterId, NotificationResponse data) {
+        try {
+            emitter.send(SseEmitter.event()
+                .id(emitterId)
+                .name(data.notificationType().getValue())
+                .data(data));
+        } catch (IOException ex) {
+            emitterRepository.deleteById(emitterId);
+        }
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/service/request/SendNotificationCommand.java

@@ -0,0 +1,16 @@
+package com.prgrms.nabmart.domain.notification.service.request;
+
+import com.prgrms.nabmart.domain.notification.NotificationType;
+
+public record SendNotificationCommand(
+    Long userId,
+    String content,
+    NotificationType notificationType) {
+
+    public static SendNotificationCommand of(
+        final Long userId,
+        final String content,
+        final NotificationType notificationType) {
+        return new SendNotificationCommand(userId, content, notificationType);
+    }
+}

src/main/java/com/prgrms/nabmart/domain/notification/service/response/NotificationResponse.java

@@ -0,0 +1,22 @@
+package com.prgrms.nabmart.domain.notification.service.response;
+
+import com.prgrms.nabmart.domain.notification.Notification;
+import com.prgrms.nabmart.domain.notification.NotificationType;
+import java.time.LocalDateTime;
+
+public record NotificationResponse(
+    Long notificationId,
+    String content,
+    NotificationType notificationType,
+    Long userId,
+    LocalDateTime createdAt) {
+
+    public static NotificationResponse from(Notification notification) {
+        return new NotificationResponse(
+            notification.getNotificationId(),
+            notification.getContent(),
+            notification.getNotificationType(),
+            notification.getUserId(),
+            notification.getCreatedAt());
+    }
+}

src/main/java/com/prgrms/nabmart/global/config/WebMvcConfig.java

@@ -4,6 +4,7 @@
 import java.util.List;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.servlet.config.annotation.CorsRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 @Configuration
@@ -13,4 +14,13 @@ public class WebMvcConfig implements WebMvcConfigurer {
     public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
         resolvers.add(new LoginUserArgumentResolver());
     }
+
+    @Override
+    public void addCorsMappings(CorsRegistry registry) {
+        registry.addMapping("/**")
+            .allowedOrigins("http://localhost:3000")
+            .allowedHeaders("*")
+            .allowedMethods("GET", "POST", "PUT", "DELETE", "PATCH", "OPTIONS")
+            .allowCredentials(true);
+    }
 }

src/main/java/com/prgrms/nabmart/global/config/WebSecurityConfig.java

@@ -65,6 +65,7 @@ public SecurityFilterChain filterChain(
 
     private RequestMatcher[] requestPermitAll() {
         List<RequestMatcher> requestMatchers = List.of(
+            antMatcher(GET, "/api/v1/notifications/**"),
             antMatcher(POST, "/oauth2/authorization/**"),
             antMatcher(POST, "/api/v1/riders/**"),
             antMatcher(GET, "/api/v1/categories/**"),

src/test/java/com/prgrms/nabmart/base/BaseControllerTest.java

@@ -11,6 +11,7 @@
 import com.prgrms.nabmart.domain.event.service.EventService;
 import com.prgrms.nabmart.domain.item.service.ItemService;
 import com.prgrms.nabmart.domain.item.service.LikeItemService;
+import com.prgrms.nabmart.domain.notification.service.NotificationService;
 import com.prgrms.nabmart.domain.order.service.OrderService;
 import com.prgrms.nabmart.domain.payment.service.PaymentClient;
 import com.prgrms.nabmart.domain.payment.service.PaymentService;
@@ -100,6 +101,9 @@ public abstract class BaseControllerTest {
     @MockBean
     protected RiderAuthenticationService riderAuthenticationService;
 
+    @MockBean
+    protected NotificationService notificationService;
+
     protected static final String AUTHORIZATION = "Authorization";