🐛 Fix: users - club 연관관계 오류 수정

src/main/java/com/be/sportizebe/domain/club/dto/request/ClubCreateRequest.java

@@ -2,7 +2,6 @@
 
 import com.be.sportizebe.domain.club.entity.Club;
 import com.be.sportizebe.domain.user.entity.SportType;
-import com.be.sportizebe.domain.user.entity.User;
 import io.swagger.v3.oas.annotations.media.Schema;
 import jakarta.validation.constraints.NotBlank;
 
@@ -13,14 +12,13 @@ public record ClubCreateRequest(
   @Schema(description = "동호회 관련 종목", example = "SOCCER") SportType clubType,
   @Schema(description = "최대 정원", example = "20") Integer maxMembers) {
 
-  public Club toEntity(User user, String clubImage) {
+  public Club toEntity(String clubImage) {
     return Club.builder()
       .name(name)
       .introduce(introduce)
       .clubType(clubType)
       .maxMembers(maxMembers)
       .clubImage(clubImage)
-      .leader(user)
       .build();
   }
 }

src/main/java/com/be/sportizebe/domain/club/entity/Club.java

@@ -39,17 +39,40 @@ public class Club extends BaseTimeEntity {
 
   private String clubImage; // 동호회 사진 URL
 
-  @ManyToOne(fetch = FetchType.LAZY)
-  @JoinColumn(name = "leader_id", nullable = false)
-  private User leader; // 동호회장
-
   @OneToOne(mappedBy = "club", fetch = FetchType.LAZY)
   private ChatRoom chatRoom; // 동호회 채팅방
 
   @OneToMany(mappedBy = "club", cascade = CascadeType.ALL, orphanRemoval = true)
   @Builder.Default
   private List<ClubMember> members = new ArrayList<>();
 
+  /**
+   * 동호회장(LEADER) 조회
+   * ClubMember에서 LEADER 역할을 가진 멤버를 찾아 반환
+   */
+  public ClubMember getLeaderMember() {
+    return members.stream()
+        .filter(member -> member.getRole() == ClubMember.ClubRole.LEADER)
+        .findFirst()
+        .orElse(null);
+  }
+
+  /**
+   * 동호회장 User 조회
+   */
+  public User getLeader() {
+    ClubMember leaderMember = getLeaderMember();
+    return leaderMember != null ? leaderMember.getUser() : null;
+  }
+
+  /**
+   * 특정 사용자가 동호회장인지 확인
+   */
+  public boolean isLeader(Long userId) {
+    ClubMember leaderMember = getLeaderMember();
+    return leaderMember != null && leaderMember.getUser().getId() == userId;
+  }
+
   public void update(String name, String introduce, Integer maxMembers, SportType clubType) {
     this.name = name;
     this.introduce = introduce;

src/main/java/com/be/sportizebe/domain/club/service/ClubServiceImpl.java

@@ -49,7 +49,7 @@ public ClubResponse createClub(ClubCreateRequest request, MultipartFile image, L
     }
 
     // 동호회 엔티티 생성
-    Club club = request.toEntity(user, clubImageUrl);
+    Club club = request.toEntity(clubImageUrl);
     clubRepository.save(club);
 
     // 동호회 멤버 테이블에 방장(동호회 생성자) 추가
@@ -58,6 +58,7 @@ public ClubResponse createClub(ClubCreateRequest request, MultipartFile image, L
         .user(user)
         .role(ClubMember.ClubRole.LEADER)
         .build();
+    club.getMembers().add(leaderMember);
     clubMemberRepository.save(leaderMember);
 
     // 동호회 단체 채팅방 생성
@@ -73,7 +74,7 @@ public ClubResponse updateClub(Long clubId, ClubUpdateRequest request, Long user
         .orElseThrow(() -> new CustomException(ClubErrorCode.CLUB_NOT_FOUND));
 
     // 동호회 방장만 수정 가능하도록 검증
-    if (club.getLeader().getId() != userId) {
+    if (!club.isLeader(userId)) {
       throw new CustomException(ClubErrorCode.CLUB_UPDATE_DENIED);
     }
 
@@ -97,7 +98,7 @@ public ClubImageResponse updateClubImage(Long clubId, MultipartFile image, Long
         .orElseThrow(() -> new CustomException(ClubErrorCode.CLUB_NOT_FOUND));
 
     // 동호회 방장만 수정 가능하도록 검증
-    if (club.getLeader().getId() != userId) {
+    if (!club.isLeader(userId)) {
       throw new CustomException(ClubErrorCode.CLUB_UPDATE_DENIED);
     }
 

src/main/java/com/be/sportizebe/domain/notification/entity/JoinClubRequest.java

@@ -0,0 +1,54 @@
+package com.be.sportizebe.domain.notification.entity;
+
+import com.be.sportizebe.domain.club.entity.Club;
+import com.be.sportizebe.domain.user.entity.User;
+import com.be.sportizebe.global.common.BaseTimeEntity;
+import jakarta.persistence.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@Builder
+@AllArgsConstructor
+@NoArgsConstructor
+@Table(name = "join_club_request", uniqueConstraints = {
+    @UniqueConstraint(columnNames = {"user_id", "club_id"})
+})
+public class JoinClubRequest extends BaseTimeEntity {
+
+  public enum JoinClubRequestStatus {
+    PENDING,   // 대기
+    ACCEPTED,  // 승인
+    REJECTED   // 거절
+  }
+
+  @Id
+  @GeneratedValue(strategy = GenerationType.IDENTITY)
+  private Long id;
+
+  @ManyToOne(fetch = FetchType.LAZY)
+  @JoinColumn(name = "user_id", nullable = false)
+  private User user; // 가입 신청자
+
+  @ManyToOne(fetch = FetchType.LAZY)
+  @JoinColumn(name = "club_id", nullable = false)
+  private Club club; // 가입 신청 대상 동호회
+
+  @Enumerated(EnumType.STRING)
+  @Column(nullable = false)
+  @Builder.Default
+  private JoinClubRequestStatus status = JoinClubRequestStatus.PENDING;
+
+  // 가입 승인 시 상태 변경
+  public void accept() {
+    this.status = JoinClubRequestStatus.ACCEPTED;
+  }
+
+  // 가입 거절 시 상태 변경
+  public void reject() {
+    this.status = JoinClubRequestStatus.REJECTED;
+  }
+}

src/main/java/com/be/sportizebe/domain/notification/entity/Notification.java

@@ -0,0 +1,61 @@
+package com.be.sportizebe.domain.notification.entity;
+
+import com.be.sportizebe.domain.user.entity.User;
+import com.be.sportizebe.global.common.BaseTimeEntity;
+import jakarta.persistence.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@Builder
+@AllArgsConstructor
+@NoArgsConstructor
+@Table(name = "notifications", indexes = {
+    @Index(name = "idx_notification_receiver", columnList = "receiver_id"),
+    @Index(name = "idx_notification_is_read", columnList = "receiver_id, is_read")
+})
+public class Notification extends BaseTimeEntity {
+
+  public enum NotificationType {
+    JOIN_REQUEST,   // 가입 신청 (동호회장에게)
+    JOIN_APPROVED,  // 가입 승인 (신청자에게)
+    JOIN_REJECTED,  // 가입 거절 (신청자에게)
+    CHAT,           // 새 채팅 메시지
+    COMMENT         // 새 댓글
+  }
+
+  @Id
+  @GeneratedValue(strategy = GenerationType.IDENTITY)
+  private Long id;
+
+  @ManyToOne(fetch = FetchType.LAZY)
+  @JoinColumn(name = "receiver_id", nullable = false)
+  private User receiver; // 알림 수신자
+
+  @Enumerated(EnumType.STRING)
+  @Column(nullable = false)
+  private NotificationType type;
+
+  @Column(nullable = false)
+  private String message; // 알림 메시지
+
+  @Column(nullable = false)
+  @Builder.Default
+  private Boolean isRead = false;
+
+  // 가입 신청 관련 알림용 (JOIN_REQUEST, JOIN_APPROVED, JOIN_REJECTED)
+  @ManyToOne(fetch = FetchType.LAZY)
+  @JoinColumn(name = "join_request_id")
+  private JoinClubRequest joinClubRequest;
+
+  // 댓글 알림용 - targetId와 targetType으로 다형성 처리
+  // COMMENT: postId, CHAT: chatRoomId 등
+  private Long targetId;
+
+  public void markAsRead() {
+    this.isRead = true;
+  }
+}

src/main/java/com/be/sportizebe/domain/user/entity/User.java

@@ -1,5 +1,6 @@
 package com.be.sportizebe.domain.user.entity;
 
+import com.be.sportizebe.domain.club.entity.ClubMember;
 import com.be.sportizebe.domain.post.entity.Post;
 import com.be.sportizebe.global.common.BaseTimeEntity;
 import com.fasterxml.jackson.annotation.JsonIgnore;
@@ -62,6 +63,10 @@ public class User extends BaseTimeEntity {
     @Builder.Default
     private List<Post> posts = new ArrayList<>(); // 작성한 게시글 목록
 
+    @OneToMany(mappedBy = "user")
+    @Builder.Default
+    private List<ClubMember> clubMemberships = new ArrayList<>(); // 가입한 동호회 목록
+
     public void updateRefreshToken(String refreshToken) {
         this.refreshToken = refreshToken;
     }