feat: 익명 로그인 API 구현

src/main/java/com/potatocake/everymoment/config/SecurityConfig.java

@@ -45,7 +45,8 @@ public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
 
         http
                 .authorizeHttpRequests(auth -> auth
-                        .requestMatchers("/api/members/login", "/h2-console/**", "/error", "/favicon.ico").permitAll()
+                        .requestMatchers("/api/members/login", "/api/members/anonymous-login", "/h2-console/**",
+                                "/error", "/favicon.ico").permitAll()
                         .requestMatchers("/swagger-resources/**", "/swagger-ui/**", "/v3/api-docs/**").permitAll()
                         .anyRequest().authenticated());
 

src/main/java/com/potatocake/everymoment/config/SwaggerConfig.java

@@ -39,7 +39,7 @@ private OpenApiCustomizer addSecurityItemToAllEndpointsExceptLogin() {
         return openApi -> {
             SecurityRequirement securityRequirement = new SecurityRequirement().addList("bearerAuth");
             openApi.getPaths().forEach((path, item) -> {
-                if (!"/api/members/login".equals(path)) {
+                if (!"/api/members/login".equals(path) && !"/api/members/anonymous-login".equals(path)) {
                     item.readOperations().forEach(operation -> {
                         operation.addSecurityItem(securityRequirement);
                     });

src/main/java/com/potatocake/everymoment/controller/MemberController.java

@@ -2,6 +2,7 @@
 
 import com.potatocake.everymoment.dto.SuccessResponse;
 import com.potatocake.everymoment.dto.request.MemberLoginRequest;
+import com.potatocake.everymoment.dto.response.AnonymousLoginResponse;
 import com.potatocake.everymoment.dto.response.JwtResponse;
 import com.potatocake.everymoment.dto.response.MemberDetailResponse;
 import com.potatocake.everymoment.dto.response.MemberMyResponse;
@@ -39,6 +40,15 @@ public class MemberController {
 
     private final MemberService memberService;
 
+    @Operation(summary = "익명 로그인", description = "회원번호로 로그인하거나 새로운 익명 계정을 생성합니다.")
+    @ApiResponse(responseCode = "200", description = "익명 로그인 성공")
+    @GetMapping("/anonymous-login")
+    public ResponseEntity<SuccessResponse> anonymousLogin(@Parameter(description = "기기에 저장된 회원번호 (없을 경우 새로운 계정 생성)")
+                                                          @RequestParam(required = false) Long number) {
+        AnonymousLoginResponse response = memberService.anonymousLogin(number);
+        return ResponseEntity.ok(SuccessResponse.ok(response));
+    }
+
     @Operation(summary = "로그인", description = "회원 번호와 닉네임으로 로그인합니다.")
     @ApiResponse(responseCode = "200", description = "로그인 성공", content = @Content(schema = @Schema(implementation = JwtResponse.class)))
     @PostMapping("/login")

src/main/java/com/potatocake/everymoment/dto/response/AnonymousLoginResponse.java

@@ -0,0 +1,15 @@
+package com.potatocake.everymoment.dto.response;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import lombok.Builder;
+import lombok.Getter;
+
+@Builder
+@JsonInclude(JsonInclude.Include.NON_NULL)
+@Getter
+public class AnonymousLoginResponse {
+
+    private Long number;
+    private String token;
+
+}

src/main/java/com/potatocake/everymoment/repository/MemberRepository.java

@@ -1,11 +1,14 @@
 package com.potatocake.everymoment.repository;
 
 import com.potatocake.everymoment.entity.Member;
+import jakarta.persistence.LockModeType;
 import java.util.Optional;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Window;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
+import org.springframework.data.jpa.repository.Query;
 
 public interface MemberRepository extends JpaRepository<Member, Long> {
 
@@ -15,4 +18,8 @@ public interface MemberRepository extends JpaRepository<Member, Long> {
 
     Window<Member> findByNicknameContaining(String nickname, ScrollPosition position, Pageable pageable);
 
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("SELECT CASE WHEN MIN(m.number) > 0 OR MIN(m.number) IS NULL THEN -1 ELSE MIN(m.number) - 1 END FROM Member m")
+    Long findNextAnonymousNumber();
+
 }

src/main/java/com/potatocake/everymoment/service/MemberService.java

@@ -2,6 +2,7 @@
 
 import static org.springframework.data.domain.Sort.Direction.ASC;
 
+import com.potatocake.everymoment.dto.response.AnonymousLoginResponse;
 import com.potatocake.everymoment.dto.response.FriendRequestStatus;
 import com.potatocake.everymoment.dto.response.MemberDetailResponse;
 import com.potatocake.everymoment.dto.response.MemberMyResponse;
@@ -13,6 +14,7 @@
 import com.potatocake.everymoment.repository.FriendRepository;
 import com.potatocake.everymoment.repository.FriendRequestRepository;
 import com.potatocake.everymoment.repository.MemberRepository;
+import com.potatocake.everymoment.util.JwtUtil;
 import com.potatocake.everymoment.util.PagingUtil;
 import com.potatocake.everymoment.util.S3FileUploader;
 import java.util.List;
@@ -35,6 +37,7 @@ public class MemberService {
     private final FriendRepository friendRepository;
     private final PagingUtil pagingUtil;
     private final S3FileUploader s3FileUploader;
+    private final JwtUtil jwtUtil;
 
     @Transactional(readOnly = true)
     public MemberSearchResponse searchMembers(String nickname, Long key, int size, Long currentMemberId) {
@@ -72,6 +75,39 @@ public MemberMyResponse getMemberInfo(Long memberId) {
                 .build();
     }
 
+    public AnonymousLoginResponse anonymousLogin(Long memberNumber) {
+        if (memberNumber != null) {
+            // 기존 회원번호로 로그인 시도
+            return memberRepository.findByNumber(memberNumber)
+                    .map(member -> AnonymousLoginResponse.builder()
+                            .token(jwtUtil.create(member.getId()))
+                            .build())
+                    .orElseGet(this::createAnonymousLoginResponse);
+        }
+
+        // 새로운 익명 회원 생성 및 응답
+        return createAnonymousLoginResponse();
+    }
+
+    private AnonymousLoginResponse createAnonymousLoginResponse() {
+        Member newMember = createAnonymousMember();
+        return AnonymousLoginResponse.builder()
+                .number(newMember.getNumber())
+                .token(jwtUtil.create(newMember.getId()))
+                .build();
+    }
+
+    private Member createAnonymousMember() {
+        Long nextNumber = memberRepository.findNextAnonymousNumber();
+
+        Member member = Member.builder()
+                .nickname("Anonymous")
+                .number(nextNumber)
+                .build();
+
+        return memberRepository.save(member);
+    }
+
     public void updateMemberInfo(Long id, MultipartFile profileImage, String nickname) {
         Member member = memberRepository.findById(id)
                 .orElseThrow(() -> new GlobalException(ErrorCode.MEMBER_NOT_FOUND));