feature: 로그인 api 추가 (#34)

src/main/java/com/goldbalance/dive/domain/member/api/MemberController.java

@@ -1,5 +1,6 @@
 package com.goldbalance.dive.domain.member.api;
 
+import com.goldbalance.dive.domain.member.dto.MemberLogin;
 import com.goldbalance.dive.domain.member.dto.request.MemberSignin;
 import com.goldbalance.dive.domain.member.service.MemberService;
 import jakarta.validation.Valid;
@@ -23,4 +24,10 @@ public ResponseEntity<Void> signin(@Valid @RequestBody MemberSignin request) {
         memberService.signin(request);
         return ResponseEntity.status(HttpStatusCode.valueOf(201)).build();
     }
+
+    @PostMapping("/login")
+    public ResponseEntity<MemberLogin> login(@Valid @RequestBody MemberLogin request) {
+        MemberLogin response = memberService.login(request);
+        return ResponseEntity.ok(response);
+    }
 }

src/main/java/com/goldbalance/dive/domain/member/dto/MemberLogin.java

@@ -0,0 +1,10 @@
+package com.goldbalance.dive.domain.member.dto;
+
+import com.goldbalance.dive.domain.member.domain.Member;
+import jakarta.validation.constraints.NotBlank;
+
+public record MemberLogin(@NotBlank String nickname) {
+    public static MemberLogin from(Member member) {
+        return new MemberLogin(member.getNickname());
+    }
+}

src/main/java/com/goldbalance/dive/domain/member/repository/MemberRepository.java

@@ -1,8 +1,11 @@
 package com.goldbalance.dive.domain.member.repository;
 
 import com.goldbalance.dive.domain.member.domain.Member;
+import java.util.Optional;
 import org.springframework.data.jpa.repository.JpaRepository;
 
 public interface MemberRepository extends JpaRepository<Member, Long> {
     boolean existsByNickname(String nickname);
+
+    Optional<Member> findByNickname(String nickname);
 }

src/main/java/com/goldbalance/dive/domain/member/service/MemberService.java

@@ -1,10 +1,12 @@
 package com.goldbalance.dive.domain.member.service;
 
+import static com.goldbalance.dive.global.exception.ErrorCode.*;
+
 import com.goldbalance.dive.domain.member.domain.Member;
+import com.goldbalance.dive.domain.member.dto.MemberLogin;
 import com.goldbalance.dive.domain.member.dto.request.MemberSignin;
 import com.goldbalance.dive.domain.member.repository.MemberRepository;
 import com.goldbalance.dive.global.exception.CustomException;
-import com.goldbalance.dive.global.exception.ErrorCode;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
@@ -22,12 +24,21 @@ public class MemberService {
     public void signin(MemberSignin request) {
         boolean isDuplicate = memberRepository.existsByNickname(request.nickname());
         if (isDuplicate) {
-            throw new CustomException(ErrorCode.MEMBER_NICKNAME_DUPLICATE);
+            throw new CustomException(MEMBER_NICKNAME_DUPLICATE);
         }
 
         Member member = Member.create(request.nickname());
         memberRepository.save(member);
 
         log.info("[MemberService] 멤버 회원가입 memberId = {}", member.getId());
     }
+
+    public MemberLogin login(MemberLogin request) {
+        Member member = memberRepository
+                .findByNickname(request.nickname())
+                .orElseThrow(() -> new CustomException(MEMBER_NOT_FOUND));
+
+        log.info("[MemberService] 멤버 로그인 memberId = {}", member.getId());
+        return MemberLogin.from(member);
+    }
 }

src/main/java/com/goldbalance/dive/global/exception/ErrorCode.java

@@ -10,7 +10,8 @@ public enum ErrorCode {
     INTERNAL_SERVER_ERROR(HttpStatus.INTERNAL_SERVER_ERROR, "서버 에러입니다."),
 
     // Member
-    MEMBER_NICKNAME_DUPLICATE(HttpStatus.BAD_REQUEST, "이미 존재하는 닉네임입니다.");
+    MEMBER_NICKNAME_DUPLICATE(HttpStatus.BAD_REQUEST, "이미 존재하는 닉네임입니다."),
+    MEMBER_NOT_FOUND(HttpStatus.NOT_FOUND, "존재하지 않는 멤버입니다.");
 
     private final HttpStatus status;
     private final String message;