Feat: 유저 닉네임 중복 체크

src/main/java/com/rabbitmqprac/application/controller/UserController.java

@@ -1,6 +1,7 @@
 package com.rabbitmqprac.application.controller;
 
 import com.rabbitmqprac.application.dto.auth.res.UserDetailRes;
+import com.rabbitmqprac.application.dto.user.req.NicknameCheckReq;
 import com.rabbitmqprac.application.dto.user.req.NicknameUpdateReq;
 import com.rabbitmqprac.domain.context.user.service.UserService;
 import com.rabbitmqprac.infra.security.authentication.SecurityUserDetails;
@@ -46,4 +47,8 @@ public ResponseEntity<Void> patchNickname(@AuthenticationPrincipal SecurityUserD
         return ResponseEntity.noContent().build();
     }
 
+    @GetMapping("/users/nickname")
+    public Map<String, Boolean> checkNicknameDuplication(@Validated NicknameCheckReq nicknameCheckReq) {
+        return Map.of("isDuplicated", userService.isDuplicatedNickname(nicknameCheckReq));
+    }
 }

src/main/java/com/rabbitmqprac/application/dto/user/req/NicknameCheckReq.java

@@ -0,0 +1,9 @@
+package com.rabbitmqprac.application.dto.user.req;
+
+import com.rabbitmqprac.global.annotation.Nickname;
+
+public record NicknameCheckReq(
+        @Nickname
+        String nickname
+) {
+}

src/main/java/com/rabbitmqprac/domain/context/user/service/UserService.java

@@ -2,6 +2,7 @@
 
 
 import com.rabbitmqprac.application.dto.auth.res.UserDetailRes;
+import com.rabbitmqprac.application.dto.user.req.NicknameCheckReq;
 import com.rabbitmqprac.application.dto.user.req.NicknameUpdateReq;
 import com.rabbitmqprac.application.mapper.UserMapper;
 import com.rabbitmqprac.domain.context.user.dto.req.UserCreateReq;
@@ -91,4 +92,9 @@ public User create(String nickname) {
         User user = User.of(nickname, Role.USER);
         return userRepository.save(user);
     }
+
+    @Transactional(readOnly = true)
+    public boolean isDuplicatedNickname(NicknameCheckReq req) {
+        return userRepository.existsByNickname(req.nickname());
+    }
 }

src/test/java/com/rabbitmqprac/service/UserServiceTest.java

@@ -1,6 +1,7 @@
 package com.rabbitmqprac.service;
 
 import com.rabbitmqprac.application.dto.auth.res.UserDetailRes;
+import com.rabbitmqprac.application.dto.user.req.NicknameCheckReq;
 import com.rabbitmqprac.application.dto.user.req.NicknameUpdateReq;
 import com.rabbitmqprac.common.fixture.UserFixture;
 import com.rabbitmqprac.domain.context.user.dto.req.UserCreateReq;
@@ -9,6 +10,7 @@
 import com.rabbitmqprac.domain.context.user.service.UserService;
 import com.rabbitmqprac.domain.persistence.user.entity.User;
 import com.rabbitmqprac.domain.persistence.user.repository.UserRepository;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
@@ -279,4 +281,41 @@ void isDuplicatedUsernameFalse() {
         }
     }
 
+    @Nested
+    @DisplayName("닉네임 중복 체크 성공 시나리오")
+    class NicknameDuplicateCheckSuccessScenarios {
+        private static NicknameCheckReq req = mock(NicknameCheckReq.class);
+
+        @BeforeEach
+        void setUp() {
+            given(req.nickname()).willReturn(user.getNickname());
+        }
+
+        @Test
+        @DisplayName("닉네임 중복 체크 - 중복")
+        void isDuplicatedNicknameTrue() {
+            // given
+            given(userRepository.existsByNickname(user.getNickname())).willReturn(Boolean.TRUE);
+
+            // when
+            Boolean result = userService.isDuplicatedNickname(req);
+
+            // then
+            assertThat(result).isTrue();
+        }
+
+        @Test
+        @DisplayName("닉네임 중복 체크 - 중복 아님")
+        void isDuplicatedNicknameFalse() {
+            // given
+            given(userRepository.existsByNickname(user.getNickname())).willReturn(Boolean.FALSE);
+
+            // when
+            Boolean result = userService.isDuplicatedNickname(req);
+
+            // then
+            assertThat(result).isFalse();
+        }
+    }
+
 }