✨ feat: 닉네임 중복 확인 기능

Author: jiwon1217

backend/src/main/java/io/f1/backend/domain/user/api/SignupController.java

@@ -10,8 +10,10 @@
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 
 @RestController
@@ -26,4 +28,10 @@ public ResponseEntity<CurrentUserAndAdminResponse> completeSignup(
         CurrentUserAndAdminResponse response = userService.signup(httpSession, signupRequest);
         return ResponseEntity.status(HttpStatus.CREATED).body(response);
     }
+
+    @GetMapping("/check-nickname")
+    public ResponseEntity<Void> checkNicknameDuplicate(@RequestParam String nickname) {
+        userService.checkNickname(nickname);
+        return ResponseEntity.ok().build();
+    }
 }

backend/src/main/java/io/f1/backend/domain/user/app/UserService.java

@@ -31,11 +31,7 @@ public class UserService {
     public CurrentUserAndAdminResponse signup(HttpSession session, SignupRequest signupRequest) {
         AuthenticationUser authenticationUser = extractSessionUser(session);
 
-        String nickname = signupRequest.nickname();
-        validateNicknameFormat(nickname);
-        validateNicknameDuplicate(nickname);
-
-        User user = initNickname(authenticationUser.userId(), nickname);
+        User user = initNickname(authenticationUser.userId(), signupRequest.nickname());
         updateSessionAfterSignup(session, user);
 
         SecurityUtils.setAuthentication(user);
@@ -99,11 +95,14 @@ public void deleteUser(Long userId) {
 
     @Transactional
     public void updateNickname(Long userId, String newNickname, HttpSession session) {
-        validateNicknameFormat(newNickname);
-        validateNicknameDuplicate(newNickname);
-
         User user = initNickname(userId, newNickname);
         session.setAttribute(USER, AuthenticationUser.from(user));
         SecurityUtils.setAuthentication(user);
     }
+
+    @Transactional(readOnly = true)
+    public void checkNickname(String nickname) {
+        validateNicknameFormat(nickname);
+        validateNicknameDuplicate(nickname);
+    }
 }