diff --git a/src/main/java/org/hydev/clock_api/controller/RegistryExceptionHandler.java b/src/main/java/org/hydev/clock_api/controller/CommonExceptionHandler.java
similarity index 96%
rename from src/main/java/org/hydev/clock_api/controller/RegistryExceptionHandler.java
rename to src/main/java/org/hydev/clock_api/controller/CommonExceptionHandler.java
index 6a02879..b120d13 100644
--- a/src/main/java/org/hydev/clock_api/controller/RegistryExceptionHandler.java
+++ b/src/main/java/org/hydev/clock_api/controller/CommonExceptionHandler.java
@@ -11,7 +11,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 @RestControllerAdvice
-public class RegistryExceptionHandler {
+public class CommonExceptionHandler {
     @ExceptionHandler(ConstraintViolationException.class)
     // ConstraintViolationException will be wrapped to TransactionSystemException!
     // https://stackoverflow.com/questions/45070642/springboot-doesnt-handle-org-hibernate-exception-constraintviolationexception
diff --git a/src/main/java/org/hydev/clock_api/controller/RegistryControllerAspect.java b/src/main/java/org/hydev/clock_api/controller/RegistryControllerAspect.java
deleted file mode 100644
index 8037804..0000000
--- a/src/main/java/org/hydev/clock_api/controller/RegistryControllerAspect.java
+++ /dev/null
@@ -1,32 +0,0 @@
-package org.hydev.clock_api.controller;
-
-import org.aspectj.lang.ProceedingJoinPoint;
-import org.aspectj.lang.annotation.Around;
-import org.aspectj.lang.annotation.Aspect;
-import org.hydev.clock_api.error.ErrorCode;
-import org.hydev.clock_api.repository.UserRepository;
-import org.springframework.http.HttpStatus;
-import org.springframework.http.ResponseEntity;
-import org.springframework.stereotype.Component;
-
-import java.util.List;
-
-@Aspect
-@Component
-public class RegistryControllerAspect {
-    private final UserRepository userRepository;
-
-    public RegistryControllerAspect(UserRepository userRepository) {
-        this.userRepository = userRepository;
-    }
-
-    @Around(value = "execution(* RegistryController.register(String, String)) " +
-            "&& args(username, password)", argNames = "pjp, username, password")
-    // Even if I'm not use the password argument, I still should write it out!
-    private Object checkUsernameExists(ProceedingJoinPoint pjp, String username, String password) throws Throwable {
-        if (userRepository.existsByUsername(username))
-            return ResponseEntity.status(HttpStatus.NOT_ACCEPTABLE)
-                    .body(List.of(ErrorCode.USER_NAME_ALREADY_EXISTS));
-        return pjp.proceed();
-    }
-}
diff --git a/src/main/java/org/hydev/clock_api/controller/RegistryController.java b/src/main/java/org/hydev/clock_api/controller/UserController.java
similarity index 90%
rename from src/main/java/org/hydev/clock_api/controller/RegistryController.java
rename to src/main/java/org/hydev/clock_api/controller/UserController.java
index 9f2f2af..27d9e8c 100644
--- a/src/main/java/org/hydev/clock_api/controller/RegistryController.java
+++ b/src/main/java/org/hydev/clock_api/controller/UserController.java
@@ -15,15 +15,16 @@ import org.springframework.web.bind.annotation.RestController;
 
 import javax.validation.constraints.NotNull;
 import javax.validation.constraints.Pattern;
+import java.util.List;
 
 @Validated
 @RestController
 @RequestMapping("/user")
-public class RegistryController {
+public class UserController {
     private final UserRepository userRepository;
 
     @Autowired
-    public RegistryController(UserRepository userRepository) {
+    public UserController(UserRepository userRepository) {
         this.userRepository = userRepository;
     }
 
@@ -41,7 +42,9 @@ public class RegistryController {
             @RequestHeader String password
     ) {
         // First, spring will check args. If not pass there regex, raise ConstraintViolationException.
-        // Then, the aspect will check username if already exists.
+        // Check if username not exists.
+        if (userRepository.existsByUsername(username))
+            return ResponseEntity.status(HttpStatus.NOT_ACCEPTABLE).body(ErrorCode.USER_NAME_ALREADY_EXISTS);
 
         User user = new User();
         user.setUsername(username);