修正版本

src/main/java/co/jp/app/service/UserService.java

@@ -33,7 +33,7 @@ public class UserService implements UserDetailsService {
 	public UserEntity registerNewUser(@NotNull RegistrationDto registrationDto) throws Exception {
 
 		if (userRepository.existsByEmail(registrationDto.getEmail())) {
-			throw new Exception("エラー：メール：" + registrationDto.getEmail() + " はすでに登録されました。");
+			throw new Exception("error: Email" + registrationDto.getEmail() + " had been used");
 		}
 
 		UserEntity newUser = new UserEntity();
@@ -50,7 +50,7 @@ public class UserService implements UserDetailsService {
 		UserEntity userEntity = userRepository.findByEmail(email)
 				.orElseThrow(() -> new UsernameNotFoundException(email + " not found"));
 
-		Collection<? extends GrantedAuthority> authorities = Collections.singletonList(new SimpleGrantedAuthority("ROLE_USER")); // 示例：给所有用户一个ROLE_USER权限
+		Collection<? extends GrantedAuthority> authorities = Collections.singletonList(new SimpleGrantedAuthority("ROLE_USER"));
 
 		return new User(
 				userEntity.getEmail(),
@@ -59,7 +59,7 @@ public class UserService implements UserDetailsService {
 				true,                       // accountNonExpired
 				true,                       // credentialsNonExpired
 				true,                       // accountNonLocked
-				authorities                 // 用户的权限集合
+				authorities                 // role
 		);
 	}
 }