Add check if username is already taken

Author: Konstantin Pankratov

server/src/main/java/com/studybuddies/server/persistance/UserRepository.java

@@ -8,5 +8,6 @@
 public interface UserRepository extends CrudRepository<UserEntity, UUID> {
   Optional<UserEntity> findById(UUID id);
   boolean existsById(UUID id);
+  boolean existsByUsername(String username);
   void deleteById(UUID id);
 }

server/src/main/java/com/studybuddies/server/services/exceptions/UsernameAlreadyTakenException.java

@@ -0,0 +1,8 @@
+package com.studybuddies.server.services.exceptions;
+
+public class UsernameAlreadyTakenException extends StudyBuddiesException {
+
+  public UsernameAlreadyTakenException(String message) {
+    super(message);
+  }
+}

server/src/main/java/com/studybuddies/server/services/user/UserService.java

@@ -4,6 +4,7 @@
 import com.studybuddies.server.persistance.UserRepository;
 import com.studybuddies.server.services.UUIDService;
 import com.studybuddies.server.services.exceptions.UserAccountSetupNotFinished;
+import com.studybuddies.server.services.exceptions.UsernameAlreadyTakenException;
 import com.studybuddies.server.services.interfaces.CRUDService;
 import com.studybuddies.server.web.dto.AccountChangeRequest;
 import com.studybuddies.server.web.dto.UserAccountSetupRequest;
@@ -41,6 +42,10 @@ public void create(UserAccountSetupRequest userAccountSetupRequest, String userU
       throw new AccountSetupAlreadyFinished("");
     }
 
+    if(userRepository.existsByUsername(userAccountSetupRequest.username)) {
+      throw new UsernameAlreadyTakenException("");
+    }
+
     UserEntity user = userMapper.toUserEntity(userAccountSetupRequest);
     user.setUuid(uuid);
     userRepository.save(user);

server/src/main/java/com/studybuddies/server/web/GlobalExceptionHandler.java

@@ -4,6 +4,7 @@
 import com.studybuddies.server.services.exceptions.MeetingNotFoundException;
 import com.studybuddies.server.services.exceptions.MergeFailedException;
 import com.studybuddies.server.services.exceptions.UserAccountSetupNotFinished;
+import com.studybuddies.server.services.exceptions.UsernameAlreadyTakenException;
 import com.studybuddies.server.web.mapper.exceptions.AccountSetupAlreadyFinished;
 import com.studybuddies.server.web.mapper.exceptions.DateFormatException;
 import com.studybuddies.server.web.mapper.exceptions.EndDateAfterStartDateException;
@@ -54,4 +55,9 @@ protected ResponseEntity<?> handleInvalidUUIDException() {
   protected ResponseEntity<?> handleMergeFailedException() {
     return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Updating failed. Please create an issue on GitHub");
   }
+
+  @ExceptionHandler(UsernameAlreadyTakenException.class)
+  protected ResponseEntity<?> handleUsernameAlreadyTakenException() {
+    return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("Username already taken");
+  }
 }