RED-6310: Moved code to create user-preferences to a separate class so that the calling code can handle a persistence exception

persistence-service-v1/persistence-service-processor-v1/src/main/java/com/iqser/red/service/persistence/management/v1/processor/service/persistence/NotificationPreferencesPersistenceService.java

@@ -10,6 +10,8 @@ import java.util.stream.Collectors;
 import javax.transaction.Transactional;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.dao.DataIntegrityViolationException;
+import org.springframework.stereotype.Component;
 import org.springframework.stereotype.Service;
 
 import com.iqser.red.service.persistence.management.v1.processor.entity.notification.NotificationPreferencesEntity;
@@ -18,15 +20,20 @@ import com.iqser.red.service.persistence.management.v1.processor.service.persist
 import com.iqser.red.service.persistence.service.v1.api.model.notification.NotificationPreferences;
 import com.iqser.red.service.persistence.service.v1.api.model.notification.NotificationType;
 
+import lombok.AccessLevel;
 import lombok.RequiredArgsConstructor;
+import lombok.experimental.FieldDefaults;
 
 @Service
 @RequiredArgsConstructor
+@FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE)
 public class NotificationPreferencesPersistenceService {
 
-    private final NotificationPreferencesRepository notificationPreferencesRepository;
+    NotificationPreferencesRepository notificationPreferencesRepository;
 
-    private final NotificationRepository notificationRepository;
+    NonThreadSafeNotificationPreferencesRepositoryWrapper notificationPreferencesRepositoryWrapper;
+
+    NotificationRepository notificationRepository;
 
 
     @Transactional
@@ -64,18 +71,17 @@ public class NotificationPreferencesPersistenceService {
     }
 
 
-    @Transactional
+    // This method intentionally does not have a @Transactional annotation, since it needs to handle an underlying transaction exception.
     public NotificationPreferencesEntity getOrCreateNotificationPreferences(String userId) {
 
-        return notificationPreferencesRepository.findByUserId(userId).orElseGet(() -> {
-
-            var notificationPreference = new NotificationPreferencesEntity();
-            notificationPreference.setUserId(userId);
-            notificationPreference.setEmailNotificationsEnabled(false);
-            notificationPreference.setInAppNotificationsEnabled(true);
-            notificationPreference.setInAppNotifications(Arrays.stream(NotificationType.values()).map(Enum::name).collect(Collectors.toList()));
-            return notificationPreferencesRepository.save(notificationPreference);
-        });
+        try {
+            // The method called here will fail if it is called concurrently (more than 1 thread), since it will always try to create
+            // the desired entity.  But the exception only means, that the entity has been created by another thread.
+            // In that case we can just fetch the data from the db.
+            return notificationPreferencesRepositoryWrapper.getOrCreateNotificationPreferences(userId);
+        } catch (DataIntegrityViolationException ex) {
+            return notificationPreferencesRepository.getByUserId(userId);
+        }
     }
 
 
@@ -91,4 +97,29 @@ public class NotificationPreferencesPersistenceService {
         return notificationPreferencesRepository.findAll();
     }
 
+
+    @Component
+    @RequiredArgsConstructor
+    @FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE)
+    private static class NonThreadSafeNotificationPreferencesRepositoryWrapper {
+
+        NotificationPreferencesRepository notificationPreferencesRepository;
+
+
+        @Transactional(Transactional.TxType.REQUIRES_NEW)
+        public NotificationPreferencesEntity getOrCreateNotificationPreferences(String userId) {
+
+            return notificationPreferencesRepository.findByUserId(userId).orElseGet(() -> {
+
+                var notificationPreference = new NotificationPreferencesEntity();
+                notificationPreference.setUserId(userId);
+                notificationPreference.setEmailNotificationsEnabled(false);
+                notificationPreference.setInAppNotificationsEnabled(true);
+                notificationPreference.setInAppNotifications(Arrays.stream(NotificationType.values()).map(Enum::name).collect(Collectors.toList()));
+                return notificationPreferencesRepository.save(notificationPreference);
+            });
+        }
+
+    }
+
 }

persistence-service-v1/persistence-service-processor-v1/src/main/java/com/iqser/red/service/persistence/management/v1/processor/service/persistence/repository/NotificationPreferencesRepository.java

@@ -11,6 +11,9 @@ public interface NotificationPreferencesRepository extends JpaRepository<Notific
     Optional<NotificationPreferencesEntity> findByUserId(String userId);
 
 
+    NotificationPreferencesEntity getByUserId(String userId);
+
+
     void deleteByUserId(String userId);
 
 }