private function getUniqueAndRequiredAssociations(ClassMetadata $meta, $entity)
 {
     $associations = array();
     foreach ($meta->getAssociationNames() as $associationName) {
         $mapping = $meta->getAssociationMapping($associationName);
         if (!empty($mapping['id']) && $meta->usesIdGenerator()) {
             // autogenerated id
             continue;
         }
         if (!($mapping['type'] & ClassMetadata::TO_ONE)) {
             // is not to one relation
             continue;
         }
         if (empty($mapping['isOwningSide'])) {
             // is not owning side
             continue;
         }
         foreach ($mapping['joinColumns'] as $joinColumn) {
             if (!empty($joinColumn['nullable']) && empty($joinColumn['unique'])) {
                 // is nullable and is not unique
                 continue;
             }
             $targetColumn = $joinColumn['referencedColumnName'];
             $targetClass = $this->em->getClassMetadata($mapping['targetEntity']);
             $newVal = $meta->getFieldValue($entity, $associationName);
             if ($newVal !== NULL) {
                 $newValId = $this->uow->getEntityIdentifier($newVal);
             }
             switch (TRUE) {
                 case $newVal === NULL:
                     $value = NULL;
                     break;
                 case $targetClass->containsForeignIdentifier:
                     $value = $newValId[$targetClass->getFieldForColumn($targetColumn)];
                     break;
                 default:
                     $value = $newValId[$targetClass->fieldNames[$targetColumn]];
                     break;
             }
             $sourceColumn = $joinColumn['name'];
             $quotedColumn = $this->quotes->getJoinColumnName($joinColumn, $meta, $this->platform);
             $associations[$sourceColumn]['value'] = $value;
             $associations[$sourceColumn]['quotedColumn'] = $quotedColumn;
             $associations[$sourceColumn]['type'] = $targetClass->getTypeOfColumn($targetColumn);
         }
     }
     return $associations;
 }