diff -r e63ac93fdbde -r 45378793512a Entity/DocumentRepository.php
--- a/Entity/DocumentRepository.php	Mon Oct 17 17:17:14 2011 +0200
+++ b/Entity/DocumentRepository.php	Tue Oct 18 10:32:30 2011 +0200
@@ -13,16 +13,20 @@
  */
 class DocumentRepository extends EntityRepository
 {
+    function findOneByExternalId($external_id)
+    {
+        return $this->findOneBy(array("externalId" => strval($external_id)));
+    }
     
     function writeDocument(DocumentInterface $document)
     {
         # get document from id
-        $baseDocument = $this->findOneBy(array("externalId" => $document->getId()));
+        $baseDocument = $this->findOneByExternalId($document->getId());
     
         if(is_null($baseDocument))
         {
             $baseDocument = new Document();
-            $baseDocument->setExternalId($document->getId());
+            $baseDocument->setExternalId(strval($document->getId()));
         }
         $baseDocument->setDescription($document->getDescription());
         $baseDocument->setTitle($document->getTitle());
@@ -35,8 +39,9 @@
     
     function removeDocument(DocumentInterface $document)
     {
-        $baseDocument = $this->findOneBy(array("externalId" => $document->getId()));
-        if(!is_null($baseDocument)) {
+        $baseDocument = $this->findOneByExternalId($document->getId());
+        if(!is_null($baseDocument))
+        {
             $this->getEntityManager()->remove($baseDocument);
         }
     }