SLING-2944 : Replace administrative login by service-based login

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1523560 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/sling/jcr/base/AbstractSlingRepository.java b/src/main/java/org/apache/sling/jcr/base/AbstractSlingRepository.java
index e890079..5768eeb 100644
--- a/src/main/java/org/apache/sling/jcr/base/AbstractSlingRepository.java
+++ b/src/main/java/org/apache/sling/jcr/base/AbstractSlingRepository.java
@@ -322,6 +322,10 @@
     final Session loginService(final Bundle usingBundle, final String subServiceName, final String workspace)
             throws LoginException, RepositoryException {
         final String userName = this.serviceUserMapper.getServiceUserID(usingBundle, subServiceName);
+        if (userName == null) {
+            throw new LoginException("Cannot derive user name for bundle "
+                + usingBundle + " and sub service " + subServiceName);
+        }
         final SimpleCredentials creds = new SimpleCredentials(userName, new char[0]);
 
         Session admin = null;