Added resource and annotation services.
diff --git a/src/main/java/de/ids_mannheim/korap/utils/JsonUtils.java b/src/main/java/de/ids_mannheim/korap/utils/JsonUtils.java
index 84537a5..835106b 100644
--- a/src/main/java/de/ids_mannheim/korap/utils/JsonUtils.java
+++ b/src/main/java/de/ids_mannheim/korap/utils/JsonUtils.java
@@ -29,7 +29,7 @@
             return mapper.writeValueAsString(values);
         }
         catch (JsonProcessingException e) {
-            return "";
+            return e.getMessage();
         }
     }