[ONOS-4910, ONOS-4921] Framework: utils validation and defect fix

Change-Id: I821920fa8c88e64406b702c2b8736bdeaf231474
diff --git a/utils/yangutils/datamodel/src/main/java/org/onosproject/yangutils/datamodel/YangTypeDef.java b/utils/yangutils/datamodel/src/main/java/org/onosproject/yangutils/datamodel/YangTypeDef.java
index 6fd95e0..085a5c8 100644
--- a/utils/yangutils/datamodel/src/main/java/org/onosproject/yangutils/datamodel/YangTypeDef.java
+++ b/utils/yangutils/datamodel/src/main/java/org/onosproject/yangutils/datamodel/YangTypeDef.java
@@ -251,7 +251,9 @@
      */
     @Override
     public void validateDataOnExit() throws DataModelException {
-        // TODO auto-generated method stub, to be implemented by parser
+        if (defaultValueInString != null && !defaultValueInString.isEmpty() && getTypeDefBaseType() != null) {
+            getTypeDefBaseType().isValidValue(defaultValueInString);
+        }
     }
 
     /**