Implement a stub toJSON method for the new type AInterval, we will remove this stub when visitor pattern based JSON printer is implemented.

git-svn-id: https://asterixdb.googlecode.com/svn/branches/asterix_stabilization_result_distribution@1227 eaa15691-b419-025a-1212-ee371bd00084
diff --git a/asterix-om/src/main/java/edu/uci/ics/asterix/om/base/AInterval.java b/asterix-om/src/main/java/edu/uci/ics/asterix/om/base/AInterval.java
index 66a587a..f1352f1 100644
--- a/asterix-om/src/main/java/edu/uci/ics/asterix/om/base/AInterval.java
+++ b/asterix-om/src/main/java/edu/uci/ics/asterix/om/base/AInterval.java
@@ -14,6 +14,9 @@
  */
 package edu.uci.ics.asterix.om.base;
 
+import org.json.JSONException;
+import org.json.JSONObject;
+
 import edu.uci.ics.asterix.common.exceptions.AsterixException;
 import edu.uci.ics.asterix.om.base.temporal.GregorianCalendarSystem;
 import edu.uci.ics.asterix.om.types.ATypeTag;
@@ -141,4 +144,9 @@
         return typetag;
     }
 
+    @Override
+    public JSONObject toJSON() throws JSONException {
+        // TODO(madhusudancs): Remove this method when a printer based JSON serializer is implemented.
+        return null;
+    }
 }