Appcelerator Titanium KrollDict fails to sanitize JSONObject.NULL values

If you’re developing an Appcelerator Titanium module for Android it’s possible that you’ll run into this exception (see bottom of post for full exception trace):

!!! Unable to convert unknown Java object class 'org.json.JSONObject$1' to Js value !!!

It took me a long time to track down the cause of this error, but essentially the issue is in the JNI layer, which passes native Java objects to the Javascript layer does not know how to handle a JSONObject.NULL value. The Titanium wrapper object KrollDict attempts to convert all non-native Java objects into native ones. JSONObject becomes a simple Map, JSONArray becomes an ArrayList and so on. However, the constructor fails to account for instances of the JSONObject.NULL object, which is not a simple primitive.

An easy work around would be to ensure the JSON objects that you’re passing around never have any true JSON null values in them. You can replace them with empty strings, or simply remove the key from the object altogether. This is ultimately the fix we went with. However, a simple two-line patch should solve this issue in the core Titanium code:

From 57868ea5b822468563d4a1be2adb901cce383f11 Mon Sep 17 00:00:00 2001
From: Tristan Waddington <>
Date: Mon, 4 Jun 2012 14:24:15 -0700
Subject: [PATCH] Update the 'fromJSON' method of 'KrollDict' to map the
 'JSONObject.NULL' Object to a real Java null
 android/titanium/src/java/org/appcelerator/kroll/ |    2 ++
 1 file changed, 2 insertions(+)
diff --git a/android/titanium/src/java/org/appcelerator/kroll/ b/android/titanium/src/java/org/appcelerator/kroll/
index da29217..96017d6 100644
--- a/android/titanium/src/java/org/appcelerator/kroll/
+++ b/android/titanium/src/java/org/appcelerator/kroll/
@@ -56,6 +56,8 @@ public static Object fromJSON(Object value) {
 					values[i] = fromJSON(array.get(i));
 				return values;
+			} else if (value == JSONObject.NULL) {
+				return null;
 		} catch (JSONException e) {
 			Log.e(TAG, "Error parsing JSON", e);

I submitted a pull request to the titanium_mobile repository on GitHub, but all contributors are required to sign a Contributor License Agreement (CLA). Not a big deal, but I don’t expect to ever submit another patch to this project, so I’m not inclined to spend a day getting their dev environment bootstrapped and sign my life away for a two-line bug fix (yes, I wrote a passive-aggressive blog post instead).

Unfortunately, they don’t even seem interested in accepting the patch as a simple bug report so someone else can fix it:

If you’re trying to build a platform that’s meant to be developer focused, willful disinterest is not the best response. If you’re curious, here’s the raw patch file and the full exception: