From 684c18a6b831e7abe200aafa7475a007944239ed Mon Sep 17 00:00:00 2001
From: Pierre Villard <pierre.villard.fr@gmail.com>
Date: Wed, 11 Jan 2017 02:12:07 +0100
Subject: [PATCH] NIFI-1962 - Fixed NPE in toDate() EL function

---
 .../language/evaluation/functions/NumberToDateEvaluator.java   | 2 +-
 .../apache/nifi/attribute/expression/language/TestQuery.java   | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/evaluation/functions/NumberToDateEvaluator.java b/nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/evaluation/functions/NumberToDateEvaluator.java
index 6867202ad0fc..c4b14bb6460c 100644
--- a/nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/evaluation/functions/NumberToDateEvaluator.java
+++ b/nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/evaluation/functions/NumberToDateEvaluator.java
@@ -37,7 +37,7 @@ public QueryResult<Date> evaluate(final Map<String, String> attributes) {
         final QueryResult<Long> result = subject.evaluate(attributes);
         final Long value = result.getValue();
         if (value == null) {
-            return null;
+            return new DateQueryResult(null);
         }
 
         return new DateQueryResult(new Date(value));
diff --git a/nifi-commons/nifi-expression-language/src/test/java/org/apache/nifi/attribute/expression/language/TestQuery.java b/nifi-commons/nifi-expression-language/src/test/java/org/apache/nifi/attribute/expression/language/TestQuery.java
index 03de38f98734..5946aa5b3190 100644
--- a/nifi-commons/nifi-expression-language/src/test/java/org/apache/nifi/attribute/expression/language/TestQuery.java
+++ b/nifi-commons/nifi-expression-language/src/test/java/org/apache/nifi/attribute/expression/language/TestQuery.java
@@ -898,6 +898,9 @@ public void testDate() {
 
         verifyEquals("${entryDate:toNumber():toDate():format('yyyy')}", attributes, String.valueOf(year));
 
+        // test for not existing attribute (NIFI-1962)
+        assertEquals("", Query.evaluateExpressions("${notExistingAtt:toDate()}", attributes, null));
+
         attributes.clear();
         attributes.put("month", "3");
         attributes.put("day", "4");