From 8deec9569c2741c2fc5a78e375765dfb93586f49 Mon Sep 17 00:00:00 2001
From: Rossen Stoyanchev <rstoyanchev@pivotal.io>
Date: Mon, 22 May 2017 16:08:22 -0400
Subject: [PATCH] Protect against NPE in DefaultSubscriptionRegistry

Follow-up fix on the recent commit:
https://github.com/spring-projects/spring-framework/commit/4fc41e

Issue: SPR-15543
---
 .../messaging/simp/broker/DefaultSubscriptionRegistry.java     | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java b/spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java
index 8f95bffc7e8..5a55128501d 100644
--- a/spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java
+++ b/spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java
@@ -293,7 +293,8 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 					if (getPathMatcher().match(destination, cachedDestination)) {
 						LinkedMultiValueMap<String, String> subs = entry.getValue();
 						// Subscription id's may also be populated via getSubscriptions()
-						if (!subs.containsKey(sessionId) || !subs.get(sessionId).contains(subsId)) {
+						List<String> subsForSession = subs.get(sessionId);
+						if (subsForSession == null || !subsForSession.contains(subsId)) {
 							subs.add(sessionId, subsId);
 							this.accessCache.put(cachedDestination, subs.deepCopy());
 						}