From 50cc5004292015ac325f3ffb761e2265b588ee1e Mon Sep 17 00:00:00 2001
From: Mark Fisher <markfisher@vmware.com>
Date: Thu, 3 Nov 2011 10:19:12 -0400
Subject: [PATCH] fixed atomicity

---
 .../integration/store/SimpleMessageStore.java            | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java b/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
index c032c58e3f..816db96d6e 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
@@ -169,10 +169,13 @@ public class SimpleMessageStore extends AbstractMessageGroupStore implements Mes
 	}
 	
 	private SimpleMessageGroup getMessageGroupInternal(Object groupId) {
-		if (!groupIdToMessageGroup.containsKey(groupId)) {
-			groupIdToMessageGroup.putIfAbsent(groupId, new SimpleMessageGroup(groupId));
+		SimpleMessageGroup group = this.groupIdToMessageGroup.get(groupId);
+		if (group == null) {
+			SimpleMessageGroup newGroup = new SimpleMessageGroup(groupId);
+			SimpleMessageGroup previousGroup = this.groupIdToMessageGroup.putIfAbsent(groupId, newGroup);
+			group = (previousGroup == null) ? newGroup : previousGroup;
 		}
-		return groupIdToMessageGroup.get(groupId);
+		return group;
 	}
 
 }