spring-projects/spring-integration — pull request #1203 by garyrussell (2014-07-09 15:24:27+00:00)
Title: INT-3469 MQTT - Set Callback Before Subscribing

JIRA: https://jira.spring.io/browse/INT-3469

Previously, the callback was set immediately after
subscribing which caused a small possibility of
message loss.

Set the callback before subscribing.