ghillert/spring-integration — comment on commit 1fef979adb119d7b1b67aa0e0348bd1457a83475
File: spring-integration-core/src/main/java/org/springframework/integration/transformer/ContentEnricher.java line 160
By ghillert:

Well, the reply channel does not have to be set. However, if the reply channel is set, then the request channel becomes mandatory. That's why I have that extra if-statement in there.