A downstream component can explicitly route a message to that channel - as long as the message has a replyChannel header - the reply-channel on the gateway simply bridges to the header channel.
This is normally not needed; if the ultimate consumer (last element in the flow) does not declare an output-channel, the framework will route the output to the header replyChannel.
It's normally only necessary to declare a reply-channel if you want to do something extra (such as logging, wire-tapping, or making the reply-channel a publish-subscribe-channel).
Many people often declare, and route to, a reply-channel when it's not needed; this doesn't hurt anything, but is not really necessary.
Gary P. Russell
Spring Integration Team
SpringSource, a division of VMware
Junior Member
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