Flag controlling the behaviour of the container with respect to message acknowledgement. The most common usage is
to let the container handle the acknowledgements (so the listener doesn't need to know about the channel or the
message).
Set to
AcknowledgeMode#MANUAL if the listener will send the acknowledgements itself using
Channel#basicAck(long,boolean). Manual acks are consistent with either a transactional or
non-transactional channel, but if you are doing no other work on the channel at the same other than receiving a
single message then the transaction is probably unnecessary.
Set to
AcknowledgeMode#NONE to tell the broker not to expect any acknowledgements, and it will assume all
messages are acknowledged as soon as they are sent (this is "autoack" in native Rabbit broker terms). If
AcknowledgeMode#NONE then the channel cannot be transactional (so the container will fail on start up if
that flag is accidentally set).