Direct Exchange to send any message will be forwarded to RouteKey specified Queue.
1. General use rabbitMQ comes Exchange: "" (the name is an empty string Exchange, hereinafter referred to as default Exchange).
The binding does not require any Exchange (Binding) 2. Operation in this mode
Requires a "RouteKey" 3. messaging, can be simply understood as the name of the queue to be sent.
4. If the queue name does not exist RouteKey vhost specified, then the message will be discarded.