I am using the Class - PrintingListener from stomp.py, and it has the method: on_before_message.
I am not sure why this method is called. I cannot understand the definition. Could someone clarify the use of this method and when it is called?
According to the stomp.py documentation, the PrintingListener "just prints all interactions between the client and server." The on_before_message is one of the methods defined by stomp.py therefore the PrintingListener invokes it.
The stomp.py API documentation says this about on_before_message:
Called by the STOMP connection before a message is returned to the client app. Returns a tuple containing the headers and body (so that implementing listeners can pre-process the content).
Parameters:
- headers (dict) – the message headers
- body – the message body
As stated here, on_before_message is invoked "so that implementing listeners can pre-process the content." If you don't need to pre-process the content of the message (i.e. the headers or the body) then you can ignore this method.
As the name indicates on_before_message is invoked immediately before on_message.