Where “user” comes from in convertAndSendToUser works in SockJS+Spring Websocket?

Question

I would like to understand how convertAndSendToUser works in Spring SockJS+Websocket framework.

In client, we would connect as

stompClient.connect(lo         


        

Answer 1

I did not do any specific configuration and I can just do this:

@MessageMapping('/hello')
protected void hello(Principal principal, Map message) {
    String username = principal.getName();
}