How to pass parameter/attribute to JSR-356 WebSocket client (@ClientEndpoint)?

Question

I want to add some additional attributes to container-instantiated WebSocket client endpoint for grouping/statistics. I created a client WebSocket endpoint with JSR-356:

Session session = container.connectToServer( MyClientEndpoint.class , uri );

I want to pass some object to Session or MyClientEndpoint instance:

@ClientEndpoint
public class MyClientEndpoint {

    @OnOpen
    public void onWebSocketConnect( Session sess ) {
       ...i need my param here...
    } 

    ... @OnMessage, @OnClose, @OnError handlers...
}

Because MyClientEndpoint instance is instantiated by container (in my example - Jetty), I cannot just pass argument in constructor. Also I cannot set my param in Session user properties:

Session session = container.connectToServer( ClientSocket.class , uri ); session.getUserProperties().put( "group", this);

because I don't have my property in @OnOpen handler and also I have no guarantee that my "group" property will be set before any @OnMessage call.

How to connect to JSR-356 WebSocket in a way that will allow me to use additional objects in @ClientEndpoint object instantiated by container?

Answer 1

Actually, we are not forced to container-instantiation of @ClientEndpoint instances. We can pass our custom instance:

ClientSocket socket = new ClientSocket( ANY PARAMS WE WANT );
Session session = container.connectToServer( socket , uri );