As opposed to close(), which actively closes the session, the
onClosed method is called when the underlying connection has been
closed or disconnected.
Add HandlerProvider<T> class
Modify HandshakeHandler to accept + adapt WebSocketHandler at runtime
Modify SockJsService to accept + adapt SockJsHandler at runtime
This is useful to make sure response headers are written to the
underlying response. It is also useful in conjunction with long
running, async requests and HTTP streaming, to ensure the Servlet
response buffer is sent to the client without additional delay and
also causes an IOException to be raised if the client has gone away.
- configure SockJS handler by type (as well as by instance)
- add method to obtain SockJS handler instance via SockJsConfiguration
- detect presense of jsr-356 and use it if available
