A default {@link org.springframework.web.socket.server.HandshakeHandler} implementation.Performs initial validation of the WebSocket handshake request -- possibly rejecting it through the appropriate HTTP status code -- while also allowing sub-classes to override various parts of the negotiation process (e.g. origin validation, sub-protocol negotiation, extensions negotiation, etc).
If the negotiation succeeds, the actual upgrade is delegated to a server-specific {@link org.springframework.web.socket.server.RequestUpgradeStrategy}, which will update the response as necessary and initialize the WebSocket. Currently supported servers are Tomcat 7 and 8, Jetty 9, and GlassFish 4.
@author Rossen Stoyanchev
@since 4.0