Validate an authToken

Question

Got a websocket - see the authToken in the Cookie, in Java Spring how do you validate this authToken? I understand this authToken is passed down from the http layer to the websocket so I'm trying to validate that the websocket is being opened by our app and not by some other source.

Headers for Websocket:  
GET ws://localhost:9999/somePath/websocket HTTP/1.1  
Host: localhost:9999  
Connection: Upgrade  
Pragma: no-cache  
Cache-Control: no-cache  
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36  
Upgrade: websocket  
Origin: http://localhost  
Sec-WebSocket-Version: 13  
Accept-Encoding: gzip, deflate, br  
Accept-Language: en-US,en;q=0.9  
Cookie: authToken=elFKMk5TckR0ZUNvdnZySUJxc2ZMdz09OklEZENrRFRySkp0U0ltVFdKU1RIZVE9PQ  
Sec-WebSocket-Key: e//VDAjHSRjE810tCbIEyw==  
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits  
Sec-WebSocket-Protocol: v10.stomp, v11.stomp, v12.stomp  

I would like to validate that authToken in the HttpHandshakeInterceptor.beforeHandshake

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer
registry.addEndpoint(stompEndPoint).addInterceptors(new HttpHandshakeInterceptor()).setAllowedOrigins("*").withSockJS();

public class HttpHandshakeInterceptor implements HandshakeInterceptor
Override
public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map attributes) throws Exception {

    if (request instanceof ServletServerHttpRequest) {
        ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) request;
        HttpSession session = servletRequest.getServletRequest().getSession();
        attributes.put("sessionId", session.getId());
        // validate token logic

    }
    return true;
}