Managing state in WebSocket apps (see https://abhirockzz.wordpress.com/2017/04/15/handling-state-in-java-websocket-applications)

using_endpointconfig_configurator.txt

//custom Configurator implementation which maps (authenticated) user name to a token (sent via HTTP header)

public class TokenStore extends ServerEndpointConfig.Configurator {
    Map<String, String> userTokens;
    
    public TokenStore() {
        userTokens = new ConcurrentHashMap<>();
    }
    
    @Override
    public void modifyHandshake(ServerEndpointConfig sec, HandshakeRequest request, HandshakeResponse response) {
        String token = request.getHeaders().get("token").get(0);
        String name = request.getUserPrincipal().getName();
        userTokens.put(name, token);
    }
    
    public Map<String, String> getUserTokens(){
        return Collections.unmodifiableMap(userTokens);
    }
  
}

//the WebSocket (server) endpoint implementation which makes use of the token store

@ServerEndpoint(value = "/service/{id}",configurator = TokenStore.class)
public class BroadcastService {
    private String token;
    
    @OnOpen
    public void test(@PathParam("id") String id, EndpointConfig cfg) { //injeted config by runtime
        ServerEndpoint sCfg = (ServerEndpoint) cfg; //cast
        TokenStore store = sCfg.getConfigurator(); //get custom implementation instance
        token = cfgur.getUserTokens().get(id); //extract token and store as a member variable
    }
}