Paasing authentication header to javax.websocket ClientEndpoint - spring-boot

Question

I am trying to connect to websocket server endpoint using below code but I am not able to resolve container.connectToServer(this, cec, uri); this. This method is not able to take my class as Endpoint class. It's a spring boot project. If I don't pass config then it accepts but then it fails to connect to server and return 401. I have tried many online links but failed to resolve this issue. Need help in how to fix it.
#ClientEndpoint
public class TestClassEndpoint {
private Session userSession = null;
public TestClassEndpoint(URI uri) {
try {
WebSocketContainer container = ContainerProvider.getWebSocketContainer();
ClientEndpointConfig cec = ClientEndpointConfig.Builder
.create().configurator(new ClientEndpointConfig.Configurator() {
public void beforeRequest(Map<String, List<String>> headers) {
System.out.println("Setting user cookie in beforeRequest ...");
headers.put("Authorization", Arrays.asList("Basic base64encodedString"));
}
}).build();
container.connectToServer(this, cec, uri);
} catch (Exception e) {
e.printStackTrace();
}
}
#OnOpen
public void onOpen(Session session) {
this.userSession = session;
System.out.println("New connection established");
}
#OnMessage
public void onMessage(String message, Session session) {
System.out.println(message);
}
#OnClose
public void onClose(Session userSession, CloseReason reason) {
this.userSession = null;
System.out.println("connection closed");
}
#OnError
public void onError(Throwable t) {
}
private void sendMessage(ByteBuffer buffer) {
this.userSession.getAsyncRemote().sendBinary(buffer);
}
}
Main class
#SpringBootApplication
public class MainApplication implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(TwilioPocApplication.class, args);
}
#Override
public void run(String... args) throws Exception {
URI uri = UriComponentsBuilder.fromUriString("server_url").build().toUri();
new TestClassEndpoint(uri);
}
}