javax.websocket.DeploymentException

Question

I am using Intellij IDEA. And i am trying to coding java websocket. But i have an error. How can i fix this bug.?

public class Main {
    public static void main(String[] args) throws NTLMException {
        runServer();
    }

    public static void runServer() throws NTLMException {
        Server s = new Server("localhost", 8000, "/ws", WsServer.class);
        try {
            s.start();
            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Please press a key to stop the server.");
            reader.readLine();
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            s.stop();
        }


@ServerEndpoint("/websocket")
public class WsServer {

    private Logger logger = Logger.getLogger(this.getClass().getName());

    @OnOpen
    public void onOpen(Session session) {
        logger.info("Connected.:" + session.getId());
    }



    @OnMessage
    public String onMessage(String message, Session session) {
        switch (message) {
            case "quit":
                try {
                    session.close(new CloseReason(CloseCodes.NORMAL_CLOSURE, "END"));
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
                break;
        }
        return message;
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        logger.info(String.format("Session %s closed because of %s", session.getId(), closeReason));
    }
}

Exception in thread "main" java.lang.NoClassDefFoundError: > javax/websocket/DeploymentException at > ws.Main.runServer(Main.java:14) at ws.Main.main(Main.java:10) Caused > by: java.lang.ClassNotFoundException: > javax.websocket.DeploymentException at > java.net.URLClassLoader.findClass(URLClassLoader.java:382) at > java.lang.ClassLoader.loadClass(ClassLoader.java:418) at > sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355) at > java.lang.ClassLoader.loadClass(ClassLoader.java:351) ... 2 more