Write a java websocket client using Spring's SockJsClient

Question

I have a WebSocket server that written in Java and started without any problem. (on "ws" endpoint)

Simply, I want to develop a client in below tasks :

1. create a connection to the server
2. subscribe to defined topics (e.g "topic/public")
3. Receive from response topic
4. Send to request topic

When I used Stomp as below it works well. but I couldn't do this way when I use StandardWebSocketClient.

    //Init
    WebSocketClient client = new StandardWebSocketClient();
    WebSocketStompClient stompClient = new WebSocketStompClient(client);
    stompClient.setMessageConverter(new MappingJackson2MessageConverter());
    StompSessionHandler sessionHandler = new CustomStompSessionHandler();

    //Connect
    StompSession stompSession = stompClient.connect("ws://localhost:8080/ws", sessionHandler).get();

    //Subscribe
    stompSession.subscribe("/topic/public", sessionHandler);

    //Send Message
    stompSession.send("/app/chat.addUser", new ChatMessage(MessageType.JOIN, "New User Added"));
    stompSession.send("/app/chat.sendMessage", new ChatMessage(MessageType.CHAT, "Test Message", "Test username"));

Now I want to do this with SockJsClient. it's pretty easy to handshake and create a connection but after that, how can I subscribe to the specific topic?

    //Init
    List<Transport> transports = new ArrayList<>(2);
    transports.add(new WebSocketTransport(new StandardWebSocketClient()));
    transports.add(new RestTemplateXhrTransport());
    SockJsClient sockJsClient = new SockJsClient(transports);

    //Connect (Handshake)
    WebSocketSession webSocketSession = sockJsClient.doHandshake(new CustomWebSocketHandler(), "ws://localhost:8080/ws").get();

    //HOW CAN I SUBSCRIBE ?????

    //Send Message (To where? Which Path? Which topic)
    WebSocketMessage webSocketMessage = new TextMessage(new String("test Message").getBytes());
    webSocketSession.sendMessage(webSocketMessage);

In BRIEF: HOW CAN I SUBSCRIBE TO SPECIFIC TOPIC WHEN I USE SockJsClient?

To remind: Server was ok, and the other approach (StandardWebSocketClient) was working well.

Answer 1

If you want to implement STOMP protocol from scratch then you need to read specification and construct your SUBSCRIBE and other commands by hand in text message body.

But you can initialize the same WebSocketStompClient with configured SockJsClient as WebSocketClient constructor argument like this