Websockets with Spring Boot

WebSockets is an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. WebSockets use TCP for communcation.

In this project, a thin layer on top of the websocket protocol is used called STOMP (Simple Text- Orientated Messaging Protocol). This defines a common protocol for every client who wants to communicate with any STOMP message broker. STOMP with spring uses channels to recieve and broadcast messages to clients. A client has to subscribe to a channel to get messages from the broker.

Using Websockets in spring

Backend

  1. Add needed dependencies to gradle.build
compile('org.springframework:spring-messaging')
compile('org.springframework.boot:spring-boot-starter-websocket')

//JavaScript dependencies
compile('org.webjars:sockjs-client:1.1.1')
compile('org.webjars:stomp-websocket:2.3.3')

  1. Create socket config

    • Create WebSocketConfig which extends from AbstractWebSocketMessageBrokerConfigurer
    • register Stomp endpoint, define here that this endpoint will use SockJS (.withSockJS())

  2. Send messages from broker to clients

    • inject SimpMessagingTemplate
    • send message with template.convertAndSend("your/channel", object)

  3. Receive messages from clients to broker

    • Create controller class
    • Annotate receiving methods with @MessageMapping("/your/channel") annotation

Frontend

  1. Add JS dependencies

    <script src="/webjars/sockjs-client/1.1.1/sockjs.js"></script>
<script src="/webjars/stomp-websocket/2.3.3/stomp.js"></script>

  2. Create SockJS and configure Stomp

    var socket = new SockJS('your-configured-endpoint-in-WebSocketConfig');
stompClient = Stomp.over(socket);

  3. Subscribe to a channel

    stompClient.subscribe('/channel/to/subscribe/', callback)

  4. Send messages to broker

    stompClient.send("/channel/to/send", headerObj, bodyObj);