Websocket • 2 min read

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer{

    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws")
                .setAllowedOrigins("https://nighthawkcoders.github.io", "https://cj-backend.stu.nighthawkcodingsociety.com","http://localhost:4000", "https://toby-leeder.github.io", "https://classroomjukebox.com/")
                .withSockJS();
    }


    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry){
        registry.setApplicationDestinationPrefixes("/app");
        registry.enableSimpleBroker("/topic");
    }
}

Creating the SockJS endpoint. Also creates a the configureMessageBroker method, which is used later. /app is how you connect pretty much, and /topic is the endpoint used for messages.

@Component
@RequiredArgsConstructor
@Slf4j
public class WebSocketEventListener {
    
    private final SimpMessageSendingOperations messageTemplate;

    @EventListener
    public void handleWebSocletDisconnectListener(SessionDisconnectEvent event){
        StompHeaderAccessor headerAccessor = StompHeaderAccessor.wrap(event.getMessage());
        String username = (String) headerAccessor.getSessionAttributes().get("username");
        if (username != null){
            log.info("User disconnected: {}", username);
            var chatMessage = ChatMessage.builder()
                .type(MessageType.LEAVE)
                .sender(username)
                .build();
            messageTemplate.convertAndSend("/topic/public", chatMessage);
        }
    }
}

@Controller
public class ChatController {
    
    @MessageMapping("/chat.sendMessage")
    @SendTo("/topic/public")
    public ChatMessage sendMessage(@Payload ChatMessage chatMessage){
        return chatMessage;
    }

    @MessageMapping("/chat.addUser")
    @SendTo("/topic/public")
    public ChatMessage addUser(@Payload ChatMessage chatMessage, SimpMessageHeaderAccessor headerAccessor){
        // Add username in web socket session
        headerAccessor.getSessionAttributes().put("username", chatMessage.getSender());
        return chatMessage;
    }
}