I am not receiving WebSocket messages (SimpMessagingTemplate) - spring

Question

I am not able to get my WS working. I wrote this test and it is still failing when I use simpMessagingTemplate but when I use stompSession.send it works. Could anyone help me where I am making mistake?
The problem is NOT in the test PROBABLY, I am not able to make simpMessagingTemplate working in any service.
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
#ExtendWith(MockitoExtension.class)
public class WebSocketSpec {
#LocalServerPort
private Integer port;
#Autowired
private SimpMessagingTemplate simpMessagingTemplate;
private WebSocketStompClient webSocketStompClient;
#BeforeEach
public void initialize(){
webSocketStompClient = new WebSocketStompClient(new SockJsClient(List.of(new WebSocketTransport(new StandardWebSocketClient()))));
}
#Test #DisplayName("test subscription to /topic/plcs/connection-status")
void testSubscriptionToPlcConnectionEndpoint() throws Exception{
CountDownLatch latch = new CountDownLatch(1);
webSocketStompClient.setMessageConverter(new MappingJackson2MessageConverter());
StompSession stompSession = webSocketStompClient.connect("ws://localhost:" + port+"/api/ws", new StompSessionHandlerAdapter() {
}).get(1, TimeUnit.SECONDS);
stompSession.subscribe("/topic/plcs/connection-status", new StompFrameHandler() {
#Override
public Type getPayloadType(StompHeaders stompHeaders) {
return String.class;
}
#Override
public void handleFrame(StompHeaders stompHeaders, Object o) {
latch.countDown();
System.out.println("RECEIVED: "+o);
}
});
//stompSession.send("/topic/plcs/connection-status", "SENT FROM TEST!!!");
simpMessagingTemplate.convertAndSend("/topic/plcs/connection-status", "SENT FROM TEST!!!");
if (!latch.await(5, TimeUnit.SECONDS)){
fail("Message not received");
}
}
}
My configuration for WS looks like this:
#Configuration
#EnableWebSocketMessageBroker
public class WebSocketConfiguration implements WebSocketMessageBrokerConfigurer {
#Override
public void configureMessageBroker(MessageBrokerRegistry config) {
config.enableSimpleBroker("/queue", "/topic");
config.setApplicationDestinationPrefixes("/app");
}
#Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry.addEndpoint("/ws").withSockJS();
}
}

Answer 1

So, there are actually two problems ...
first is that you are using wrong messageConvertor (new MappingJackson2MessageConverter() instead of new StringMessageConverter())
the simpMessagingTemplate.convertAndSend("/topic/plcs/connection-status", "SENT FROM TEST!!!"); is fired before the client is subscribed, I have just tried to put there some delay before it with Thread.sleep(500); and it worked.