WebSocket not being triggered from outside its class

I am using a Spring Backend with a Angular+Ionic frontend. I have created a WebSocket to trigger my frontend when a Teacher modifies a Grade in Moodle. This is irrelevant, just to give you some context.

So the problem is that mi fronted is correctly subscribed:

constructor(private apiUserService: ApiUserService) {
this.webSocket = new WebSocket('ws://localhost:8080/newGrade');
this.webSocket.onmessage = (event) => {
console.log(event.data)
}}


And it gets the first message correctly. The problem is that when I update my DB and calls the Handler to be triggered it doesn't respond. I know that the method and my plugin in Moodle is working because the DB is UPDATED:

@Autowired
private NewGradeHandler newGradeHandler;

private final ObjectMapper objectMapper = new ObjectMapper();

@PostMapping("/updateGrade")
public ResponseEntity<String> miEndpoint(@RequestBody Map<String, Object> datos) throws Exception {
try {
// Obtener los datos de la solicitud
Long userId = Long.parseLong(datos.get("userid").toString());
if (userId != -1) {
Long courseId = Long.parseLong(datos.get("courseid").toString());
int mark = Integer.parseInt(datos.get("grade").toString());
String assignmentName = datos.get("assignmentname").toString();

// Buscar el usuario y la asignatura
User student = userService.findById(userId);
Subject subject = subjectService.getSubject(courseId);

// Crear una nueva nota o actualizarla si existe
if (!subjectMarkService.existsByStudentIdAndSubjectIdAndNameMark(student, subject, assignmentName)) {
Subject_Mark newMark = new Subject_Mark(student, subject, mark, "Ordinaria", assignmentName);
subjectMarkService.save(newMark);
Subject_Mark updatedGrade = subjectMarkService.getLastSubjectMarkAdded();
sendMessageToWebSocket(updatedGrade);
} else {
updateExistingMark(student, subject, mark, assignmentName);
}

return ResponseEntity.ok("Nota creada/actualizada correctamente");
}
return ResponseEntity.ok("ok");
} catch (NumberFormatException e) {
return ResponseEntity.badRequest().body("Error al convertir los datos");
} catch (RuntimeException e) {
return ResponseEntity.badRequest().body(e.getMessage());
}
}

private void updateExistingMark(User student, Subject subject, int mark, String assignmentName) throws Exception {
Subject_Mark existingMark = subjectMarkService.findByStudentIdAndSubjectIdAndNameMark(student, subject, assignmentName).get();
existingMark.setMark(mark);
subjectMarkService.save(existingMark);
}

private void sendMessageToWebSocket(Subject_Mark grade) throws Exception {
TextMessage message = new TextMessage(objectMapper.writeValueAsString(grade));
for (WebSocketSession session : newGradeHandler.getSessions()) {
session.sendMessage(message);
}


}

My handler and its config is:

@Configuration@EnableWebSocketpublic class WebSocketConfig implements WebSocketConfigurer {
@Override
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(new NewGradeHandler(), "/newGrade").setAllowedOrigins("*");
}

@Bean
public WebSocketHandler NewGradeHandler() {
return new NewGradeHandler();
}}


And this is my Handler:

@Componentpublic class NewGradeHandler extends TextWebSocketHandler {
private final ObjectMapper objectMapper = new ObjectMapper();
private final List<WebSocketSession> sessions = new CopyOnWriteArrayList<>();
@Autowired
private SubjectMarkService subjectMarkService;

@Override
public void afterConnectionEstablished(WebSocketSession session) throws Exception {

Subject_Mark newGrade = subjectMarkService.getLastSubjectMarkAdded();

TextMessage message = new TextMessage(objectMapper.writeValueAsString(newGrade));
session.sendMessage(message);
sessions.add(session);
}

public List<WebSocketSession> getSessions() {
return sessions;
}}


I have searched some guides but the update the wbesocket from inside the class which I know it works: https://medium.com/@parthiban.rajal...ts-using-spring-boot-and-angular-b11e7363f051

I would appreciate some help.

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