curl -H "Content-Type: application/json" -X POST -d "{\"time\": \"2019-12-27T09:50:02.000+0000\", \"unread\": true, \"message\": \"asd\", \"from\": \"John\"}" localhost:8080/api/save

{"timestamp":"2020-01-05T04:36:33.192+0000","status":500,"error":"Internal Server Error","message":"No message available","trace":"java.lang.NullPointerException\r\n\tat org.vaadin.marcus.spring.service.impl.MessageServiceImpl.add(MessageServiceImpl.java:45)\r\n\tat org.vaadin.marcus.spring.service.impl.MessageServiceImpl$$FastClassBySpringCGLIB$$2d73a7c.invoke(<generated>)\r\n\tat org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)\r\n\tat org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746)\r\n\tat org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)\r\n\tat org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:294)\r\n\tat org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98)\r\n\tat org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)\r\n\tat org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept

@Service
@Transactional
public class MessageServiceImpl implements MessageService {
    private final MessageRepository repository;
    private final PageRequest lastRequest;

    private List<Long> chekedMessages = new ArrayList<>();


    @Autowired
    public MessageServiceImpl(MessageRepository repository) {
        this.repository = repository;
        lastRequest = new PageRequest(0, 10, Sort.Direction.DESC, "id");
    }

    @Override
    public MessageStatus add(@RequestBody  Message message) {
        MessageStatus status = null;
        try {
            repository.save(message);
            status.setMessage("Сообщение успешно сохранено");
        }
        catch (Exception e) {
            status.setMessage("Во время сохранения сообщения произошла ошибка - " + e);
        }
        return status;
    }

    @Override
    public List<Message> getAllMessages() {
        return repository.findAll();
    }

    @Override
    public List<Message> getLast() {
        List<Message> result = repository.findAll(lastRequest).getContent();

        return result.stream()
                .sorted(Comparator.comparingLong(Message::getId))
                .collect(Collectors.toList());
    }

    @Override
    public List<Message> getUnreadById(long id) {
        return repository.getUnreadById(id);
    }

    

    @Override
    public String getUnreadMessages() {
        List<Message> out = new ArrayList<>();
        List<Message> unchekedMessages = repository.findAll();
        for (Message message: unchekedMessages) {
            if (!chekedMessages.contains(message.getId())) {
                chekedMessages.add(message.getId());
                out.add(message);
            }
        }
        return new Gson().toJson(out);
    }

    @Override
    public void updateMessage(long id, Message message) {
        if (repository.findById(id).isPresent()) {
            message.setId(id);
            repository.save(message);
        }
    }
}

public class RestController {

    @Autowired
    TimerTask timerTask;

    @Resource
    private final MessageService messageService;

    public RestController(MessageService messageService) {
        this.messageService = messageService;
    }

    @PostMapping("/api/save")
    public MessageStatus saveMessage(@RequestBody Message chatMessage) {
        return messageService.add(chatMessage);
    }

    @GetMapping("/api/last")
    public String getLasts() {
        return new Gson().toJson(messageService.getLast());
    }

    @GetMapping("/api/unread")
    public void getUnreadMessages() {
        
        timerTask.run();
    }

    @GetMapping("/api/unread/{id}")
    public List<Message> getUnreadById(@PathVariable ("id") long id) {
        return messageService.getUnreadById(id);
    }