@Service public class InvoiceService { @Autowired private UserRepository userRepository; @Autowired private InvoiceRepository invoiceRepository; @Transactional public void createInvoice(Long invoiceId, Double totalAmount, Long userId) { User user = userRepository.findOne(userId); Invoice invoice = new Invoice(); invoice.setUser(user); invoice.setId(invoiceId); invoice.setTotalAmount(totalAmount); invoiceRepository.save(invoice); } }