Quarkus RESTEasy and update with Transaction

ProjectService.java

  
@ApplicationScoped
public class ProjectService {

    @Inject
    UserTransaction transaction;

    private static Logger logger = LoggerFactory.getLogger(ProjectService.class);

    @Inject
    ClientService clientService;

    @Inject
    UserService userService;
    
    public Optional<Long> update(Long id, ProjectRequest request, AuthenticationContext ctx)  {
        logger.debug("Modify project for for id={} with {}, {}", id, request, ctx);
        try {
            transaction.begin(); // See https://quarkus.io/guides/transaction API Approach
            final var updatedProject = findById(id, ctx)
                    .stream()
                    .map(project -> request.unbind(project, clientService::findById, userService::findById, ctx))
                    .peek(project -> project.users
                            .stream()
                            .filter(request::notContains)
                            .forEach(PanacheEntityBase::delete))
                    .map(project -> project.id)
                    .findFirst();
            transaction.commit();
            return updatedProject;
        } catch (Throwable e) {
            // There are many various exceptions, we catch Throwable but this is arguable.
            logger.warn("Could not update a Project due to an exception {}", e.getMessage());
            try {
                if (transaction.getStatus() != Status.STATUS_MARKED_ROLLBACK && transaction.getStatus() != Status.STATUS_NO_TRANSACTION) {
                    transaction.rollback();
                }
            } catch (SystemException ex) {
                logger.error("Tried to rollback in ProjectService but failed",ex);
            }
            throw new UpdateResourceException("Cannot update a Project, invalid projectRequest");
        }
    }
    
    // .... 
    
    
}

This is an extract from a project we're working on.

The ProjectService is injected into a REST ProjectResource. The transactional annotation is not used, since we're trying to trigger a validation on update. Due to Panache, we cannot use a persistAndFlush() here. Thus the only solution I found was to use the UserTransaction as explained in Quarkus documentation
https://quarkus.io/guides/transaction

The unbind method is a custom BiFunction method, created by @Fabszn, that unwrapp a ProjectRequest, try to lookup and to resolve the client and the user that are required to update a Project.