Spring Jpa / Hibernate - Deadlock found when trying to get lock; try restarting transaction

Question

I got a deadlock problem with mysql and an application that I am developing. The application, based on spring boot, integration and jpa, has different threads and all of them can access this service:

   @Override
    @Transactional()
    public List<TwitterUser> storeTwitterUsers(List<TwitterUser> twitterUsers)
    {
        logger.debug("Store list of users, total: " + twitterUsers.size());

        List<TwitterUser> savedUsers = new ArrayList<>();

        for ( TwitterUser twitterUser : twitterUsers ) {

            TwitterUser user  = getTwitterUserById(twitterUser.getTwitterId());

            if ( user != null ) {
                twitterUser.setId(user.getId());
                user = entityManager.merge(twitterUser);

            } else {
                //HERE THE EXCEPTION IS THROWN
                entityManager.persist(twitterUser);
                user = twitterUser;
            }

            entityManager.flush();

            savedUsers.add(user);
        }

        return savedUsers;
    }

    @Override
    @Transactional(readOnly = true)
    public TwitterUser getTwitterUserById(Long id)
    {
        Query query = entityManager.createQuery("from TwitterUser u where u.twitterId=:id");
        query.setParameter("id", id);

        TwitterUser twitterUser = null;

        //Throw Exception NoResultException
        try {
            twitterUser = (TwitterUser)query.getSingleResult();
        } catch (NoResultException e) {
            //no result found
        }

        return twitterUser;
    }

When more than one thread is within the method storeTwitterUsers, mysql throw this error:

Deadlock found when trying to get lock; try restarting transaction

This is the full stack track of the error:

http://pastebin.com/nZEvykux

I already read those two questions:

How to avoid mysql 'Deadlock found when trying to get lock; try restarting transaction'

Getting "Deadlock found when trying to get lock; try restarting transaction"

but my problem seems slightly different because I got the exception when almost any thread tries to persist the object.

Is there a clean and easy way to resolve the problem without implementing a low level code check? Can Spring JPA automatically manage the deadlock situation?

Any help is really appreciated, I am struggling with that error!