Called by TransactionTemplate locking func works, but with @Transactional it fails?

[cogpp]

Hello,

I am seeing different behavior with regard to locks with @Transactional and TransactionTemplate, although I assumed they would be the same. I have a need to issue numbers which are never duplicated. The main transaction which requires one of these numbers takes a while to complete so it calls a function which demands a new transaction, gets a pessimistic locak, issues the number then returns like this:-

@PersistenceContext
private EntityManager entityManager;
@Transactional(propagation = Propagation.REQUIRES_NEW,readOnly = false)
public int issueSequenceNumber(int id) {
	SequentialObject sequentialObject=entityManager.find(SequentialObject.class,id, LockModeType.PESSIMISTIC_FORCE_INCREMENT);
	int sequntialNumber=sequentialObject.getCurrentNumber();
	sequntialNumber++;
	sequentialObject.setCurrentNumber(sequntialNumber);
	entityManager.persist(sequentialObject);
	return sequntialNumber;
}

A method that calls this had transaction template and looked like this:-

    public void callsIssueSequenceNumber() {
        PlatformTransactionManager platformTransactionManager=CarrierAllocationServiceIntegrationTests.this.platformTransactionManager;
        TransactionTemplate transactionTemplate=new TransactionTemplate(platformTransactionManager);
        transactionTemplate.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED);
        Integer mySequenceNumber=transactionTemplate.execute(new TransactionCallback<Object>() {
            @Override
            public Object doInTransaction(TransactionStatus status) {
                    int res= sequenceService.issueSequenceNumber();
                    return res;

            }
        });
	logger.debug("Got number "+mySequenceNumber);
    }

I think I should be able to replace this use of transaction template with an @Transactional annotaion, so the above looks like this:-

@Transactional
public void callsIssueSequenceNumberAnnotaionVersion() {
	int mySequenceNumber= sequenceService.issueSequenceNumber();
	logger.debug("Got number "+mySequenceNumber);
}

But this doesn't work. The system timesout when trying to aquire the lock:-

javax.persistence.LockTimeoutException: Lock wait timeout exceeded; try restarting transaction

I don't see why why a lock timeout should ever occur here, I'm just testing the system, there is only one thread. I also don't see why Transaction template would work when @Transaction doesn't. Can anyone suggest what is wrong with the @Transactional way of calling issueSequenceNumber and what I could do to fix it?

Thanks for any help!