code: @Override
  	public void update(Object entity) {
  		ResourceManager<Transaction> manager = managers.get(keyValue(entity));
  		
  		if (manager == null) {
  			throw new IllegalStateException("Log ["
  					+ Log.Operation.UPDATE
  					+ "] is not allowed: previous operation must be ["
  					+ Log.Operation.GET + "]");
  		}
  		
  		manager.update(entity);
  		Log log = new Log(transaction.logs().size() + 1, Log.Operation.UPDATE, entity);
  		log.state(State.UNCOMMITTED);
  		transaction.logs().add(log);
  		logger.fine("Transaction [" + transaction.id() + "]: Entity [" + entity + "] has been updated");
  	}
docs: Updates the entity in the datastore with the specified one within the
  current transaction.
  
  @param entity The entity to be updated to.