EDIT

import java.util.List;

import java.util.Set;

import org.apache.log4j.Logger;

    private static final Logger logger = Logger.getLogger(TaxonNameEditorPresenter.class);

    @Override

    protected TaxonName handleTransientProperties(TaxonName bean) {

        logger.trace(this._toString() + ".onEditorSaveEvent - handling transient properties");

        List<TaxonName> newBasionymNames = getView().getBasionymCombobox().getValueFromNestedFields();

        Set<TaxonName> oldBasionyms = bean.getBasionyms();

        boolean updateBasionyms = false;

        for(TaxonName newB : newBasionymNames){

            updateBasionyms = updateBasionyms || !oldBasionyms.contains(newB);

        }

        for(TaxonName oldB : oldBasionyms){

            updateBasionyms = updateBasionyms || !newBasionymNames.contains(oldB);

        }

        if(updateBasionyms){

            bean.removeBasionyms();

            for(TaxonName basionymName :newBasionymNames){

                getSession().merge(basionymName);

                bean.addBasionym(basionymName);

            }

        }

        return bean;

    }

import java.util.ArrayList;

import java.util.HashSet;

import java.util.Set;

import com.vaadin.data.Validator.InvalidValueException;

import eu.etaxonomy.vaadin.mvp.AbstractCdmEditorPresenter;

    private Set<F> nestedFields = new HashSet<>() ;

            nestedFields .add(field);

    /**

     * {@inheritDoc}

     */

    @Override

    public void commit() throws SourceException, InvalidValueException {

        nestedFields.forEach(f -> f.commit());

        // calling super.commit() is useless if operating on a transient property!!

        super.commit();

    }

    /**

     * Obtains the List of values directly from the nested fields and ignores the

     * value of the <code>propertyDataSource</code>. This is useful when the ToManyRelatedEntitiesListSelect

     * is operating on a transient field, in which case the property is considered being read only by vaadin

     * so that the commit is doing nothing.

     *

     * See also {@link AbstractCdmEditorPresenter#handleTransientProperties(DTO bean)}

     *

     * @return

     */

    public List<V> getValueFromNestedFields() {

        List<V> nestedValues = new ArrayList<>();

        nestedFields.forEach(f -> nestedValues.add(f.getValue()));

        return nestedValues;

    }

    @SuppressWarnings("unchecked")

    @Override

    @EventListener // the generic type parameter <DTO> must not be used here otherwise events will not be received

    public void onEditorPreSaveEvent(EditorPreSaveEvent preSaveEvent){

        if(!isFromOwnView(preSaveEvent)){

            return;

        }

        logger.trace(this._toString() + ".onEditorPreSaveEvent - starting transaction");

        tx = startTransaction();

        // merge the bean and update the fieldGroup with the merged bean, so that updating

        // of field values in turn of the commit are can not cause LazyInitializationExeptions

        // the bean still has the original values at this point

        logger.trace(this._toString() + ".onEditorPreSaveEvent - merging bean into session");

        mergedBean((DTO) preSaveEvent.getBean());

    }

    @SuppressWarnings("unchecked")

        DTO bean = (DTO) saveEvent.getBean();

        bean = handleTransientProperties(bean);

        // merge the changes into the session, ...

        DTO mergedBean = mergedBean(bean);

        getRepo().getCommonService().saveOrUpdate(mergedBean);

        eventBus.publishEvent(new EntityChangeEvent(mergedBean.getClass(), mergedBean.getId(), changeEventType));

    }

    /**

     * EditorPresneters for beans with transient properties should overwrite this method to

     * update the beanItem with the changes made to the transient properties.

     * <p>

     * This is necessary because Vaadin MethodProperties are readonly when no setter is

     * available. This can be the case with transient properties. Automatic updating

     * of the property during the fieldGroup commit does not work in this case.

     */

    protected DTO handleTransientProperties(DTO bean) {

        // no need to handle transient properties in the generic case

        return bean;