EDIT

      <handlers xmi:id="_mrTfkDonEeecLdI14WMq7w" elementId="eu.etaxonomy.taxeditor.editor.view.derivate.handler.AddDnaSampleHandler" contributionURI="bundleclass://eu.etaxonomy.taxeditor.editor/eu.etaxonomy.taxeditor.editor.view.derivate.handler.AddDnaSampleHandler" command="_jsbToDonEeecLdI14WMq7w"/>

          <children xsi:type="menu:HandledMenuItem" xmi:id="_UukRoDmBEeeOos_QXKSXcA" elementId="eu.etaxonomy.taxeditor.editor.handledmenuitem.dnasample" label="DNA Sample" command="_jsbToDonEeecLdI14WMq7w"/>

    <elements xsi:type="commands:Command" xmi:id="_jsbToDonEeecLdI14WMq7w" elementId="eu.etaxonomy.taxeditor.editor.command.add_derivate.add_dna_sample" commandName="Add DNA Sample"/>

package eu.etaxonomy.taxeditor.editor.view.derivate.handler;

import javax.inject.Named;

import org.eclipse.e4.core.di.annotations.CanExecute;

import org.eclipse.e4.core.di.annotations.Execute;

import org.eclipse.e4.ui.model.application.ui.basic.MPart;

import org.eclipse.e4.ui.model.application.ui.menu.MHandledMenuItem;

import org.eclipse.e4.ui.services.IServiceConstants;

import org.eclipse.jface.viewers.TreeNode;

import eu.etaxonomy.cdm.api.facade.DerivedUnitFacadeCacheStrategy;

import eu.etaxonomy.cdm.api.service.IOccurrenceService;

import eu.etaxonomy.cdm.model.occurrence.DerivationEvent;

import eu.etaxonomy.cdm.model.occurrence.DerivationEventType;

import eu.etaxonomy.cdm.model.occurrence.DerivedUnit;

import eu.etaxonomy.cdm.model.occurrence.SpecimenOrObservationBase;

import eu.etaxonomy.taxeditor.editor.view.derivate.DerivateView;

import eu.etaxonomy.taxeditor.model.MessagingUtils;

import eu.etaxonomy.taxeditor.store.CdmStore;

public abstract class AbstractAddDerivativeHandler {

	@Execute

	public void execute(@Named(IServiceConstants.ACTIVE_SELECTION) TreeNode node, @Named(IServiceConstants.ACTIVE_PART) MPart part) {

	    DerivateView derivateView = (DerivateView) part.getObject();

	    checkDirtyState(derivateView);

	    Object selectedDerivative = node.getValue();

	    if(isAllowed(selectedDerivative)){

	        Object createdElement = addElement(selectedDerivative);

	        refreshView(derivateView, createdElement);

	    }

	}

    @CanExecute

    public boolean canExecute(@Named(IServiceConstants.ACTIVE_SELECTION) TreeNode node, MHandledMenuItem item) {

        boolean canExecute = false;

        Object derivate = node.getValue();

        canExecute = isAllowed(derivate);

        item.setVisible(canExecute);

        return canExecute;

    }

    private void refreshView(DerivateView derivateView, Object createdElement) {

        if(derivateView!=null){

            derivateView.getConversationHolder().commit();

            derivateView.refreshTree(createdElement);

        }

    }

	private void checkDirtyState(DerivateView derivateView){

	        if(derivateView!=null){

	            if(derivateView.isDirty()){

	                MessagingUtils.warningDialog(DerivateView.VIEW_HAS_UNSAVED_CHANGES, this, DerivateView.YOU_NEED_TO_SAVE_BEFORE_PERFORMING_THIS_ACTION);

	                return;

	            }

	        }

	}

	private Object addElement(Object selectedDerivative){

	    Object createdElement = null;

	    SpecimenOrObservationBase<?> specimenOrObservationBase = (SpecimenOrObservationBase<?>) selectedDerivative;

	    DerivedUnit derivedUnit = createDerivative();

	    specimenOrObservationBase.addDerivationEvent(DerivationEvent.NewSimpleInstance(specimenOrObservationBase, derivedUnit, getDerivationeType()));

	    derivedUnit.setCacheStrategy(new DerivedUnitFacadeCacheStrategy());

	    derivedUnit.getTitleCache(); //update title cache

	    createdElement = derivedUnit;

	    CdmStore.getService(IOccurrenceService.class).merge((SpecimenOrObservationBase<?>) selectedDerivative, true);

	    return createdElement;

	}

	protected abstract DerivedUnit createDerivative();

	protected abstract DerivationEventType getDerivationeType();

    protected abstract boolean isAllowed(Object derivative);

}

package eu.etaxonomy.taxeditor.editor.view.derivate.handler;

import eu.etaxonomy.cdm.model.molecular.DnaSample;

import eu.etaxonomy.cdm.model.occurrence.DerivationEventType;

import eu.etaxonomy.cdm.model.occurrence.DerivedUnit;

import eu.etaxonomy.cdm.model.occurrence.FieldUnit;

import eu.etaxonomy.cdm.model.occurrence.SpecimenOrObservationType;

public class AddDnaSampleHandler extends AbstractAddDerivativeHandler{

    @Override

    protected boolean isAllowed(Object derivative) {

        if(derivative instanceof FieldUnit || (derivative instanceof DerivedUnit

                && ((DerivedUnit) derivative).getRecordBasis().equals(SpecimenOrObservationType.PreservedSpecimen))

                || (derivative instanceof DerivedUnit

                        && ((DerivedUnit) derivative).getRecordBasis().equals(SpecimenOrObservationType.TissueSample))){

            return true;

        }

        return false;

    }

    /**

     * {@inheritDoc}

     */

    @Override

    protected DerivedUnit createDerivative() {

        return DnaSample.NewInstance();

    }

    /**

     * {@inheritDoc}

     */

    @Override

    protected DerivationEventType getDerivationeType() {

        return DerivationEventType.ACCESSIONING();

    }

}

import eu.etaxonomy.cdm.model.occurrence.DerivedUnit;

public class AddSpecimenHandler extends AbstractAddDerivativeHandler{

    protected DerivedUnit createDerivative() {

        return DerivedUnit.NewInstance(SpecimenOrObservationType.PreservedSpecimen);

public class AddTissueSampleHandler extends AbstractAddDerivativeHandler{

    protected DerivedUnit createDerivative() {

        return DerivedUnit.NewInstance(SpecimenOrObservationType.TissueSample);