EDIT

    <elements xsi:type="commands:Command" xmi:id="_eTTa4C0vEeiiqYcnQ2drEA" elementId="eu.etaxonomy.taxeditor.openSpecimenEditorForGatheringEvent" commandName="Open specimen editor for gathering event"/>

    <elements xsi:type="commands:Handler" xmi:id="_jkqm0C0vEeiiqYcnQ2drEA" elementId="eu.etaxonomy.taxeditor.editor.view.derivate.handler.OpenDerivativeEditorForGatheringEvent" contributionURI="bundleclass://eu.etaxonomy.taxeditor.editor/eu.etaxonomy.taxeditor.editor.view.derivate.handler.OpenDerivativeEditorForGatheringEvent" command="_eTTa4C0vEeiiqYcnQ2drEA"/>

      <viewCommandMapping

            commandId="eu.etaxonomy.taxeditor.openSpecimenEditorForGatheringEvent"

            selection="eu.etaxonomy.cdm.model.occurrence.GatheringEvent"

            viewerName="%viewCommandMapping.viewerName.SPECIMEN_EDITOR">

      </viewCommandMapping>

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

import java.util.ArrayList;

import java.util.Collection;

import java.util.List;

import java.util.UUID;

import org.eclipse.e4.ui.workbench.modeling.EPartService;

import org.eclipse.swt.widgets.Shell;

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

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

import eu.etaxonomy.cdm.hibernate.HibernateProxyHelper;

import eu.etaxonomy.cdm.model.common.ICdmBase;

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

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

import eu.etaxonomy.taxeditor.editor.EditorUtil;

import eu.etaxonomy.taxeditor.editor.l10n.Messages;

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

import eu.etaxonomy.taxeditor.handler.defaultHandler.e4.DefaultOpenHandlerBaseE4;

import eu.etaxonomy.taxeditor.store.CdmStore;

public class OpenDerivativeEditorForGatheringEvent extends DefaultOpenHandlerBaseE4<GatheringEvent> {

    protected static final String OPEN_DERIVATIVE_EDITOR_FOR_TAXON_NODE_COULD_NOT_OPEN = Messages.OpenDerivativeEditorForTaxonNode_COULD_NOT_OPEN;

    @Override

    protected GatheringEvent getEntity(UUID uuid) {

        ICdmBase load = CdmStore.getService(IEventBaseService.class).load(uuid);

        return HibernateProxyHelper.deproxy(load, GatheringEvent.class );

    }

    @Override

    protected void open(GatheringEvent entity, Shell shell, EPartService partService) {

        Collection<UUID> specimenUuids = new ArrayList<UUID>();

        List<FieldUnit> fieldUnits = CdmStore.getService(IOccurrenceService.class).getFieldUnitsForGatheringEvent(entity.getUuid());

        fieldUnits.forEach(fieldUnit->specimenUuids.add(fieldUnit.getUuid()));

        DerivateViewEditorInput input = new DerivateViewEditorInput(specimenUuids);

        EditorUtil.openSpecimenEditor(input, modelService, partService, application);

    }

    /**

     * {@inheritDoc}

     */

    @Override

    protected boolean canExecute(GatheringEvent entity) {

        return true;

    }

}