EDIT

package eu.etaxonomy.taxeditor.editor.handler;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

import java.util.UUID;

import org.eclipse.core.commands.AbstractHandler;

import org.eclipse.core.commands.ExecutionEvent;

import org.eclipse.core.commands.ExecutionException;

import org.eclipse.jface.viewers.ISelection;

import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.ui.PartInitException;

import org.eclipse.ui.handlers.HandlerUtil;

import eu.etaxonomy.cdm.model.description.IndividualsAssociation;

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

import eu.etaxonomy.taxeditor.editor.EditorUtil;

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

import eu.etaxonomy.taxeditor.model.MessagingUtils;

public class OpenDerivateViewHandler extends AbstractHandler {

    /* (non-Javadoc)

     * @see org.eclipse.core.commands.IHandler#execute(org.eclipse.core.commands.ExecutionEvent)

     */

    @Override

    public Object execute(ExecutionEvent event) throws ExecutionException {

        ISelection currentSelection = HandlerUtil.getCurrentSelection(event);

        if(currentSelection instanceof IStructuredSelection){

            Iterator<?> selectionIterator = ((IStructuredSelection) currentSelection).iterator();

            Set<UUID> selectedElementUUIDs = new HashSet<UUID>();

            while(selectionIterator.hasNext()){

                Object object = selectionIterator.next();

                if(object instanceof SpecimenOrObservationBase<?>){

                    selectedElementUUIDs.add(((SpecimenOrObservationBase<?>) object).getUuid());

                }

                else if(object instanceof IndividualsAssociation){

                    SpecimenOrObservationBase specimen = ((IndividualsAssociation) object).getAssociatedSpecimenOrObservation();

                    if(specimen!=null){

                        selectedElementUUIDs.add(specimen.getUuid());

                    }

                }

            }

            if(!selectedElementUUIDs.isEmpty()){

                DerivateViewEditorInput input = new DerivateViewEditorInput(selectedElementUUIDs);

                try {

                    EditorUtil.open(input);

                } catch (PartInitException e) {

                    MessagingUtils.error(OpenDerivateViewHandler.class, "Could not open Derivative Editor", e);

                } catch (NullPointerException npe){

                    MessagingUtils.messageDialog("Failed to open Editor", OpenDerivateViewHandler.class, "Could not open Derivative Editor. The derivate hierarchy is corrupted!", npe);

                }

            }

            else{

                MessagingUtils.informationDialog("Empty selection", "No Specimen selected.");

            }

        }

        return null;

    }

}