Vaddin Container - Custom sorting by converted property

CustomItemSorter.java

import java.util.Comparator;

import com.vaadin.data.Container.Sortable;
import com.vaadin.data.Item;
import com.vaadin.data.Property;
import com.vaadin.data.util.DefaultItemSorter;

/**
 * The original need for this class is to provide a way of sorting by converted values instead of only the underlying
 * property values. Sometimes a property is converted to be entirely different than the underlying property, and the
 * user should see sorting based on what is visible. For example, a location ID property that is converted to a name
 * label name needs this, but likely date/time does not need this.
 */
public abstract class CustomItemSorter extends DefaultItemSorter {
    private static final long serialVersionUID = 1L;

    protected Comparator<Object> propertyValueComparator = new DefaultPropertyValueComparator();

    @Override
    final public void setSortProperties(Sortable container, Object[] propertyId, boolean[] ascending) {
        super.setSortProperties(container, propertyId, ascending);
        customSetup(container, propertyId, ascending);
    }

    /**
     * Called just before sorting takes place.
     */
    protected abstract void customSetup(Sortable container, Object[] propertyId, boolean[] ascending);

    /**
     * Taken from super.
     */
    @Override
    final protected int compareProperty(Object propertyId, boolean sortDirection, Item item1, Item item2) {

        // Get the properties to compare
        final Property<?> property1 = item1.getItemProperty(propertyId);
        final Property<?> property2 = item2.getItemProperty(propertyId);

        // Get the values to compare
        Object value1 = (property1 == null) ? null : property1.getValue();
        Object value2 = (property2 == null) ? null : property2.getValue();

        // START CUSTOMIZATION
        value1 = handleProperty(propertyId, value1);
        value2 = handleProperty(propertyId, value2);
        // END CUSTOMIZATION

        // Result of the comparison
        int r = 0;
        if (sortDirection) {
            r = propertyValueComparator.compare(value1, value2);
        } else {
            r = propertyValueComparator.compare(value2, value1);
        }

        return r;
    }

    /**
     * This will be called against both compared properties. Return the value that you want used in compare.
     */
    protected abstract Object handleProperty(Object propertyId, Object value);
}