Java API for vaadin-grid-sorter component

GridSorter.java

package org.vaadin.addons.tatu;

import com.vaadin.flow.component.Component;
import com.vaadin.flow.component.ComponentEvent;
import com.vaadin.flow.component.ComponentEventListener;
import com.vaadin.flow.component.Tag;
import com.vaadin.flow.component.html.Span;
import com.vaadin.flow.data.provider.SortDirection;
import com.vaadin.flow.shared.Registration;

@Tag("vaadin-grid-sorter")
public class GridSorter extends Component {

    SortDirection direction;
    private Integer order;

    public GridSorter(String header) {
        Span span = new Span(header);
        getElement().appendChild(span.getElement());
        direction = getDirection();
        getElement().addEventListener("click", e -> {
            if (direction == null) {
                direction = SortDirection.ASCENDING;
            } else if (direction == SortDirection.ASCENDING) {
                direction = SortDirection.DESCENDING;
            } else {
                direction = null;
            }
            fireEvent(new SorterChangedEvent<>(this, true));
        });
    }

    public void setDirection(SortDirection direction) {
        this.direction = direction;
        if (direction == SortDirection.ASCENDING) {
            getElement().setAttribute("direction", "asc");
        } else if (direction == SortDirection.DESCENDING) {
            getElement().setAttribute("direction", "desc");
        } else {
            getElement().removeAttribute("direction");
        }
    }

    public SortDirection getDirection() {
        return direction;
    }

    public void setOrder(Integer order) {
        this.order = order;
        if (order != null) {
            getElement().setProperty("order", order);
        } else {
            getElement().removeProperty("order");
        }
    }

    public Integer getOrder() {
        return order;
    }

    public Registration addSorterChangedListener(
            ComponentEventListener<SorterChangedEvent<GridSorter>> listener) {
        return addListener(SorterChangedEvent.class,
                (ComponentEventListener) listener);
    }

    public static class SorterChangedEvent<R extends GridSorter>
            extends ComponentEvent<GridSorter> {

        public SorterChangedEvent(GridSorter source, boolean fromClient) {
            super(source, fromClient);
        }

    }

}