Wicket and JFreeChart integration including image map for tooltips and clickable graph

DynamicImageMap.java

import org.apache.wicket.ajax.AjaxEventBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.IAjaxCallDecorator;
import org.apache.wicket.ajax.calldecorator.CancelEventIfNoAjaxDecorator;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.markup.repeater.Item;
import org.apache.wicket.markup.repeater.RefreshingView;
import org.apache.wicket.markup.repeater.util.ModelIteratorAdapter;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.jfree.chart.entity.ChartEntity;

import java.util.Collection;
import java.util.Iterator;

/**
 * Wicket markup container that produces an image map dynamically
 * from the given model
 *
 * @author Jonny Wray
 */
public abstract class DynamicImageMap extends WebMarkupContainer {

    private String mapName;

    public DynamicImageMap(String id, String mapName, IModel<Collection<ChartEntity>> model){
        super(id, model);
        this.mapName = mapName;
        RefreshingView mapAreas = new RefreshingView("areas", model){

            @Override
            protected Iterator getItemModels() {
                Collection<ChartEntity> chartEntityCollection = (Collection<ChartEntity>)getDefaultModelObject();
                return new ModelIteratorAdapter(chartEntityCollection.iterator()){
                    @Override
                    protected IModel model(Object object) {
                        return new Model((ChartEntity)object);
                    }
                };
            }

            @Override
            protected void populateItem(Item item) {
                final ChartEntity entity = (ChartEntity)item.getModelObject();
                WebMarkupContainer area = new WebMarkupContainer("area"){

                    @Override
                    protected void onComponentTag(final ComponentTag tag){
                        super.onComponentTag(tag);
                        assert tag.getName().equals("area");
                        tag.put("shape", entity.getShapeType());
		                tag.put("coords", entity.getShapeCoords());
		                tag.put("href", "#");
                        String tooltipText = entity.getToolTipText();
		                if(tooltipText != null && !tooltipText.isEmpty()){
			                tag.put("title", tooltipText);
		                }
                    }
                };
                area.add(new AjaxEventBehavior("onclick"){
				    private static final long serialVersionUID = 2615093257359874075L;

                    @Override
                    protected void onEvent(AjaxRequestTarget target) {
                        onClickCallback(target, entity);
                    }

                    protected IAjaxCallDecorator getAjaxCallDecorator(){
                        return new CancelEventIfNoAjaxDecorator();
                    }

                });
                item.add(area);
            }
        };
        add(mapAreas);
    }

    public abstract void onClickCallback(AjaxRequestTarget target, ChartEntity entity);

	@Override
	protected void onComponentTag(final ComponentTag tag){
		super.onComponentTag(tag);
		assert tag.getName().equals("map");
		tag.put("name", mapName);
	}
}

JFreeChartRenderingBean.java

import org.apache.wicket.markup.html.image.resource.BufferedDynamicImageResource;
import org.apache.wicket.markup.html.image.resource.DynamicImageResource;
import org.jfree.chart.ChartRenderingInfo;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.entity.ChartEntity;
import org.jfree.chart.entity.EntityCollection;

import java.awt.image.BufferedImage;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;

/**
 * Bean that holds the information and logic needed to render
 * a JFreeChart to an image. Used as a model object to enable
 * dynamic redrawing of an chart image.
 *
 * @author Jonny Wray
 */
public class JFreeChartRenderingBean implements Serializable{
    private ChartRenderingInfo renderingInfo = new ChartRenderingInfo();
    private BufferedDynamicImageResource imageResource;
    private JFreeChart chart;
    private int width;
    private int height;

    /**
     * Construct the rendering bean
     *
     * @param chart The chart to render
     * @param width The width to render to
     * @param height The height to render to
     */
    public JFreeChartRenderingBean(JFreeChart chart, int width, int height){
        this.chart = chart;
        this.width = width;
        this.height = height;
    }

    public DynamicImageResource getImageResource(){
        if(imageResource == null){
            renderingInfo.clear();
            BufferedImage image = chart.createBufferedImage(width, height, renderingInfo);
            imageResource = new BufferedDynamicImageResource();
            imageResource.setImage(image);
        }
        return imageResource;
    }

    public Collection<ChartEntity> getChartEntities(){
        if(imageResource == null){
            getImageResource(); // Force the image to be rendered
        }
        Collection<ChartEntity> chartEntities = new ArrayList<ChartEntity>();
        EntityCollection entities = renderingInfo.getEntityCollection();
        if (entities != null) {
            int count = entities.getEntityCount();
            for (int i = count - 1; i >= 0; i--) {
                ChartEntity entity = entities.getEntity(i);
                chartEntities.add(entity);
            }
        }
        return chartEntities;
    }
}

MappedJFreeChartPanel.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:wicket="http://wicket.apache.org/dtds.data/wicket-xhtml1.3-strict.dtd" xml:lang="en" lang="en">
	<wicket:panel>
        <span>
            <img style="vertical-align: middle;" wicket:id="image" />
            <map wicket:id="imageMap" >
                <span wicket:id="areas">
                    <area wicket:id="area" />
                </span>
            </map>
        </span>
	</wicket:panel>
</html>

MappedJFreeChartPanel.java

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.markup.html.image.NonCachingImage;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.apache.wicket.model.PropertyModel;
import org.jfree.chart.entity.ChartEntity;

import java.util.UUID;

/**
 * Wicket panel that includes a JFreeChart as an image with an
 * associated image map used for tooltips and clicks.
 *
 * @author Jonny Wray
 */
public class MappedJFreeChartPanel extends Panel {

    public MappedJFreeChartPanel(final String id, final IModel<JFreeChartRenderingBean> model){
        super(id, model);
        String mapName = getPath() + UUID.randomUUID().toString(); // UUID allows use in a repeater

        NonCachingImage chartImage = new NonCachingImage("image", new PropertyModel(model, "imageResource"));
		chartImage.add(new AttributeModifier("usemap", true, new Model("#"+mapName)));
        add(chartImage);
        DynamicImageMap imageMap = new DynamicImageMap("imageMap", mapName, new PropertyModel(model, "chartEntities")){
            @Override
            public void onClickCallback(AjaxRequestTarget target, ChartEntity entity) {
                onClick(target, entity);
            }
        };
        add(imageMap);
    }

    /**
     * Do nothing implementation of an onClick callback for a chart entity. Override to
     * implement Ajax onclick functionality
     *
     * @param target The Ajax request
     * @param entity The chart entity clicked on
     */
    protected void onClick(AjaxRequestTarget target, ChartEntity entity){

    }
}