ClassCastException error in reading session.

Hi guys,

I have some problem implementing an open source cewolf software into my program. I need to generate graph based on result that is getting from database selection (anotner class). Then I passed the result in a session to the graph class. But it seems that the class cannot read the session value. Below I paste my jsp and my class. Java error message is also paste below.
Hope any experts out there can help me.

zamir

Java Error Messages:
[code]
java.lang.ClassCastException
      at de.laures.cewolf.example.PageViewCountData.produceDataset(PageViewCountData.java:64)
      at de.laures.cewolf.taglib.DataContainer.getDataset(DataContainer.java:53)
      at de.laures.cewolf.taglib.SimpleChartDefinition.getDataset(SimpleChartDefinition.java:34)
      at de.laures.cewolf.taglib.util.PageUtils.getDataset(PageUtils.java:58)
      at de.laures.cewolf.taglib.tags.ChartMapTag.doStartTag(ChartMapTag.java:71)

[/code]

myjsp:
[code]
<%@taglib uri='/WEB-INF/cewolf.tld' prefix='cewolf' %>
<%@taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@page import="eplan.graph.business.*" %>
<%@page import="java.io.Serializable"%>

<% //Object theObj = session.getAttribute("theObjectsName") %>
<% HttpSession getSession= request.getSession(false); %>
<% GraphByFruit[] theObj = (GraphByFruit[])session.getAttribute("GraphData");%>
<% //System.out.print("GraphByFruit[] theObj ="+theObj+"\n");%>

<jsp:useBean id="categoryDataGraph" class="de.laures.cewolf.example.PageViewCountData"/>
<!-- Bar Graph -->
<p>
<div align="center">
<cewolf:chart id="horizontalBarChart" title="Anggaran Pengeluaran Buah-Buahan Bermusim" type="horizontalBar" xaxislabel="Mont$
    <cewolf:data>
        <cewolf:producer id="categoryDataGraph">
        <cewolf:param name="graphSession" value="<%=theObj%>"/>
        <!--cewolf:param name="graphSession" value='<%//=(GraphByFruit)session.getAttribute("GraphData") %>'/-->
        </cewolf:producer>
    </cewolf:data>
</cewolf:chart>

<cewolf:img chartid="horizontalBarChart" renderer="cewolf" width="750" height="500">
    <cewolf:map tooltipgeneratorid="categoryToolTipGenerator" linkgeneratorid="categoryLink"/>
</cewolf:img>
</div>
</p>
[/code]

myclass:

[code]
package de.laures.cewolf.example;

import java.util.Date;
import java.util.Map;
import java.io.Serializable;
import org.jfree.data.CategoryDataset;
import org.jfree.data.DefaultCategoryDataset;
import de.laures.cewolf.DatasetProduceException;
import de.laures.cewolf.DatasetProducer;
import de.laures.cewolf.CategoryItemLinkGenerator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jfree.chart.tooltips.CategoryToolTipGenerator;
import eplan.graph.business.GraphByFruit;
import javax.servlet.http.*;

/**
 * An example data producer.
 * @author  Guido Laures
 * @modified by Zamir A Jalil
 */
public class PageViewCountData implements DatasetProducer,CategoryItemLinkGenerator,CategoryToolTipGenerator,Serializable
{

    private static final Log log = LogFactory.getLog(PageViewCountData.class);

    // These values would normally not be hard coded but produced by
    // some kind of data source like a database or a file
    private final String[] categories =    {"mon","tue","wen","thu","fri","sat","sun","mon","tue","wen","thu","fri"};
    String[] arrayOfFruit;


        /**
         *  Produces some random data.
         */
    public Object produceDataset(Map params) throws DatasetProduceException {

        int month = 0;
        float[] qty = null;

        System.out.print ("\n\n/**************************************************************/\n");
        HttpSession graphsession = (HttpSession)params.get("graphSession");
        //System.out.print ("HttpSession graphsession ="+graphsession+"\n");

        GraphByFruit[] graph = (GraphByFruit[])graphSession.getAttribute("GraphData");;

        final String[] arrayOfFruit = new String[graph.length];

        log.debug("producing data.");
        DefaultCategoryDataset datagraph = new DefaultCategoryDataset(){
                        /**
                         * @see java.lang.Object#finalize()
                         */
                        protected void finalize() throws Throwable {
                                super.finalize();
                                log.debug(this +" finalized.");
                        }
        };
        for (int series = 0; series < arrayOfFruit.length; series ++) {
            arrayOfFruit[series] = graph[series].getFruitName();
            qty = graph[series].getProdQty();
            float[] lastY = qty;
            for (int i = 0; i < categories.length; i++) {
                final float y = qty[i];
                //lastY = y;
                datagraph.addValue((double)y, arrayOfFruit[series], categories[i]);
            }
        }
        return datagraph;
    }

    /**
     * This producer's data is invalidated after 5 seconds. By this method the
     * producer can influence Cewolf's caching behaviour the way it wants to.
     */
        public boolean hasExpired(Map params, Date since) {
        log.debug(getClass().getName() + "hasExpired()");
                return (System.currentTimeMillis() - since.getTime())  > 5000;
        }

        /**
         * Returns a unique ID for this DatasetProducer
         */
        public String getProducerId() {
                return "GraphSessionDataSetProducer";
        }

    /**
     * Returns a link target for a special data item.
     */
    public String generateLink(Object data, int series, Object category) {
        return arrayOfFruit[series];
    }

        /**
         * @see java.lang.Object#finalize()
         */
        protected void finalize() throws Throwable {
                super.finalize();
                log.debug(this + " finalized.");
        }

        /**
         * @see org.jfree.chart.tooltips.CategoryToolTipGenerator#generateToolTip(CategoryDataset, int, int)
         */
        public String generateToolTip(CategoryDataset arg0, int series, int arg2) {
                return arrayOfFruit[series];
        }

}
[/code]