public String generateXYAreaChart(
      HttpSession session, PrintWriter pw, String courseId, int studentId) {
    String filename = null;
    /* int groupId=0;
    if (groupName.equals("All")){
        groupId=0;
    }else{
         groupId = studStatisticBean.getGroupIdByName(groupName);
    }*/

    try {
      //  Retrieve list of WebHits for each section and populate a TableXYDataset
      StudentsConceptChartDataSet cDataSet =
          new StudentsConceptChartDataSet(studStatisticBean, courseId, studentId);
      // cDataSet.setStudentStatisticBeanIdRef(studStatisticBean);
      ArrayList sections = cDataSet.getSections();
      Iterator sectionIter = sections.iterator();
      DefaultTableXYDataset dataset = new DefaultTableXYDataset();
      while (sectionIter.hasNext()) {
        String section = (String) sectionIter.next();
        ArrayList list = cDataSet.getDataByHitConcept(section);
        XYSeries dataSeries = new XYSeries(section, true, false);
        Iterator webHitIter = list.iterator();
        while (webHitIter.hasNext()) {
          StudentsConceptHit cHit = (StudentsConceptHit) webHitIter.next();
          dataSeries.add(cHit.getOrdNumb(), cHit.getHitDegree());
        }
        dataset.addSeries(dataSeries);
      }

      //  Throw a custom NoDataException if there is no data
      if (dataset.getItemCount() == 0) {
        System.out.println("No data has been found");
        throw new NoDataException();
      }

      //  Create tooltip and URL generators
      SimpleDateFormat sdf = new SimpleDateFormat("dd-MMM-yyyy", Locale.UK);
      StandardXYToolTipGenerator ttg =
          new StandardXYToolTipGenerator(
              StandardXYToolTipGenerator.DEFAULT_TOOL_TIP_FORMAT, sdf, NumberFormat.getInstance());
      TimeSeriesURLGenerator urlg =
          new TimeSeriesURLGenerator(sdf, "bar_chart.jsp", "series", "hitDate");

      //  Create the X-Axis
      DateAxis xAxis = new DateAxis(null);
      xAxis.setLowerMargin(0.0);
      xAxis.setUpperMargin(0.0);

      //  Create the X-Axis
      NumberAxis yAxis = new NumberAxis(null);
      yAxis.setAutoRangeIncludesZero(true);

      //  Create the renderer
      StackedXYAreaRenderer renderer =
          new StackedXYAreaRenderer(XYAreaRenderer.AREA_AND_SHAPES, ttg, urlg);
      renderer.setSeriesPaint(0, new Color(255, 255, 180));
      renderer.setSeriesPaint(1, new Color(206, 230, 255));
      renderer.setSeriesPaint(2, new Color(255, 230, 230));
      renderer.setSeriesPaint(3, new Color(206, 255, 206));
      renderer.setShapePaint(Color.gray);
      renderer.setShapeStroke(new BasicStroke(0.5f));
      renderer.setShape(new Ellipse2D.Double(-3, -3, 6, 6));
      renderer.setOutline(true);

      //  Create the plot
      XYPlot plot = new XYPlot(dataset, xAxis, yAxis, renderer);
      plot.setForegroundAlpha(0.65f);

      //  Reconfigure Y-Axis so the auto-range knows that the data is stacked
      yAxis.configure();

      //  Create the chart
      JFreeChart chart = new JFreeChart(null, JFreeChart.DEFAULT_TITLE_FONT, plot, true);
      chart.setBackgroundPaint(java.awt.Color.white);

      //  Write the chart image to the temporary directory
      ChartRenderingInfo info = new ChartRenderingInfo(new StandardEntityCollection());
      filename = ServletUtilities.saveChartAsPNG(chart, 600, 400, info, session);

      //  Write the image map to the PrintWriter
      ChartUtilities.writeImageMap(pw, filename, info);
      pw.flush();

    } catch (NoDataException e) {
      System.out.println(e.toString());
      filename = "public_nodata_500x300.png";
    } catch (Exception e) {
      System.out.println("Exception - " + e.toString());
      e.printStackTrace(System.out);
      filename = "public_error_500x300.png";
    }
    return filename;
  }