javsjava或 jsp 实现柱状图，饼状图
高手请进 求java或 jsp 实现柱状图、饼状图源码
或调试通过以下源码均给分，下面源码session是怎么回事情
package bean;
import java.awt.Font;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpSession;

import org.jfree.chart.ChartRenderingInfo;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.entity.StandardEntityCollection;
import org.jfree.chart.plot.PiePlot3D;
import org.jfree.chart.servlet.ServletUtilities;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.general.DefaultPieDataset;


public class PieChart
{
 //这个方法用来计算显示项数据所占比例
  private double getRatio(HashMap map, Object value)
  {
  double result = 0.00;
  double total = 0.00;
  String strTemp = "";
  Iterator iter = map.keySet().iterator();
  while (iter.hasNext())
  {
  Object key = iter.next();
  strTemp = (String) map.get(key);
  total += (Double.parseDouble(strTemp));
  }
  strTemp = (String) map.get(value);
  result = Double.parseDouble(strTemp) / total;
  //result = (double) Math.round(result);
  return result;
  }
  //创建绘制饼图
  public String JCreate(HashMap map, String title, HttpSession session, int w,int h)
  {
  DefaultPieDataset piedata = new DefaultPieDataset();
  //如果没有数据可以通过这一块来测试
  piedata.setValue("Google", 130);
  piedata.setValue("Baidu", 40.3);
  piedata.setValue("sohu", 19.6);
  // piedata.setValue("msn", 29.6);
   
  Iterator iter = map.keySet().iterator();
  while (iter.hasNext())
  {
  Object key = iter.next();
  piedata.setValue(key.toString(), getRatio(map, key));
  }

  // 3D饼图
  PiePlot3D plot = new PiePlot3D(piedata);
  // 饼图
  // PiePlot plot = new PiePlot(piedata);

  // 设定链接 ("link.jsp","section"));//section为参数，不填写则默认为category
  // plot.setURLGenerator(new StandardPieURLGenerator("link.jsp","section"));

  // 指定图片的透明度
  plot.setForegroundAlpha(1.0f);
  plot.setDepthFactor(0.08);

  // 指定显示的饼图上圆形(false)还椭圆形(true)
  plot.setCircular(false);

  // 显示百分比
  plot.setLabelGenerator(new
  StandardPieItemLabelGenerator(StandardPieItemLabelGenerator.DEFAULT_TOOLTIP_FORMAT));
  plot.setLegendLabelGenerator(new StandardPieItemLabelGenerator("{0}:({1}M, {2})"));

  JFreeChart chart = new JFreeChart("", JFreeChart.DEFAULT_TITLE_FONT, plot,true);
  // 设置图片背景色
  chart.setBackgroundPaint(java.awt.Color.white);

  // 设置图片标题属性
  Font font = new Font("黑体", Font.CENTER_BASELINE, 20);
  TextTitle _title = new TextTitle(title);
  _title.setFont(font);
  chart.setTitle(_title);

  plot.setToolTipGenerator(new StandardPieItemLabelGenerator());
  // 把生成的图片放到临时目录
  StandardEntityCollection sec = new StandardEntityCollection();
  ChartRenderingInfo info = new ChartRenderingInfo(sec);

  String filename =