用JFreeChart生成的表没有每个项的数量

我是看到这个链接做的

http://hi.baidu.com/python811022/item/3f01cc25194c0d102b0f1c38

下面是我写的servlet

package com.xiaolu.web.servlet;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.jfree.chart.ChartRenderingInfo;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.entity.StandardEntityCollection;
import org.jfree.chart.labels.StandardPieToolTipGenerator;
import org.jfree.chart.plot.PiePlot3D;
import org.jfree.data.general.DefaultPieDataset;

public class JfreeChartDemo extends HttpServlet{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //数据源
        DefaultPieDataset data = new DefaultPieDataset();
        data.setValue("高中以下",370); 
        data.setValue("高中",1530); 
        data.setValue("大专",5700); 
        data.setValue("本科",8280); 
        data.setValue("硕士",4420); 
        data.setValue("博士",80); 
        //3D饼图
        PiePlot3D plot = new PiePlot3D(data);
        plot.setToolTipGenerator(new StandardPieToolTipGenerator()); 
        JFreeChart chart = new JFreeChart("程序员学历情况调查表", JFreeChart.DEFAULT_TITLE_FONT, plot, true);
        chart.setBackgroundPaint(java.awt.Color.white);//可选，设置图片背景色 
        StandardEntityCollection sec = new StandardEntityCollection(); 
        ChartRenderingInfo info = new ChartRenderingInfo(sec); 
        String path = this.getServletContext().getRealPath("/image");
        String file = path+"\\chart1.jpg";
        ChartUtilities.saveChartAsJPEG(new File(file), chart, 500, 300,info);
        request.setAttribute("url", file);
        request.getRequestDispatcher("/index.jsp").forward(request, response);
    }
    
}