关于JFreeChart

最近做了个综合查询,要求出柱状图,所以上网找了一下,记录了一个最简单易懂的,是developWorks上的
1.
在web.xml中加入如下的servlet

<servlet>
   <servlet-name>DisplayChart</servlet-name>
   <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
</servlet>
<servlet-mapping>
   <servlet-name>DisplayChart</servlet-name>
   <url-pattern>/servlet/DisplayChart</url-pattern>
</servlet-mapping>

2.
在jsp页面写如下代码
<%@ page contentType="text/html; charset=GB2312" %>
<%@ page import="org.jfree.chart.ChartFactory,
org.jfree.chart.JFreeChart,
org.jfree.chart.plot.PlotOrientation,
org.jfree.chart.servlet.ServletUtilities,
org.jfree.data.DefaultCategoryDataset"%>
<%
DefaultCategoryDataset dataset = new DefaultCategoryDataset();
dataset.addValue(300, "", "1月份");
dataset.addValue(200, "", "2月份");
dataset.addValue(430, "", "3月份");
dataset.addValue(390, "", "4月份");
dataset.addValue(280, "", "5月份");
dataset.addValue(240, "", "6月份");

JFreeChart chart = ChartFactory.createBarChart3D("水果销售统计图",
"月份",
"销量",
dataset,
PlotOrientation.VERTICAL,
false,
true,
false);

String filename = ServletUtilities.saveChartAsPNG(chart, 500, 300, null, session);
String graphURL = request.getContextPath() + "/DisplayChart?filename=" + filename;
%>
<img src="<%= graphURL %>" width=500 height=300 border=0 usemap="#<%= filename %>">
3.
注意:filename这个名字要固定,就这样写