      昨天听到“数据下探”这个名词，结果一问才发现是这样的一回事，就是在图表上，例如柱状图上点击一个柱子，跳转到另一个图表页面。昨天看了一下JFreeChart，发现可以StandardCategoryURLGenerator类来实现这个功能，昨天做了个简单的demo，效果还不错，呵呵，共享一下。
     首先建立一个名为barSample的web项目，并将jfreechart1.0.6的相关包加入到其中，本人在该项目中加入的jar包如下：
     （1）gnujaxp.jar；
     （2）itext-2.0.2.jar；
     （3）jcommon-1.0.10.jar；
     （4）jfreechart-1.0.6.jar；
     （5）jfreechart-1.0.6-experimental.jar；
     （6）jfreechart-1.0.6-swt.jar；
     （7）servlet.jar；
     （8）swtgraphics2d.jar。
      并在web.xml中加入相关的配置，配置后的web.xml的内容如下：

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.4"

xmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee

http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet-name>DisplayChart</servlet-name>

<servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>DisplayChart</servlet-name>

<url-pattern>/DisplayChart</url-pattern>

</servlet-mapping>

</web-app>

在WebRoot目录下建立index.jsp，显示第一个图表，该柱状图的每根柱子都添加了链接，该页面的代码如下：

<%@ page contentType="text/html;charset=GBK"%>

<%@ page import="java.awt.Color,

org.jfree.chart.ChartFactory,

org.jfree.chart.JFreeChart,

org.jfree.chart.plot.PlotOrientation,

org.jfree.chart.servlet.ServletUtilities,

org.jfree.data.category.CategoryDataset,

org.jfree.data.general.*,

org.jfree.chart.plot.CategoryPlot,

org.jfree.chart.axis.CategoryAxis,

org.jfree.chart.axis.ValueAxis,

org.jfree.chart.renderer.category.BarRenderer3D,

org.jfree.chart.urls.StandardCategoryURLGenerator,

org.jfree.chart.*,

org.jfree.chart.entity.*,

org.jfree.chart.labels.*"%>

java.io.PrintWriter pw=new java.io.PrintWriter(out);

double[][] data = new double[][] {{672}, {325}, {332}, {440}, {550}, {330}};

String[] rowKeys = {"苹果", "梨子", "葡萄", "桔子", "西瓜", "香蕉"};

String[] columnKeys = {""};

CategoryDataset dataset = DatasetUtilities.createCategoryDataset(

rowKeys,

columnKeys,

data);

JFreeChart chart = ChartFactory.createBarChart3D("水果销量图统计",

"水果",

"销量",

dataset,

PlotOrientation.VERTICAL,

true,

false,

false);

chart.setBackgroundPaint(Color.WHITE);

CategoryPlot plot = chart.getCategoryPlot();

CategoryAxis domainAxis = plot.getDomainAxis();

plot.setDomainAxis(domainAxis);

ValueAxis rangeAxis = plot.getRangeAxis();

//设置最高的一个 Item 与图片顶端的距离

rangeAxis.setUpperMargin(0.15);

//设置最低的一个 Item 与图片底端的距离

rangeAxis.setLowerMargin(0.15);

plot.setRangeAxis(rangeAxis);

BarRenderer3D renderer = new BarRenderer3D();

renderer.setBaseOutlinePaint(Color.BLACK);

//设置 Wall 的颜色

renderer.setWallPaint(Color.gray);

//设置每种水果代表的柱的颜色

renderer.setSeriesPaint(0, new Color(0, 0, 255));

renderer.setSeriesPaint(1, new Color(200, 200, 255));

renderer.setSeriesPaint(2, Color.GREEN);

renderer.setSeriesPaint(3, Color.MAGENTA);

renderer.setSeriesPaint(4, Color.GRAY);

renderer.setSeriesPaint(5, Color.CYAN);

//设置平行柱的之间距离

renderer.setItemMargin(0.3);

//显示每个柱的数值

renderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator());

renderer.setBaseItemLabelsVisible(true);

renderer.setBaseItemURLGenerator(new StandardCategoryURLGenerator(

"detail.jsp", "fruit", ""));

plot.setRenderer(renderer);

//设置柱的透明度

plot.setForegroundAlpha(0.5f);

//设置地区、销量的显示位置

//plot.setRangeAxisLocation(AxisLocation.BOTTOM_OR_RIGHT);

ChartRenderingInfo info = new ChartRenderingInfo(new

StandardEntityCollection());

String filename = ServletUtilities.saveChartAsPNG(chart, 800, 600, info, session);

String graphURL = request.getContextPath() + "/DisplayChart?filename=" + filename;

ChartUtilities.writeImageMap(pw, filename, info, true);

pw.flush();

<tr>

<img src="<%= graphURL %>" width=800 height=600 border=0 usemap="#<%= filename %>" alt="">

</td>

</tr>

</table>

链接到的详情页面detail.jsp的内容如下所示：

<%@ page contentType="text/html;charset=GBK"%>

<%@ page import="java.awt.Color,

org.jfree.chart.ChartFactory,

org.jfree.chart.JFreeChart,

org.jfree.chart.plot.PlotOrientation,

org.jfree.chart.servlet.ServletUtilities,

org.jfree.data.category.CategoryDataset,

org.jfree.data.general.*,

org.jfree.chart.plot.CategoryPlot,

org.jfree.chart.axis.CategoryAxis,

org.jfree.chart.axis.ValueAxis,

org.jfree.chart.renderer.category.BarRenderer3D,

org.jfree.chart.labels.*"%>

String fruit = new String(request.getParameter("fruit").getBytes("ISO8859_1"), "utf-8");

int count = 0;

if ("苹果".equals(fruit)) {

count = 100;

} else if ("梨子".equals(fruit)) {

count = 26;

} else if ("葡萄".equals(fruit)) {

count = -20;

} else if ("桔子".equals(fruit)) {

count = -40;

} else if ("西瓜".equals(fruit)) {

count = 80;

}

//String address = new String(request.getParameter("address").getBytes("ISO8859_1"), "utf-8");

double[][] data = new double[][] {{672 + count}, {325 + count}, {332 + count}, {440 + count},

{550 + count}, {330 + count}, {435 + count}, {553 + count},

{335 + count}, {443 + count}, {378 + count}, {733 + count}};

String[] rowKeys = {"一月份", "二月份", "三月份", "四月份",

"五月份", "六月份", "七月份", "八月份",

"九月份", "十月份", "十一月份", "十二月份"};