JFreeChart生成饼形及柱形图实例

在Java中利用JFreeChart可轻松生成各种统计分析图形，包括柱形图／饼图／曲线图／折线图／甘特图等，JFreeChart可从 http://www.jfree.org/jfreechart/<wbr></wbr>获得jar包，现在最新版本为JFreeChart 1.05。

一、从网站下载相关JAR包，关键包包括jfreechart-1.0.5.jar和jcommon-1.0.9.jar，将这两个JAR加到ECLIPSE项目的构建路径，并放到％TOMCAT_HOME％common/lib目录下，配置WEB项目的web.xml文件，加入以下代码：
<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>
配置以上servlet是为了在网页中正常显示图形，若配置不正确，图形将不会显示。

二、图形生成类ChartGenerater.java
import java.awt.Color;
import java.awt.Font;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import javax.servlet.http.HttpSession;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartRenderingInfo;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.CategoryAxis;
import org.jfree.chart.entity.StandardEntityCollection;
import org.jfree.chart.labels.StandardCategoryItemLabelGenerator;
import org.jfree.chart.labels.StandardPieToolTipGenerator;
import org.jfree.chart.plot.CategoryPlot;
import org.jfree.chart.plot.PiePlot3D;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.BarRenderer3D;
import org.jfree.chart.servlet.ServletUtilities;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.data.general.DefaultPieDataset;

/**
*
* @ 利用JFreeChart生成柱形及饼状图
* @versionJFreeChart 1.05 jcommon-1.0.9
* @author Jojoy
* @ List list 生成图形的源数据
* @ String titles 标题
* @ String x 图形的水平轴注释
* @ String y 图形的垂直轴注释
* @ String charttype 图形类型，piechart为饼图，barchart为柱形图
*/
public class ChartGenerater {
public static String generatePieChart(List list, String titles,
HttpSession session, PrintWriter pw, String x,String y,String charttype) {
String filename = null;
Font font;
if ("piechart".equals(charttype.trim())) {
try {
// 建立PieDataSet
DefaultPieDataset data = new DefaultPieDataset();
Iterator it = list.iterator();
while (it.hasNext()) {
Object[] rows = (Object[]) it.next();
String result = (String) rows[0];
int count = ((Integer) rows[1]).intValue();
data.setValue(result, count);
}
// 生成chart物件
PiePlot3D plot = new PiePlot3D(data);// 生成一个3D饼图
plot.setForegroundAlpha(0.6f);
plot.setToolTipGenerator(new StandardPieToolTipGenerator());
font = new Font("黑体", Font.CENTER_BASELINE, 20);// 这个地方是设置统计图标题的字体和大小
JFreeChart chart = new JFreeChart("",
JFreeChart.DEFAULT_TITLE_FONT, plot, true);
TextTitle tt = new TextTitle(titles);
tt.setFont(font);
chart.setBackgroundPaint(java.awt.Color.white);// 统计图片的底色
chart.setTitle(tt);
// 把生成的文件写入到临时的目录中
ChartRenderingInfo info = new ChartRenderingInfo(
new StandardEntityCollection());
filename = ServletUtilities.saveChartAsPNG(chart, 500, 300,
info, session);
// 选择存储成png格式的文件，当然你也可以使用saveChartAsJPEG的方法生成jpg图片
// 把image map 写入到 PrintWriter
ChartUtilities.writeImageMap(pw, filename, info, false);
pw.flush();
} catch (Exception ex) {
System.out.println("error:" + ex.getMessage());
}
}
if ("barchart".equals(charttype.trim())) {
try {
DefaultCategoryDataset dataset = new DefaultCategoryDataset();
Iterator it = list.iterator();
while (it.hasNext()) {
Object[] rows = (Object[]) it.next();
String author = (String) rows[0];
int count = ((Integer) rows[1]).intValue();
dataset.addValue(count, author, author);
}

//生成柱形图
JFreeChart chart = ChartFactory.createBarChart3D(titles,
x, y, dataset, PlotOrientation.VERTICAL,
true, false, false);
chart.setBackgroundPaint(Color.WHITE);
CategoryPlot plot = chart.getCategoryPlot();
CategoryAxis domainAxis = plot.getDomainAxis();
domainAxis.setAxisLineVisible(false);
plot.setDomainAxis(domainAxis);
BarRenderer3D renderer = new BarRenderer3D();
renderer.setBaseOutlinePaint(Color.BLACK);
// 设置每个地区所包含的平行柱的之间距离
renderer.setItemMargin(0.1);
// 显示每个柱的数值，并修改该数值的字体属性
renderer
.setItemLabelGenerator(new StandardCategoryItemLabelGenerator());
renderer.setItemLabelsVisible(true);
plot.setRenderer(renderer);
// 设置柱的透明度
plot.setForegroundAlpha(0.8f);
StandardEntityCollection sec = new StandardEntityCollection();
ChartRenderingInfo info = new ChartRenderingInfo(sec);

// 500是图片长度，300是图片高度
// String filename =
// ServletUtilities.saveChartAsPNG(chart,500,300,info,session);
filename = ServletUtilities.saveChartAsJPEG(chart, 500, 300,
info, session);
ChartUtilities.writeImageMap(pw, filename, info, false);
pw.flush();
}catch (Exception ex) {
System.out.println("error:" + ex.getMessage());
}
}
return filename;
}
}

三、JSP页面调用
<%
List list=(ArrayList)session.getAttribute("datalist");
String filename = ChartGenerater.generatePieChart(list,"信息发布结果统计",session, new PrintWriter(out),"","","piechart");
String graphURL = request.getContextPath() + "/servlet/DisplayChart?filename=" + filename;
%>
<table ALIGN="CENTER">
<tr>
<td>
<img src="<%= graphURL %>" width=500 height=300 border=0 usemap="#<%= filename %>">
</td>
</tr>
</table>