JFreeChart—输出组合图表

组合图表（Combined Chart）可以组合不同的图形，例如柱状图和折线图等，通常显示股票的图，比如上方式股票价格，下方是成交量。

实现代码：

CombinedChartServlet.java

package com.lmb.jfreechart;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.jfree.chart.ChartUtilities;import org.jfree.chart.JFreeChart;import org.jfree.chart.axis.CategoryAxis;import org.jfree.chart.axis.NumberAxis;import org.jfree.chart.labels.StandardCategoryToolTipGenerator;import org.jfree.chart.plot.CategoryPlot;import org.jfree.chart.plot.CombinedDomainCategoryPlot;import org.jfree.chart.renderer.category.BarRenderer;import org.jfree.chart.renderer.category.LineAndShapeRenderer;import org.jfree.data.category.CategoryDataset;import org.jfree.data.category.DefaultCategoryDataset;public class CombinedChartServlet extends HttpServlet {    private static final long serialVersionUID = -566713680648708515L;    public CombinedChartServlet() {        super();    }    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        this.doPost(request, response);    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        // 设置返回类型为图片        response.setContentType("image/png");        // 创建第一个数据集        CategoryDataset categorydataset = createDataset();        NumberAxis numberaxis = new NumberAxis("销量");        numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());        LineAndShapeRenderer lineandshaperenderer = new LineAndShapeRenderer();        CategoryPlot categoryplot = new CategoryPlot(categorydataset, null,                numberaxis, lineandshaperenderer);        categoryplot.setDomainGridlinesVisible(true);        // 创建第二个数据集        CategoryDataset categorydataset1 = createDataset();        NumberAxis numberaxis1 = new NumberAxis("销量");        BarRenderer barrenderer = new BarRenderer();        barrenderer                .setBaseToolTipGenerator(new StandardCategoryToolTipGenerator());        CategoryPlot categoryplot1 = new CategoryPlot(categorydataset1, null,                numberaxis1, barrenderer);        categoryplot1.setDomainGridlinesVisible(true);        // 创建组合数据集        CategoryAxis categoryaxis = new CategoryAxis();        CombinedDomainCategoryPlot combineddomaincategoryplot = new CombinedDomainCategoryPlot(                categoryaxis);        combineddomaincategoryplot.add(categoryplot, 2);        combineddomaincategoryplot.add(categoryplot1, 1);        // 创建图表对象        JFreeChart jfreechart = new JFreeChart("组合图", null,                combineddomaincategoryplot, true);        // 将图表已数据流的方式返回给客户端        ChartUtilities.writeChartAsPNG(response.getOutputStream(), jfreechart,                500, 270);    }    /**     * 返回数据集     *      * @return     */    private static CategoryDataset createDataset() {        // 时间维度        String[] category1 = { "第一季度", "第二季度", "第三季度", "第四季度" };        // 分类维度        String[] category2 = { "JAVA", "C/C++", "PHP" };        DefaultCategoryDataset defaultdataset = new DefaultCategoryDataset();        for (int i = 0; i < category1.length; i++) {            String category = category1[i];            for (int j = 0; j < category2.length; j++) {                String cat = category2[j];                // 模拟添加数据                defaultdataset.addValue(DataUtils.getRandomData(), cat,                        category);            }        }        return defaultdataset;    }}

web.xml略。。。

总结：

1、组合图的数据集主要有两个以上的数据集组成，通过CombinedDomainCategoryPlot对象的add(）方法，将不同的数据集装载；

2、创建组合图使用JFreeChart对象的构造方法创建。