【JFreeChart】JFreeChart—输出组合图表

向右看齐 2022-08-01 11:10 228阅读 0赞

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。