【JFreeChart】JFreeChart—输出区域图

﹏ヽ暗。殇╰゛Y 2022-08-01 11:09 169阅读 0赞

区域图（Area Chart）与折线图类似，但其强调数据之间的变化幅度，能够直观的现实变化的区域。

# 实现代码： #

**AreaChartServlet.java**

package com.lmb.jfreechart;
    
    import java.awt.Color;
    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.ChartFactory;
    import org.jfree.chart.ChartUtilities;
    import org.jfree.chart.JFreeChart;
    import org.jfree.chart.axis.CategoryAxis;
    import org.jfree.chart.axis.CategoryLabelPositions;
    import org.jfree.chart.plot.CategoryPlot;
    import org.jfree.chart.plot.PlotOrientation;
    import org.jfree.data.category.CategoryDataset;
    import org.jfree.data.category.DefaultCategoryDataset;
    import org.jfree.ui.RectangleInsets;
    
    public class AreaChartServlet extends HttpServlet {
        
    
        private static final long serialVersionUID = 5852523271721922574L;
        public AreaChartServlet() {
            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");
            // 获取数据集对象
            CategoryDataset dataset = createDataset();
            // 创建图形对象
            JFreeChart jfreechart = ChartFactory.createAreaChart("08年图书销售量排名",
                    "按季度", "销量", dataset, PlotOrientation.VERTICAL, true, true,
                    false);
            // 获得图表区域对象
            CategoryPlot categoryplot = (CategoryPlot) jfreechart.getPlot();
            //设置前景色为50%透明
            categoryplot.setForegroundAlpha(0.5F);
            //设置X轴偏移量
            categoryplot.setAxisOffset(new RectangleInsets(5D, 5D, 5D, 5D));
            //设置北景色为浅灰色
            categoryplot.setBackgroundPaint(Color.lightGray);
            //设置显示网格线
            categoryplot.setDomainGridlinesVisible(true);
            //设置网格线为白色
            categoryplot.setDomainGridlinePaint(Color.white);
            //设置显示边界线
            categoryplot.setRangeGridlinesVisible(true);
            //设置显示边界线为白色
            categoryplot.setRangeGridlinePaint(Color.white);
            //获得X轴对象
            CategoryAxis categoryaxis = categoryplot.getDomainAxis();
            //设置X轴标签位置为45度角
            categoryaxis.setCategoryLabelPositions(CategoryLabelPositions.UP_45);
            //设置与X轴的补白为0
            categoryaxis.setLowerMargin(0.0D);
            categoryaxis.setUpperMargin(0.0D);
    
            // 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、利用CategoryDataset数据集绘制区域图；

2、对应创建区域图的方法是createAreaChart()；

3、利用CategoryAxis对象设置绘制区域的显示方式；