JFreeChart—输出折线图

实现代码：

LineChartServlet.java

[code]package com.lmb.jfreechart;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.io.IOException;
import java.util.Date;

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.plot.CategoryPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.renderer.category.LineAndShapeRenderer;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.category.CategoryDataset;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.ui.HorizontalAlignment;
import org.jfree.ui.RectangleEdge;

public class LineChartServlet extends HttpServlet {

    private static final long serialVersionUID = 1585397081043433662L;

    public LineChartServlet() {
        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.createLineChart("08年图书销售量",
                null, "销售量", dataset, PlotOrientation.VERTICAL, false, true,
                false);
        // 设置图表的子标题
        jfreechart.addSubtitle(new TextTitle("按月份"));
        // 创建一个标题
        TextTitle texttitle = new TextTitle("日期: " + new Date());
        // 设置标题字体
        texttitle.setFont(new Font("黑体", 0, 10));
        // 设置标题向下对齐
        texttitle.setPosition(RectangleEdge.BOTTOM);
        // 设置标题向右对齐
        texttitle.setHorizontalAlignment(HorizontalAlignment.RIGHT);
        // 添加图表的子标题
        jfreechart.addSubtitle(texttitle);
        // 设置图表的背景色为白色
        jfreechart.setBackgroundPaint(Color.white);
        // 获得图表区域对象
        CategoryPlot categoryplot = (CategoryPlot) jfreechart.getPlot();
        categoryplot.setBackgroundPaint(Color.lightGray);
        categoryplot.setRangeGridlinesVisible(false);
        // 获显示线条对象
        LineAndShapeRenderer lineandshaperenderer = (LineAndShapeRenderer) categoryplot
                .getRenderer();
        lineandshaperenderer.setBaseShapesVisible(true);
        lineandshaperenderer.setDrawOutlines(true);
        lineandshaperenderer.setUseFillPaint(true);
        lineandshaperenderer.setBaseFillPaint(Color.white);
        // 设置折线加粗
        lineandshaperenderer.setSeriesStroke(0, new BasicStroke(3F));
        lineandshaperenderer.setSeriesOutlineStroke(0, new BasicStroke(2.0F));
        // 设置折线拐点
        lineandshaperenderer.setSeriesShape(0,
                new java.awt.geom.Ellipse2D.Double(-5D, -5D, 10D, 10D));

        // 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() {
        DefaultCategoryDataset defaultdataset = new DefaultCategoryDataset();
        for (int i = 1; i <= 12; i++) {
            defaultdataset.addValue(DataUtils.getRandomData(), "J***A", i + "月");
            defaultdataset.addValue(DataUtils.getRandomData(), "PHP", i + "月");

        }
        return defaultdataset;
    }

}

web.xml略。。。

总结：

1、利用CategoryGataSet数据集绘制折线图；

2、对应创建折线图的方法是createLineChart()；

3、通过TextTitle对象设置图表的子标题；

4、利用LineAndShapeRenderer线条对象，设置折线的显示方式。