在这里主要贴上JFreeChart做的两个小例子，分别是柱状图和动态显示JVM内存状况图。
先说明一下jfreechart的概念，jfreechart工具基本上把一个图形分成了几个逻辑部分：
1.首先是整个的画布对象(chart)，画布就相当与一个大的容器，包含一些图形元素，比如为一张白纸
2.然后是画图区域对象(plot)，就是实际图形所占据的区域，比如为白纸上的一个长方形
3.然后是图形所需要两条轴对象(axis)，比如为白纸上的两条轴线
4.最后是如何进行图像的绘制对象(render)，比如为一只画图的笔
5.除开上面的这些对象，还有一个最主要的就是通过必须的数据集(dataset)来生成图形了
好了，其它的API就看文档了。现在开始说开发JFreeChart例子的步骤：
1. 首先下载jfreechart包。
2. 接着用MyEclipse创建一个Java Project.
3. 引用包, 要加入的包是gnujaxp.jar, jfreechart-1.0.12.jar, jcommon-1.0.15.jar
这样就把开发环境配好了，接下来就是创建类文件。先从柱状图开始.
import java.io.FileOutputStream;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.category.CategoryDataset;
import org.jfree.data.category.DefaultCategoryDataset;
public class BarChartDemo {
private static String rowKeys[] ={"Apple", "Banana", "Watermelon"};
private static String columnKeys[] ={"Guangzhou", "Shanghai", "Beijing"};
private static String rowKeys_zh_CN[] ={"苹果", "香蕉", "西瓜"};
private static String columnKeys_zh_CN[] ={"广州", "上海", "北京"};
/**
* @param args
*/
public static void main(String[] args) {
CategoryDataset dataSet = getComplexDataSet();
JFreeChart chart = ChartFactory.createBarChart("Fruit Output Chart",// 图表标题
"Fruit",// 目录轴的显示标签
"Output",// 数值轴的显示标签
dataSet,// 数据集
PlotOrientation.VERTICAL,// 图表方向：水平、垂直
true,// 是否显示图例(对于简单的柱状图必须是false)
false,// 是否生成工具
false// 是否生成URL链接
);
FileOutputStream fosJPG = null;
try {
fosJPG = new FileOutputStream("D:\\fruit.jpg");
ChartUtilities.writeChartAsJPEG(fosJPG, chart, 400, 300);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
fosJPG.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
/**
* 获取一个演示用的简单数据集对象
*
* @return
*/
private static CategoryDataset getDataSet() {
DefaultCategoryDataset categoryDataset = new DefaultCategoryDataset();
categoryDataset.addValue(100, "", rowKeys[0]);
categoryDataset.addValue(200, "", rowKeys[1]);
categoryDataset.addValue(300, "", rowKeys[2]);
return categoryDataset;
}
/**
* 获取一个演示用的组合数据集对象
*
* @return
*/
private static CategoryDataset getComplexDataSet() {
DefaultCategoryDataset categoryDataset = new DefaultCategoryDataset();
categoryDataset.addValue(100, columnKeys[0], rowKeys[0]);
categoryDataset.addValue(110, columnKeys[1], rowKeys[0]);
categoryDataset.addValue(120, columnKeys[2], rowKeys[0]);
categoryDataset.addValue(200, columnKeys[0], rowKeys[1]);
categoryDataset.addValue(210, columnKeys[1], rowKeys[1]);
categoryDataset.addValue(220, columnKeys[2], rowKeys[1]);
categoryDataset.addValue(300, columnKeys[0], rowKeys[2]);
categoryDataset.addValue(310, columnKeys[1], rowKeys[2]);
categoryDataset.addValue(320, columnKeys[2], rowKeys[2]);
return categoryDataset;
}
}
运行后，可看到结果了。
接着下来是动态显示JVM内存状况图的原码.
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.time.Millisecond;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.ui.RectangleInsets;
public class MemoryUsage extends JPanel {
class DataGenerator extends Timer implements ActionListener {
/*
* Invoked when an action occurs.
*
* @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
public void actionPerformed(ActionEvent actionevent) {
long free = Runtime.getRuntime().freeMemory();
long total = Runtime.getRuntime().totalMemory();
addTotalObservation(total);
addFreeObservation(free);
}
DataGenerator(int i) {
super(i, null);
addActionListener(this);
}
}
public MemoryUsage(int maxItemAge) {
super(new BorderLayout());
total = new TimeSeries("Total Memory",
org.jfree.data.time.Millisecond.class);
total.setMaximumItemAge(maxItemAge);
free = new TimeSeries("Free Memory",
org.jfree.data.time.Millisecond.class);
free.setMaximumItemAge(maxItemAge);
TimeSeriesCollection timeseriescollection = new TimeSeriesCollection();
timeseriescollection.addSeries(total);
timeseriescollection.addSeries(free);
DateAxis dateaxis = new DateAxis("Time");
NumberAxis numberaxis = new NumberAxis("Memory");
dateaxis.setTickLabelFont(new Font("SansSerif", 0, 12));
numberaxis.setTickLabelFont(new Font("SansSerif", 0, 12));
dateaxis.setLabelFont(new Font("SansSerif", 0, 14));
numberaxis.setLabelFont(new Font("SansSerif", 0, 14));
dateaxis.setAutoRange(true);
dateaxis.setLowerMargin(0.0D);
dateaxis.setUpperMargin(0.0D);
dateaxis.setTickLabelsVisible(true);
numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());
XYLineAndShapeRenderer xylineandshaperenderer = new XYLineAndShapeRenderer(
true, false);
xylineandshaperenderer.setSeriesPaint(0, Color.RED); // 改变第一个Series的颜色
xylineandshaperenderer.setSeriesPaint(1, Color.YELLOW);// 改变第二个Series的颜色
xylineandshaperenderer.setSeriesStroke(0, new BasicStroke(1F, 0, 2));
xylineandshaperenderer.setSeriesStroke(1, new BasicStroke(1F, 0, 2));
XYPlot xyplot = new XYPlot(timeseriescollection, dateaxis, numberaxis,
xylineandshaperenderer);
xyplot.setBackgroundPaint(Color.BLACK); // 改变背景颜色
xyplot.setDomainGridlinePaint(Color.white);
xyplot.setRangeGridlinePaint(Color.white);
xyplot.setAxisOffset(new RectangleInsets(1D, 1D, 1D, 1D));
JFreeChart jfreechart = new JFreeChart("JVM Memory Usage", new Font(
"SansSerif", 1, 24), xyplot, true);
jfreechart.setBackgroundPaint(Color.white);
ChartPanel chartpanel = new ChartPanel(jfreechart, true);
chartpanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory
.createEmptyBorder(10, 10, 10, 10), BorderFactory
.createLineBorder(Color.black)));
add(chartpanel);
}
private void addTotalObservation(double d) {
total.add(new Millisecond(), d);
}
private void addFreeObservation(double d) {
free.add(new Millisecond(), d);
}
/**
* @param args
*/
public static void main(String[] args) {
JFrame jframe = new JFrame("JVM Memory Usage");
MemoryUsage memoryusagedemo = new MemoryUsage(10000);
jframe.getContentPane().add(memoryusagedemo, "Center");
jframe.setBounds(200, 120, 1000, 500);
jframe.setVisible(true);
(memoryusagedemo.new DataGenerator(1000)).start();
jframe.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent windowevent) {
System.exit(0);
}
});
}
private TimeSeries total;
private TimeSeries free;
}
