JFreeChart是老牌Java开源图表工具包，也是JFreeReport的重要组成部分，在业界被广泛应用。当然，这个工具包依然有很多美中不足，确切的说，有很多具体的应用还需要我们拓展，比如蜘蛛网图（Spider Web）的刻度问题。
带刻度问题比较复杂，JFreeChart本身没有提供其功能，需要继承SpiderWebPlot，覆盖drawLabel方法。
开发中需要用到jcommon-1.0.16.jar和jfreechart-1.0.13.jar
为了方便我只提供Struts下的ACTION中需要用到的生成图表的类中的全部代码
public class MySpiderWebPlot extends SpiderWebPlot {
/**
*
*/
private static final long serialVersionUID = 4005814203754627127L;
private int ticks = DEFAULT_TICKS;
private static final int DEFAULT_TICKS = 5;
private NumberFormat format = NumberFormat.getInstance();
private static final double PERPENDICULAR = 90;
private static final double TICK_SCALE = 0.015;
private int valueLabelGap = DEFAULT_GAP;
private static final int DEFAULT_GAP = 10;
private static final double THRESHOLD = 15;
MySpiderWebPlot(CategoryDataset createCategoryDataset) {
super(createCategoryDataset);
}
@Override
protected void drawLabel(final Graphics2D g2, final Rectangle2D plotArea, final double value,
final int cat, final double startAngle, final double extent) {
super.drawLabel(g2, plotArea, value, cat, startAngle, extent);
final FontRenderContext frc = g2.getFontRenderContext();
final double[] transformed = new double[2];
final double[] transformer = new double[2];
final Arc2D arc1 = new Arc2D.Double(plotArea, startAngle, 0, Arc2D.OPEN);
for (int i = 1; i <= ticks; i++) {
final Point2D point1 = arc1.getEndPoint();
final double deltaX = plotArea.getCenterX();
final double deltaY = plotArea.getCenterY();
double labelX = point1.getX() - deltaX;
double labelY = point1.getY() - deltaY;
final double scale = ((double) i / (double) ticks);
final AffineTransform tx = AffineTransform.getScaleInstance(scale, scale);
final AffineTransform pointTrans = AffineTransform.getScaleInstance(scale + TICK_SCALE, scale + TICK_SCALE);
transformer[0] = labelX;
transformer[1] = labelY;
pointTrans.transform(transformer, 0, transformed, 0, 1);
final double pointX = transformed[0] + deltaX;
final double pointY = transformed[1] + deltaY;
tx.transform(transformer, 0, transformed, 0, 1);
labelX = transformed[0] + deltaX;
labelY = transformed[1] + deltaY;
double rotated = (PERPENDICULAR);
AffineTransform rotateTrans = AffineTransform.getRotateInstance(Math.toRadians(rotated), labelX, labelY);
transformer[0] = pointX;
transformer[1] = pointY;
rotateTrans.transform(transformer, 0, transformed, 0, 1);
final double x1 = transformed[0];
final double y1 = transformed[1];
rotated = (-PERPENDICULAR);
rotateTrans = AffineTransform.getRotateInstance(Math.toRadians(rotated), labelX, labelY);
rotateTrans.transform(transformer, 0, transformed, 0, 1);
final Composite saveComposite = g2.getComposite();
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1.0f));
g2.draw(new Line2D.Double(transformed[0], transformed[1], x1, y1));
if (startAngle == this.getStartAngle()) {
final String label = format.format(((double) i / (double) ticks) * this.getMaxValue());
final LineMetrics lm = getLabelFont().getLineMetrics(label, frc);
final double ascent = lm.getAscent();
if (Math.abs(labelX - plotArea.getCenterX()) < THRESHOLD) {
labelX += valueLabelGap;
labelY += ascent / (float) 2;
} else if (Math.abs(labelY - plotArea.getCenterY()) < THRESHOLD) {
labelY += valueLabelGap;
} else if (labelX >= plotArea.getCenterX()) {
if (labelY < plotArea.getCenterY()) {
labelX += valueLabelGap;
labelY += valueLabelGap;
} else {
labelX -= valueLabelGap;
labelY += valueLabelGap;
}
} else {
if (labelY > plotArea.getCenterY()) {
labelX -= valueLabelGap;
labelY -= valueLabelGap;
} else {
labelX += valueLabelGap;
labelY -= valueLabelGap;
}
}
g2.setPaint(getLabelPaint());
g2.setFont(getLabelFont());
g2.drawString(label, (float) labelX, (float) labelY);
}
g2.setComposite(saveComposite);
}
}
}
public class MySpriderWebPlotTest {
public static void main(String args[]) {
//在SWING中显示
JFrame jf = new JFrame();
jf.add(erstelleSpinnenDiagramm());
jf.pack();
jf.setVisible(true);
//将JFreeChart保存为图片存在文件路径中
saveAsFile("E:/JfreeChart/MySpiderWebPlot.png",500,400);
}
public static JPanel erstelleSpinnenDiagramm() {
JFreeChart jfreechart =createChart();
ChartPanel chartpanel = new ChartPanel(jfreechart);
return chartpanel;
}
public static void saveAsFile(String outputPath,
int weight, int height) {
FileOutputStream out = null;
try {
File outFile = new File(outputPath);
if (!outFile.getParentFile().exists()) {
outFile.getParentFile().mkdirs();
}
out = new FileOutputStream(outputPath);
// 保存为PNG
ChartUtilities.writeChartAsPNG(out, createChart(),weight, height);
// 保存为JPEG
// ChartUtilities.writeChartAsJPEG(out, chart, 500, 400);
out.flush();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
// do nothing
}
}
}
}
public static JFreeChart createChart() {
MySpiderWebPlot spiderwebplot = new MySpiderWebPlot(createDataset());
JFreeChart jfreechart = new JFreeChart("前三个季度水果销售报告", TextTitle.DEFAULT_FONT,spiderwebplot, false);
LegendTitle legendtitle = new LegendTitle(spiderwebplot);
legendtitle.setPosition(RectangleEdge.BOTTOM);
jfreechart.addSubtitle(legendtitle);
return jfreechart;
}
public static DefaultCategoryDataset createDataset() {
DefaultCategoryDataset dataset = new DefaultCategoryDataset();
String group1 = "苹果 ";
dataset.addValue(5, group1, "一月份");
dataset.addValue(6, group1, "二月份");
dataset.addValue(4, group1, "三月份");
dataset.addValue(2, group1, "四月份");
dataset.addValue(5, group1, "五月份");
dataset.addValue(5, group1, "六月份");
dataset.addValue(5, group1, "七月份");
dataset.addValue(8, group1, "八月份");
String group2 = "橙子";
dataset.addValue(3, group2, "一月份");
dataset.addValue(3, group2, "二月份");
dataset.addValue(4, group2, "三月份");
dataset.addValue(7, group2, "四月份");
dataset.addValue(4, group2, "五月份");
dataset.addValue(5, group2, "六月份");
dataset.addValue(3, group2, "七月份");
dataset.addValue(3, group2, "八月份");
String group3 = "香蕉";
dataset.addValue(4, group3, "一月份");
dataset.addValue(5, group3, "二月份");
dataset.addValue(2, group3, "三月份");
dataset.addValue(5, group3, "四月份");
dataset.addValue(6, group3, "五月份");
dataset.addValue(6, group3, "六月份");
dataset.addValue(4, group3, "七月份");
dataset.addValue(4, group3, "八月份");
return dataset;
}
}
顺便说下，在开发中我常用到的生成jFreeChart的步骤有三个，首先我会先创建数据集合DataSet，然后通过数据集合我会创建jFreeChart对象，最后我会通过jFreeChart提供的ChartUtilities类的writeChartAsPNG()方法将创建为图片保存到磁盘文件中，如果保存到与项目相对路径的话在WEB页面就可以呈现出我们生成的jFreeChart图片了！
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