一个另类而简单的蜘蛛图

首先是填写数据和生成图像的Java类(可以根据实际情况用在action里):

import java.awt.Color;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpSession;
import org.jfree.chart.ChartRenderingInfo;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.entity.StandardEntityCollection;
import org.jfree.chart.labels.StandardCategoryToolTipGenerator;
import org.jfree.chart.plot.SpiderWebPlot;
import org.jfree.chart.servlet.ServletUtilities;
import org.jfree.chart.title.TextTitle;
import org.jfree.data.category.CategoryDataset;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.util.Rotation;

public class CreateChart {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private static CategoryDataset createDataset() {
		String s = "First";
		String s3 = "Category 1";
		String s4 = "Category 2";
		String s5 = "Category 3";
		String s6 = "Category 4";
		String s7 = "Category 5";
		DefaultCategoryDataset defaultcategorydataset = new DefaultCategoryDataset();
		
		defaultcategorydataset.addValue(80D, s, s3);
		defaultcategorydataset.addValue(40D, s, s4);
		defaultcategorydataset.addValue(30D, s, s5);
		defaultcategorydataset.addValue(50D, s, s6);
		defaultcategorydataset.addValue(90D, s, s7);
		return defaultcategorydataset;
	}

	private static JFreeChart createChart(CategoryDataset categorydataset) {
		SpiderWebPlot spiderwebplot = new SkillScorePlot(categorydataset);
		spiderwebplot.setStartAngle(45D);
		categorydataset.getValue(0, 1);
		
		spiderwebplot.setBackgroundPaint(Color.LIGHT_GRAY);
		spiderwebplot.setMaxValue(100D);
		spiderwebplot.setDirection(Rotation.ANTICLOCKWISE);
		spiderwebplot.setAxisLinePaint(Color.blue);
		spiderwebplot.setInteriorGap(0.3D);
		spiderwebplot.setToolTipGenerator(new StandardCategoryToolTipGenerator());
		JFreeChart jfreechart = new JFreeChart("Competency Overall",TextTitle.DEFAULT_FONT, spiderwebplot, false);
		jfreechart.setBackgroundPaint(Color.cyan);
		return jfreechart;
	}

		
	
	public String getSpiderChart(HttpSession session, PrintWriter printWriter){
		
		JFreeChart jfreeChart = createChart(createDataset());
		ChartRenderingInfo info = new ChartRenderingInfo(new StandardEntityCollection());
		String fileName = null;
		try {
			fileName = ServletUtilities.saveChartAsPNG(jfreeChart, 500, 300, info,
					session);// 生成图片
			// Write the image map to the PrintWriter
			ChartUtilities.writeImageMap(printWriter, fileName, info, false);
		} catch (IOException e) {
			e.printStackTrace();
		}
		printWriter.flush();
		return fileName;// 返回生成图片的文件名
	}

}

因为要用到显示数据的标签,必须重写SpiderWebPlot类的drawLabel方法:

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.font.FontRenderContext;
import java.awt.font.LineMetrics;
import java.awt.font.TextAttribute;
import java.awt.geom.Arc2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.HashMap;
import org.jfree.chart.plot.SpiderWebPlot;
import org.jfree.data.category.CategoryDataset;

/**
 * 
 * @author Vincent.zheng this class is for draw the label.
 * 
 */
public class SkillScorePlot extends SpiderWebPlot {

	private static final long serialVersionUID = 1L;

	/**
	 * @param LABELANDAXISGAP : the gap between the label and the axis.
	 * @param LABELANDCENTERGAP : the gap between the label and the center point.
	 */
	private static final double LABELANDAXISGAP = 10;
	private static final double LABELANDCENTERGAP = 1;

	public SkillScorePlot(CategoryDataset categorydataset) {
		super(categorydataset);
	}

	/**
	 * @param extent : the angle gap between two near axis.
	 */
	@Override
	protected void drawLabel(Graphics2D graphics2D, Rectangle2D rectangle2D,
			double value, int cat, double startAngle, double extent) {

		super
				.drawLabel(graphics2D, rectangle2D, value, cat, startAngle,
						extent);

		/**
		 * @param sumAxisNum : the sum number of the axis.
		 * @param centerX : the center X coordinate of the panel.
		 * @param centerY : the center Y coordinate of the panel.
		 */
		int sumAxisNum = this.getDataset().getColumnCount();
		double centerX = rectangle2D.getCenterX();
		double centerY = rectangle2D.getCenterY();
		Arc2D arc2D;
		FontRenderContext fontRenderContext = graphics2D.getFontRenderContext();

		for (int currentAxisNum = 0; currentAxisNum < sumAxisNum; currentAxisNum++) {

			/**
			 * @param currentValue : the value of the current axis.
			 * @param label : the value on the label.
			 * @param scale : the scale of the point value to the max value on
			 *            current axis.
			 */
			double currentValue = this.getDataset().getValue(0, currentAxisNum).doubleValue();
			String label = String.valueOf((int) currentValue);
			double scale = (currentValue / this.getMaxValue());
			/**
			 * the coordinate of the label
			 */

			if (startAngle == this.getStartAngle()) {
				double labelX;
				double labelY;
				/**
				 * @param currentAngle : the angle of the current axis where the label place.
				 */
				double currentAngle = extent * currentAxisNum + startAngle;
				arc2D = new Arc2D.Double(rectangle2D, currentAngle, 0, Arc2D.OPEN);
				Point2D point2D = arc2D.getEndPoint();
				double axisX = Math.abs(point2D.getX() - centerX)* scale;
				double axisY = Math.abs(point2D.getY() - centerY)* scale;

				if (currentAngle >= 0 && currentAngle < 90) {
					labelX = centerX + axisX;
					labelY = centerY - axisY;
				} else if (currentAngle < 180) {
					labelX = centerX - axisX;
					labelY = centerY - axisY;
				} else if (currentAngle < 270) {
					labelX = centerX - axisX;
					labelY = centerY + axisY;
				} else {
					labelX = centerX + axisX;
					labelY = centerY + axisY;
				}
				
				LineMetrics lm = getLabelFont().getLineMetrics(label,
						fontRenderContext);
				double ascent = lm.getAscent();

				/**
				 * set the gap between the label and axis, or between the label
				 * and the center point.
				 */
				if (Math.abs(labelX - rectangle2D.getCenterX()) < LABELANDCENTERGAP) {
					labelX += LABELANDAXISGAP;
					labelY += ascent / (float) 2;
				} else if (Math.abs(labelY - rectangle2D.getCenterY()) < LABELANDCENTERGAP) {
					labelY += LABELANDAXISGAP;
				} else if (labelX >= rectangle2D.getCenterX()) {
					if (labelY < rectangle2D.getCenterY()) {
						labelX += LABELANDAXISGAP;
						labelY += LABELANDAXISGAP;
					} else {
						labelX -= LABELANDAXISGAP;
						labelY += LABELANDAXISGAP;
					}
				} else {
					if (labelY > rectangle2D.getCenterY()) {
						labelX -= LABELANDAXISGAP;
						labelY -= LABELANDAXISGAP;
					} else {
						labelX += LABELANDAXISGAP;
						labelY -= LABELANDAXISGAP;
					}
				}
				//set label font
				HashMap<TextAttribute, Comparable<?>> hm = new HashMap<TextAttribute, Comparable<?>>();
				hm.put(TextAttribute.SIZE, 14); 
				hm.put(TextAttribute.FAMILY,"Impact");//
				Font font = new Font(hm);

				graphics2D.setPaint(Color.blue);
				graphics2D.setFont(font);
				graphics2D.drawString(label, (float) labelX, (float) labelY);
			}
		}
	}
}

以上java代码就完成了,页面也很简单:

<%@ page contentType="text/html;charset=gb2312" pageEncoding="GB2312"%>
<%@ page import="com.bleum.test.ok.*"%>
<%@ page import="java.io.PrintWriter"%>
<%
	CreateChart createChart = new CreateChart();
	String fileName = createChart.getSpiderChart(session,
			new PrintWriter(out));
	String graphURL = request.getContextPath()
			+ "/servlet/DisplayChart?filename=" + fileName;
%>
<html>
<head>
<title>JFreeChart使用例子</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body>
<img src="<%=graphURL%>" width=500 height=300 border=0
	usemap="<%=fileName%>">
</body>
</html>

不过要注意这里的servlet是JFreeChart已经封装好的一个类:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>test222</display-name>
  <welcome-file-list>
    <welcome-file>mychart.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>DisplayChart</servlet-name>
    <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>DisplayChart</servlet-name>
    <url-pattern>/servlet/DisplayChart</url-pattern>
  </servlet-mapping>
</web-app>