用JfreeChart画散点图，查看JfreeChart的Demo，写的都挺复杂的，关键是Demo中把简单的事情复杂化了，比如展示的例子是一个正弦曲线什么的，让初次画散点图的我们摸不着头脑。关键是他们得到数据集搞得太过复杂，后来想明白了，不就是二维数组嘛。想通了这一点，一切问题都解决了，不过，对于我们项目的特殊要求，并不是只画几个点那么简单，还要加上区域范围与文字说明，在查看文档及自己摸索下，2天时间，终于搞定。下面分享一下成果，呵，还是有点成就感的。

 首先，看画图的API，参数有：

ChartFactory.createScatterPlot（），其中，有一个xydataset，那么，我们先要知道这个xydataset是什么结构的，再看所需xydataset，散点图，也就是单独画出点，也就是一个二维数据了，x ，y坐标嘛！

那么，先做好准备工作，第一步，拿数据，这就不用啰嗦了，就是得到一个List也好，Set也行。

第二步，加载到数据集：

/**
 * 
 * @param xydatalist
 * @param bloods
 * @return
 */
	public static XYDataset createxydataset(List<PressureBean> xydatalist,
			String bloods) {
		DefaultXYDataset xydataset = new DefaultXYDataset();

		int size = xydatalist.size();
		double[][] datas = new double[2][size];
		for (int i = 0; i < size; i++) {
			PressureBean pres = xydatalist.get(i);
			int sys = pres.getSyspress();//收缩压
			int dia = pres.getDiapress();//舒张压

			datas[0][i] = sys;
			datas[1][i] = dia;
		}

		xydataset.addSeries(bloods, datas);

		return xydataset;

	}

下一步，另外一个准备工作，画图方法：

public static JFreeChart createChart(XYDataset xydataset,
			String bloodcattile, String shou, String shu, String nobloodData,
			String bloods, String nomal, String fore, String one, String two,
			List<PressureBean> list, Log log) {

		// 有可能用户在后面的版本中故意输入不正常数值，但是为了保证图片画图的完整，这里先计算
		// 用户血压值的最大值。
		int maxpress = 160;
		int addmax = 20;

		if (list != null && list.size() > 0) {

			Iterator<PressureBean> it = list.iterator();
			while (it.hasNext()) {
				PressureBean pres = it.next();
				
				if (maxpress < pres.getDiapress()) {
					maxpress = pres.getDiapress();
				}

				if (maxpress < pres.getSyspress()) {
					maxpress = pres.getSyspress();
				}
			}

			maxpress += addmax;


			log.info("high press value is =" + maxpress);

		}

		JFreeChart jfreechart = ChartFactory.createScatterPlot(bloodcattile,
				shou, shu, xydataset, PlotOrientation.VERTICAL, true, false,
				false);
		jfreechart.setBackgroundPaint(Color.white);
		jfreechart.setBorderPaint(Color.GREEN);
		jfreechart.setBorderStroke(new BasicStroke(1.5f));
		XYPlot xyplot = (XYPlot) jfreechart.getPlot();
		xyplot.setNoDataMessage(nobloodData);
		xyplot.setNoDataMessageFont(new Font("", Font.BOLD, 14));
		xyplot.setNoDataMessagePaint(new Color(87, 149, 117));

		xyplot.setBackgroundPaint(new Color(255, 253, 246));
		ValueAxis vaaxis = xyplot.getDomainAxis();
		vaaxis.setAxisLineStroke(new BasicStroke(1.5f));

		ValueAxis va = xyplot.getDomainAxis(0);
		va.setAxisLineStroke(new BasicStroke(1.5f));

		va.setAxisLineStroke(new BasicStroke(1.5f)); // 坐标轴粗细
		va.setAxisLinePaint(new Color(215, 215, 215)); // 坐标轴颜色
		xyplot.setOutlineStroke(new BasicStroke(1.5f)); // 边框粗细
		va.setLabelPaint(new Color(10, 10, 10)); // 坐标轴标题颜色
		va.setTickLabelPaint(new Color(102, 102, 102)); // 坐标轴标尺值颜色
		ValueAxis axis = xyplot.getRangeAxis();
		axis.setAxisLineStroke(new BasicStroke(1.5f));

		XYLineAndShapeRenderer xylineandshaperenderer = (XYLineAndShapeRenderer) xyplot
				.getRenderer();
		xylineandshaperenderer.setSeriesOutlinePaint(0, Color.WHITE);
		xylineandshaperenderer.setUseOutlinePaint(true);
		NumberAxis numberaxis = (NumberAxis) xyplot.getDomainAxis();
		numberaxis.setAutoRangeIncludesZero(false);
		numberaxis.setTickMarkInsideLength(2.0F);
		numberaxis.setTickMarkOutsideLength(0.0F);
		numberaxis.setAxisLineStroke(new BasicStroke(1.5f));
		numberaxis.setUpperBound(maxpress);
		numberaxis.setLowerBound(60);//最小值设置为60
		NumberAxis numberaxis1 = (NumberAxis) xyplot.getRangeAxis();
		numberaxis1.setTickMarkInsideLength(2.0F);
		numberaxis1.setTickMarkOutsideLength(0.0F);
		numberaxis1.setUpperBound(105d);
		numberaxis1.setLowerBound(35);
		numberaxis1.setAxisLineStroke(new BasicStroke(1.5f));

		// if (xydataset != null) {
		XYBoxAnnotation box = new XYBoxAnnotation(0, 0, 89, 59); //正常血压所在区域内边界
		XYBoxAnnotation box1 = new XYBoxAnnotation(0, 0, 119, 79);//高血压前期所在区域内边界
		XYBoxAnnotation box2 = new XYBoxAnnotation(0, 0, 139, 89);//高血压一期所在区域内边界
		XYBoxAnnotation box3 = new XYBoxAnnotation(0, 0, 159, 99);//高血压二期所在区域内边界
		XYTextAnnotation text1 = new XYTextAnnotation(nomal, 70, 62.5);//标识“正常”
		XYTextAnnotation text = new XYTextAnnotation(fore, 70, 82.5);//“高血压前期”
		XYTextAnnotation text2 = new XYTextAnnotation(one, 70, 91.5);//“高血压一期”
		XYTextAnnotation text3 = new XYTextAnnotation(two, 70, 101.5);//“高血压二期”

		
		//将上面的边界线条，说明文字加入到xyplot中。
		xyplot.addAnnotation(box);
		xyplot.addAnnotation(box1);
		xyplot.addAnnotation(box2);
		xyplot.addAnnotation(box3);

		xyplot.addAnnotation(text);
		xyplot.addAnnotation(text1);
		xyplot.addAnnotation(text2);
		xyplot.addAnnotation(text3);
		// }
		return jfreechart;
	}

最后一步,返回图片URL

public static void drawScatterChart(IrisIoInterface io, Log log,
			XYDataset xydataSet, String title, String shou, String shu,
			String nodata, String boolds, String nomal, String fore,
			String one, String two, List<PressureBean> list) {

		JFreeChart chart = createChart(xydataSet, title, shou, shu, nodata,
				boolds, nomal, fore, one, two, list, log);

		HttpServletRequest request = io.getRequest();
		String filename = "";
		String graphURL = "";
		try {
			filename = ServletUtilities.saveChartAsPNG(chart, 400, 300, null,
					io.getSession());
			graphURL = request.getContextPath() + "/displayChart?filename="
					+ filename;
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			log.error(e);
		}

		io.setData("filename", filename, BeanShare.BEAN_SHARE_REQUEST);
		io.setData("scatterurl", graphURL, BeanShare.BEAN_SHARE_REQUEST);

	}

效果图：

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