JFreeChart 实例(原创)

用servlet生成图片，源码如下：

package com.test.chart;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import org.jfree.data.time.TimeSeries;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.time.Month;
import org.jfree.chart.axis.DateAxis;
import org.jfree.data.time.Minute;
import org.jfree.chart.ChartFactory;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.ChartUtilities;

public class ChartServlet extends HttpServlet {
      private static final String CONTENT_TYPE = "text/html; charset=GBK";

      //Initialize global variables
      public void init() throws ServletException {
      }

      // service
      public void service(HttpServletRequest request,
                          HttpServletResponse response) throws
              ServletException, IOException {
          OutputStream out = response.getOutputStream(); // 定义输出流
          try {
              JFreeChart chart = null; // 创建图标工具

              chart = createTimeSeriesChart(); // 产生折线图
              if (chart != null) {
                  response.setContentType("image/png"); // 定义类型
                  ChartUtilities.writeChartAsPNG(out, chart, 600, 300); // 输出
              }
          } catch (Exception e) {
              System.err.println(e.toString());
          } finally {
              out.close(); // 关闭流
          }

      }

      private JFreeChart createTimeSeriesChart() {

          TimeSeries series = new TimeSeries("实时状态图", Minute.class); // 第一条折线
          TimeSeries series2 = new TimeSeries("实时状态图2", Minute.class); // 第二条折线

          TimeSeriesCollection timeseriescollection = new TimeSeriesCollection(); // 定义折线集合

          timeseriescollection.addSeries(series); // 添加第一条曲线
          timeseriescollection.addSeries(series2); // 添加第二条曲线
//          Day day = new Day(1, Month.JANUARY, 2001); // 定义日期

          // Minute(int minute, int hour, int day, int month, int year)
          Minute current = new Minute(2, 14, 25, Month.JANUARY, 2007); // 图形使用的时间

          // 添加测试数据
          for (int i = 0; i < 50; i++) {
              series.add(current, Math.random() * 100); // 添加数据
              series2.add(current, Math.random() * 100);
              current = (Minute) current.next();
          }

          //XYDataset data = new TimeSeriesCollection(series);
          // 创建图形
          // createTimeSeriesChart(java.lang.String title, java.lang.String timeAxisLabel, java.lang.String valueAxisLabel, XYDataset dataset, boolean legend, boolean tooltips, boolean urls)
//      Parameters:
//title - the chart title (null permitted).
//timeAxisLabel - a label for the time axis (null permitted).
//valueAxisLabel - a label for the value axis (null permitted).
//dataset - the dataset for the chart (null permitted).
//legend - a flag specifying whether or not a legend is required.
//tooltips - configure chart to generate tool tips?
//urls - configure chart to generate URLs?

          JFreeChart chart = ChartFactory.createTimeSeriesChart(
                  "实时状态图",
                  "时间(分钟)",
                  "数值",
                  timeseriescollection,
                  true,
                  true,
                  false
                             );

          XYPlot xyplot = chart.getXYPlot();

//          valueaxis.setAutoRange(true); // 是否自动调整显示区域
//          valueaxis.setFixedAutoRange(60000000D); // 设置固定宽度
//          valueaxis.setAutoRangeMinimumSize( 300000D ); // 设置最小刻度
//          valueaxis.setLowerBound( 1179473079718D ); //最小显示的值

          DateAxis dateAxis = (DateAxis) xyplot.getDomainAxis();
          //      public Date(int year, int month, int date, int hrs, int min) {
//          year - 减 1900 的年份。
//month - 0-11 之间的月份。
//date - 一月中 1-31 之间的某一天。
//hrs - 0-23 之间的小时数。
//min - 0-59 之间的分钟数。
          Date dt = new Date(107, 0, 25, 14, 0);
          Date dts = new Date(107, 0, 25, 15, 0);
          // 横坐标设置
          dateAxis.setMaximumDate(dts); // 日期轴上的最小日期
          dateAxis.setMinimumDate(dt); // 日期轴上的最大日期
//          dateAxis.setAutoRange( true ); // 自动调整
          //dateAxis.setAutoRangeMinimumSize( 30000D );
          // AbstractRenderer
          //void setSeriesPaint(int series,Paint paint)指定分类图形的颜色
//          AbstractRenderer renderer = (AbstractRenderer)chart.getCategoryPlot().getRenderer();
//          Color c = new Color();
          //renderer.setSeriesPaint(1 , Color.BLUE );

          // 纵坐标设定
          ValueAxis valueaxis = null;
          valueaxis = xyplot.getRangeAxis();
          valueaxis.setRange(0.0D, 200D); // 高度范围为 0 - 200
//          xyplot.setDataset(1, timeseriescollection1);
          // xyplot.setRenderer(1,new DefaultXYItemRenderer());
          return chart;
      }

      //Clean up resources
      public void destroy() {
      }
}

新建网页index.html，源码如下 :

<html>
    <head>
    </head>
    <script type="text/javascript">
      var req;
      setInterval( "castVote()" , 3000 )
      function castVote1() {
          document.getElementById( "votes" ).innerHTML = "<IMG src='chartservlet' BORDER=1 WIDTH=600 HEIGHT=300/>"
      }
function castVote(rank) {
    // This demo uses simple Html/JS only, so we load a static html page
    var url = "ii.jsp";
    var callback = processAjaxResponse;
    executeXhr(callback, url);
}

function executeXhr(callback, url) {
    // branch for native XMLHttpRequest object
        if (window.XMLHttpRequest) {
            req = new XMLHttpRequest();
            req.onreadystatechange = callback;
            req.open("GET", url, true);
            req.send(null);
        } // branch for IE/Windows ActiveX version
        else if (window.ActiveXObject) {
            req = new ActiveXObject("Microsoft.XMLHTTP");
           if (req) {
                req.onreadystatechange = callback;
                req.open("GET", url, true);
                req.send();
            }
        }
}

    function processAjaxResponse() {
        // only if req shows "loaded"
        if (req.readyState == 4) {
            // only if "OK"
            if (req.status == 200) {
                document.getElementById('votes').innerHTML = req.responseText;
            } else {
                alert("There was a problem retrieving the XML data:/n" +
                   req.statusText);
            }
        }
}
    </script>
    <body>
      <div id="votes"><IMG src='chartservlet' BORDER=1 WIDTH=600 HEIGHT=300/></div>
    </body>
</html>
将web.xml添加如下内容：

    <servlet>
      <servlet-name>chartservlet</servlet-name>
      <servlet-class>com.test.chart.ChartServlet</servlet-class>
    </servlet>
    <servlet-mapping>
      <servlet-name>chartservlet</servlet-name>
      <url-pattern>/chartservlet</url-pattern>
    </servlet-mapping>