最近由于项目需要，开始学习JFreeChart和iText，在网上找了一下相关的资料不是很多，特别是JFreeChart在官方文档上没有像iText那样详尽的说明及例子，而且官方的demo只有一个jar文件，里面也比较乱，不知道从什么地方下手，在网上找了几个例子，开始循序渐进的学吧！

第一个例子是个台湾人写的，很多的名词都是用的台湾说法，读过侯捷先生翻译的书的朋友应该有很深的体会！学习任何一个开源的项目第一个任务就是配环境，

JFreeChart 首頁：http://www.jfree.org/jfreechart/

JFreeChart API：http://www.jfree.org/jfreechart/javadoc/

目前的版本：jfreechart-1.0.0具体的安装和classpath的配置就不多说了



上面就是该例子要生成的柱状图！代码如下：

package HelloJChart;import java.awt.Dimension;

import javax.swing.JFrame;

import org.jfree.chart.ChartFactory;import org.jfree.chart.ChartPanel;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 HelloBarChart extends JFrame{ public HelloBarChart(){ CategoryDataset dataset = createDataset(); JFreeChart chart = createChart(dataset); chart = customizeChart(chart); ChartPanel chartPanel = new ChartPanel(chart); chartPanel.setPreferredSize(new Dimension(500, 270)); getContentPane().add(chartPanel);

pack(); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); }

public static void main(String[] args){ new HelloBarChart(); }

private CategoryDataset createDataset(){ // row keys... String series1 = "First"; String series2 = "Second"; String series3 = "Third";

// column keys... String category1 = "Category 1"; String category2 = "Category 2"; String category3 = "Category 3"; String category4 = "Category 4"; String category5 = "Category 5";

// create the dataset... DefaultCategoryDataset dataset = new DefaultCategoryDataset();

dataset.addValue(1.5, series1, category1); dataset.addValue(4.2, series1, category2); dataset.addValue(3.0, series1, category3); dataset.addValue(5.0, series1, category4); dataset.addValue(5.0, series1, category5);

dataset.addValue(5.5, series2, category1); dataset.addValue(7.8, series2, category2); dataset.addValue(6.0, series2, category3); dataset.addValue(8.0, series2, category4); dataset.addValue(4.0, series2, category5);

dataset.addValue(4.0, series3, category1); dataset.addValue(3.0, series3, category2); dataset.addValue(2.0, series3, category3); dataset.addValue(3.0, series3, category4); dataset.addValue(6.0, series3, category5);

return dataset; }

private JFreeChart createChart(final CategoryDataset dataset){ JFreeChart chart = ChartFactory.createBarChart( "Hello Bar Chart", // chart title "Category", // domain axis label "Value", // range axis label dataset, // data PlotOrientation.VERTICAL, // orientation true, // include legend true, // tooltips? false // URLs? ); return chart; }

private JFreeChart customizeChart(final JFreeChart chart){ return chart; }}

要建立一個JFreeChart的圖形主要有三個步驟
建立一個擁有資料的DataSet 用DataSet創造JFreeChart 對JFreeChart作一些自訂的設計 顯示JFreeChart
第一步：建立DataSet

BarChart使用的DataSet接口org.jfree.data.CategoryDataset的DataSet。有兩種方式來建立CategoryDataSet
使用CategoryDataSet的子类org.jfree.data.DefaultCategoryDataset，再用addValue()把資料加入DataSet中 建立包含數值的二維陣列，再使用org.jfree.data.DatasetUtilities的createCategoryDataset()
使用DefaultCategoryDataSet

DefaultCategoryDataSet class:

public void addValue(double value, java.lang.Comparable rowKey, java.lang.Comparable columnKey)public void addValue(java.lang.Number value, java.lang.Comparable rowKey, java.lang.Comparable columnKey)

value - the valuerowKey - the row keycolumnKey - the column key

参照前面的createDataset方法！

使用org.jfree.data.DatasetUtilities

org.jfree.data.DatasetUtilities class:

public static CategoryDataset createCategoryDataset(String rowKeyPrefix, String columnKeyPrefix, java.lang.Number[][] data)public static CategoryDataset createCategoryDataset(String[] rowKeys, String[] columnKeys, double[][] data)public static CategoryDataset createCategoryDataset(String rowKey, KeyedValues rowData)

rowKeyPrefix - the row key prefix.columnKeyPrefix - the column key prefix.rowKeys - the row keys.columnKeys - the column keys.data - the data.



private CategoryDataset createDataset(){ double[][] data = new double[][]{{1.0, 43.0, 35.0, 58.0, 54.0, 77.0, 71.0, 89.0} , {54.0, 75.0, 63.0, 83.0, 43.0, 46.0, 27.0, 13.0} , {41.0, 33.0, 22.0, 34.0, 62.0, 32.0, 42.0, 34.0} }; return DatasetUtilities.createCategoryDataset("Series ", "Factor ", data); }

第二步：創造JFreeChart

要用DataSet創造出一個JFreeChart類別，我們並不直接實體化出一個JFreeChart實體，而是使用ChartFactory類別裡面的方法。

ChartFactory class:

public static JFreeChart createBarChart(java.lang.String title, java.lang.String categoryAxisLabel, java.lang.String valueAxisLabel, CategoryDataset data, PlotOrientation orientation, boolean legend, boolean tooltips, boolean urls)

title - the chart title.categoryAxisLabel - the label for the category axis.valueAxisLabel - the label for the value axis data - the dataset for the chart.orientation - the plot orientation (PlotOrientation.HORIZONTAL or PlotOrientation.VERTICAL).legend - a flag specifying whether or not a legend is required.tooltips - configure chart to generate tool tips?urls - configure chart to generate URLs?



private JFreeCha