Report Application Series-Chart Jfreechart: 2nd Chapter Column Chart

2.1. Simple Bar Chart

First prepare the data for the histogram, the histogram must use Categorydataset, here we use Defaultcategorydataset.

DefaultCategoryDataset　dataset　=　new　DefaultCategoryDataset();
dataset.addValue(100,"Spring　Security","Jan");
dataset.addValue(200,"jBPM　4","Jan");
dataset.addValue(300,"Ext　JS","Jan");
dataset.addValue(400,"JFreeChart","Jan");

Each call to AddValue () adds a piece of data to the dataset, which appears to be a columnar rectangle, the first parameter 100 is the length of the column rectangle, the second parameter represents the name of the data, and the third parameter represents the classification of the data.

With the chart data, the next step is to create a columnar chart with this data.

JFreeChart　chart　=　ChartFactory.createBarChart(
　　 "chart",//　标题
　　 "num",//　横轴名称
　　 "type",//　纵轴名称
　　 dataset,//　数据
　　 PlotOrientation.VERTICAL,//　使用垂直柱状图
　　 true,//　是否使用legend　
　　 false,//　是否使用tooltip　
　　 false　//　是否使用url链接
);

Finally, use Chartutilities to export chart as a PNG picture.

FileOutputStream　fos　=　null;

try　{
　　 fos　=　new　FileOutputStream("target/bar1.png");
　　 ChartUtilities.writeChartAsPNG(fos,chart,400,300);
}　finally　{
　　 fos.close();
}

Figure 2.1. Simple bar Chart