In the earlier tutorial I showed you how to create Bar chart using JFreeChart library. In this second article I’ll explain how to create pie chart. Everything is same like the previous tutorial, except the servlet code will be changed.
So let me first put the servlet code here:
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package com.cts.chartgen.servlets;
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import java.awt.Color;
import java.io.IOException;
import java.io.OutputStream;
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import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
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import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.data.general.DefaultPieDataset;
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public class PieChartGen extends HttpServlet {
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     public void doGet(HttpServletRequest req, HttpServletResponse resp)
           throws ServletException, IOException {
           genPieChart(req, resp);
     }
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     public void doPost(HttpServletRequest req, HttpServletResponse resp)
           throws ServletException, IOException {
           genPieChart(req, resp);
     }
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     public void genPieChart(HttpServletRequest req,
                             HttpServletResponse resp) {
           try {
                 OutputStream out = resp.getOutputStream();
                 // Create a simple Bar chart
                 DefaultPieDataset dataset = new DefaultPieDataset();
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                 dataset.setValue(“SCIENCE CLASS”, 65);
                 dataset.setValue(“ECONOMICS CLASS”, 25);
                 dataset.setValue(“LANGUAGE CLASS”, 10);
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                 JFreeChart chart =
                       ChartFactory.createPieChart(
                             “Students by Classes”,
                             dataset,
                             true,
                             true,
                             false);
                 chart.setBackgroundPaint(Color.white);
                 // Set the background colour of the chart
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                 resp.setContentType(“image/png”);
                 ChartUtilities.writeChartAsPNG(out, chart, 625, 500);
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           } catch (Exception e) {
                 System.err.println(
                       “Problem occurred while creating chart.” + e.getMessage());
           }
     }
}
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And the output is:
 
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Let me explain-
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An instance of DefaultPieDataset is created and this is populated with the statistical data. The data is set by invoking setValue() method.
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Now the createPieChart() method of ChartFactory is invoked which creates the actual pie chart object. The first argument is the name of the statement to be displayed, 2nd argument is the dataset itself, 3rd argument as true specifies if legends to be displayed, 4th argument holds true if we want to display tooltip and false as the 5th argument specifies if we need to place URL in the chart image.
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We set the background color of the chart as white. The default color is grey. This again can be customized.
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Next we generate the chart to be displayed using writeChartAsPNG() method of ChartUtilities class.
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Nice tutorial… I’m a newby… can you help me if instead of inserting the values directly… you colect the values from a txt file with this kind of layout…
error number, error description, values
Basicaly.. the program will perform a scan and when finding the error number.. it will collect the the value situated in the 2nd position…
thanks
Thanks for the tutorial. I came here because all my pie charts have a grey background and I can’t change it to white. I ran the code in this tutorial and unfortunately I still get the grey background unlike the screenshot you have.
Are any of you getting the same? Its really annoying!
Sorry for the post before I didn’t realize..
I said that it doesn’t work for me…it doesn’t reply anything
Maybe is because you don’t implement the getplot function???