display jfreecharts using servlets

I have a scenario where I need to display charts(generated using jfreecharts) converted it into a 开发者_开发技巧png image and then display them using servlets.

When the chart code extends either ApplicationFrame or Jframe I see the following exception when I display it using servlets :

java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
at java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:159)
at java.awt.Window.(Window.java:317)
at java.awt.Frame.(Frame.java:419)
at javax.swing.JFrame.(JFrame.java:194)

I read through a couple of places and this seems to be because of the ApplicationFrame and JFrame would cause this error.

If i pass just the chart object this throws a

java.lang.IllegalArgumentException: Null 'chart' argument.
    org.jfree.chart.ChartUtilities.writeChartAsPNG(ChartUtilities.java:181)
    org.jfree.chart.ChartUtilities.writeChartAsPNG(ChartUtilities.java:136)

Is there any solution for this?

ChartUtilities is the right choice; streams are supported, too. One approach requires Using Headless Mode in the Java SE Platform, but I've also gotten it to work with VNC.

Addendum: here's a related forum thread.

I will explain you in simple way as I faced the same problem as i was new.

Steps

1. Create a servlet
2. In doPost create outputstream
3. set content type to text/png
4. Create datasets
5. set values to dataset
6. create instance of jfreechart and call createchart(the chart you wanna use) using ChartFqactory.
7. finally call WriteChartAsPNG using ChartUtilities and pass the Jfreechart instance,outputstream,width,height.

DONE:

Sample below

 package polo;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartUtilities;
import org.jfree.chart.JFreeChart;
import org.jfree.data.general.DefaultPieDataset;


/**
 * Servlet implementation class PieChartDemo1Serv
 */
public class PieServ extends HttpServlet implements useme {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public PieServ() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    doPost(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub

        response.setContentType("image/png");   

        ServletOutputStream out = response.getOutputStream();

        DefaultPieDataset pieDataset = new DefaultPieDataset();

        pieDataset.setValue("In-Network ", .80);

        pieDataset.setValue("Out-of-Network ", .20);



        JFreeChart chart = ChartFactory.createPieChart("", pieDataset, true, true, false);

ChartUtilities.writeChartAsPNG(out, chart, 202, 182);
    System.out.println("done23");

    }


}

Now I know you what further.Study Pieplots/Legends to setup border and formatting.You can do a lot further.