package ventana;
import java.awt.Frame;
import org.jfree.data.*;
import org.jfree.chart.*;
import org.jfree.chart.plot.*;
import java.awt.image.*;
import org.jfree.data.category.CategoryDataset;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.data.jdbc.JDBCCategoryDataset;
import org.jfree.data.jdbc.JDBCXYDataset;
import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;
import java.sql.*;
 
 
/**
 *
 * @author  Administrador
 */
public class VentanaGrafica extends java.awt.Frame {
    BufferedImage grafica = null;
    static BufferedImage image;
 
    /** Creates new form VentanaGrafica */
    public VentanaGrafica() {
       super("Ejemplos usando JFreeChart.");
        initComponents();
    }
 
 
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">                          
    private void initComponents() {
 
        addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                exitForm(evt);
            }
        });
 
        pack();
    }
    // </editor-fold>                        
 
    /** Exit the Application */
    private void exitForm(java.awt.event.WindowEvent evt) {                          
       System.exit(1);
 
    }                         
 
 
    // Variables declaration - do not modify                     
    // End of variables declaration                   
    public static BufferedImage creaImagen(Connection con) {
 
        try{
             String sql= "Select x as meses, y as ventas from sesiones";
            JDBCXYDataset xyDataset = new JDBCXYDataset(con,sql);
             JFreeChart chart = ChartFactory.createLineChart("Grafica de Ventas",
                "Meses","Ventas %",(CategoryDataset) xyDataset,PlotOrientation.VERTICAL,
                true,
                true,
                 true                // Show legend
                );
            //JFreeChart chart1 = ChartFactory.
                image = chart.createBufferedImage(600,400);
            return image;
        }catch(SQLException e){
            System.err.println("Error al obtener datos de la BDD: "+e);
        }
        return image;
    }
   public void paint(java.awt.Graphics g) {
 
        if(grafica == null) {
            grafica = this.creaImagen(Conexion.con);
        }
        g.drawImage(grafica,40,80,null);
    }
 
 
}
 
 

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: org.jfree.data.jdbc.JDBCXYDataset cannot be cast to org.jfree.data.category.CategoryDataset
        at ventana.VentanaGrafica.creaImagen(VentanaGrafica.java:65)
        at ventana.VentanaGrafica.paint(VentanaGrafica.java:82)
        at sun.awt.RepaintArea.paintComponent(RepaintArea.java:248)
        at sun.awt.X11.XRepaintArea.paintComponent(XRepaintArea.java:56)
        at sun.awt.RepaintArea.paint(RepaintArea.java:224)
        at sun.awt.X11.XComponentPeer.handleEvent(XComponentPeer.java:688)
        at java.awt.Component.dispatchEventImpl(Component.java:4706)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Java Result: 1
GENERACIÓN CORRECTA (total time: 29 seconds)