Jfree bar chart servlet code with oracle database - oracle

Question

I am new to jfree chart I have the following code it runs without any error, however the browser shows me an empty page .. do not know where is the problem.
I am trying to create a bar chart using jfree chart in servlet and the data will be retrieved from oracle data base.
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.io.IOException;
import java.io.OutputStream;
import javax.servlet.ServletException;
import org.jfree.data.category.DefaultCategoryDataset;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.ChartUtilities;
public class BarChar extends HttpServlet {
#Override
public void init() {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
System.out.println("JDBC driver loaded");
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
}
}
#Override
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
OutputStream out = response.getOutputStream();
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn = DriverManager.getConnection("jdbc:oracle:thin:#localhost:1521:XE","FATIMAH", "FATIMAH");
DefaultCategoryDataset bar = new DefaultCategoryDataset();
Statement stmt = conn.createStatement();
ResultSet r = stmt.executeQuery("select category,marks from chart_data");
while (r.next())
{
String category = r.getString("CATEGORY");
int marks = r.getInt("MARKS");
bar.addValue(marks,"Mark",category);
}
JFreeChart BarChartObject=ChartFactory.createBarChart("Subject Vs Marks Bar Chart","Subject","Marks",bar,PlotOrientation.VERTICAL,true,true,false);
response.setContentType("image/png");
ChartUtilities.writeChartAsPNG(out, BarChartObject, 400, 300);
}
catch (Exception e) {
System.err.println(e.toString());
}
finally {
out.close();
}
}
}