.jasper report return null values

Hello,

I am trying to display the .jasper report in the browser.
I am doing by the following code.

It loads the report into the browser but only show the static text. It did not print the values from the database, instead prints "null"

While in .jrxml file it shows the every thing properly.. Any Help...

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.HashMap;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.jasperreports.engine.JREmptyDataSource;
import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JasperRunManager;

public class JasperReportsBrowserDemoServlet extends HttpServlet
{

protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException
  {
    ServletOutputStream servletOutputStream = response.getOutputStream();
    File reportFile = new File(getServletConfig().getServletContext()
        .getRealPath("/reports/Simple_Report.jasper"));
    byte[] bytes = null;

try
    {
      bytes = JasperRunManager.runReportToPdf(reportFile.getPath(),
          new HashMap(), new JREmptyDataSource());

response.setContentType("application/pdf");
      response.setContentLength(bytes.length);

servletOutputStream.write(bytes, 0, bytes.length);
      servletOutputStream.flush();
      servletOutputStream.close();
    }
    catch (JRException e)
    {
      // display stack trace in the browser
      StringWriter stringWriter = new StringWriter();
      PrintWriter printWriter = new PrintWriter(stringWriter);
      e.printStackTrace(printWriter);
      response.setContentType("text/plain");
      response.getOutputStream().print(stringWriter.toString());
    }
  }
}

Any help...