Ciao sono anch'io alle prime armi con jasper report vi posto il mio listato di codice per ottenere un report utilizzando ireport per crearmi il file jrxml e poi una servlet che mi stampa il pdf.
Vi posto il mio codice:

stampa_report.java

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

import java.util.*;
import java.sql.*;

import net.sf.jasperreports.engine.*;
import net.sf.jasperreports.view.*;

public class stampa_report extends HttpServlet
{

protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException, SQLException, ClassNotFoundException, JRException
{
String reportSource = "./report/templates/template_report.jrxml";
String reportDest = "./report/results/report.pdf";

Map params = new HashMap();
response.setContentType("application/pdf");
try
{
JasperReport jasperReport = JasperCompileManager.compileReport(reportSource);

JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, params, new JREmptyDataSource());

JasperExportManager.exportReportToHtmlFile(jasperP rint, reportDest);

JasperViewer.viewReport(jasperPrint);
}
catch (JRException ex)
{
ex.printStackTrace();
}
}
}

la pagina jsp invece

<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>



<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>

<form name="Form1" action="stampa_report">
<input type="submit" value="Stampa Report" name="Bottone1" />
</form>

</body>
</html>