public void geraRelatorio() throws JRException, Exception
{

FacesContext context = FacesContext.getCurrentInstance();

HttpServletResponse response = (HttpServletResponse) context.getExternalContext().getResponse();

Connection con = getConnection( );
Statement stm = con.createStatement( );
String query = "SELECT * FROM PedidoOperadora ";
ResultSet rs = stm.executeQuery( query );

/* implementação da interface JRDataSource para DataSource ResultSet */
JRResultSetDataSource jrRS = new JRResultSetDataSource( rs );

/* HashMap de parametros utilizados no relatório. Sempre instanciados */
Map parameters = new HashMap();

JasperDesign desenho = JRXmlLoader.load( "C:/eclipse/workspace/telefonia/WebContent/relatorios/PedidoOperadora.jrxml" );

//compila o relatório
JasperReport relatorio = JasperCompileManager.compileReport( desenho );

JasperPrint impressao = JasperFillManager.fillReport( relatorio , parameters, jrRS );


JRXlsExporter exporter = new JRXlsExporter();
ByteArrayOutputStream xlsReport = new ByteArrayOutputStream();
exporter.setParameter(JRXlsExporterParameter.JASPER_PRINT, impressao);
exporter.setParameter(JRXlsExporterParameter.OUTPUT_STREAM, xlsReport);
exporter.setParameter(JRXlsExporterParameter.IS_REMOVE_EMPTY_SPACE_BETWEEN_ROWS, Boolean.TRUE);
exporter.setParameter(JRXlsExporterParameter.IS_WHITE_PAGE_BACKGROUND, Boolean.TRUE);
exporter.setParameter(JRXlsExporterParameter.IS_ONE_PAGE_PER_SHEET, Boolean.TRUE);
exporter.setParameter(JRXlsExporterParameter.OUTPUT_FILE_NAME, "c:/relatorio.xls");


exporter.exportReport();
byte[] bytes = xlsReport.toByteArray();
response.setContentType("application/vnd.ms-excel");
response.setContentLength(bytes.length);
xlsReport.close();
OutputStream ouputStream = response.getOutputStream();
ouputStream.write(bytes, 0, bytes.length);
ouputStream.flush();
ouputStream.close();

}

/* Realza contornan
iexão com o banco de dados, redo o objeto Connection */
private static Connection getConnection( ) throws
ClassNotFoundException, SQLException
{

String driver = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
String url = "jdbc:sqlserver://localhost:1433;databaseName=SGSCAMGBD";
String user = "user_adm";
String password = "admcamg";
Class.forName(driver);
Connection con = DriverManager.getConnection(url, user, password);
return con;
}