Memanggil Laporan Berparameter dengan jButton (NetBeans)

 private void jButton_bulananActionPerformed(java.awt.event.ActionEvent evt) {                                               
        // TODO add your handling code here:
        try {
            String nmFile = "D:/Java_Produksi/lap_bulanan_produksi.jasper";
            sambung_db();
            HashMap hash = new HashMap(2);
            hash.put("id_karyawan",jComboBox_id_Jaryawan.getSelectedItem());
            hash.put("tahun",jComboBox_tahun.getSelectedItem());
            hash.put("bulan",jComboBox_bulan.getSelectedItem());
            File file=new File(nmFile);
            JasperReport jasperReport=(JasperReport)JRLoader.loadObject(file.getPath());
            JasperPrint jasperPrint=JasperFillManager.fillReport(jasperReport,hash,conn);
            JasperViewer.viewReport(jasperPrint,false);
            JasperViewer.setDefaultLookAndFeelDecorated(true);
        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, "Laporan Tidak Dapat Dicetak !\n" +
                e.getMessage(), "Cetak Laporan", JOptionPane.ERROR_MESSAGE);
        }
    }