/**
   * File upload listener
   *
   * @param event
   * @throws Exception
   */
  public void listener(FileUploadEvent event) throws Exception {
    UploadedFile file = event.getUploadedFile();

    try {

      DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
      DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
      Document doc = dBuilder.parse(file.getInputStream());
      doc.getDocumentElement().normalize();

      processUsers(doc.getElementsByTagName("users"));
      processAuthors(doc.getElementsByTagName("authors"));
      processPublishers(doc.getElementsByTagName("publishers"));
      processGenres(doc.getElementsByTagName("genres"));
      processBooks(doc.getElementsByTagName("books"));
      processExemplars(doc.getElementsByTagName("exemplars"));
      processBookings(doc.getElementsByTagName("bookings"));
      processBorrows(doc.getElementsByTagName("borrows"));

      userMgr.flush();
      bookMgr.flush();
      authorMgr.flush();
      bookingMgr.flush();
      exemplarMgr.flush();
      genreMgr.flush();
      publisherMgr.flush();
      borrowMgr.flush();

      userMgr.clear();
      bookMgr.clear();
      authorMgr.clear();
      bookingMgr.clear();
      exemplarMgr.clear();
      genreMgr.clear();
      publisherMgr.clear();
      borrowMgr.clear();

    } catch (Exception e) {
      FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Import se nezdařil."));
      e.printStackTrace(System.out);

      return;
    }

    FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Import proběhl úspěšně."));
  }