docs: private void doImport() {
  		if (checkExistingCertificate()) {
  			// prevent overwriting
  			return;
  		}
  		final JFileChooser fc = new JFileChooser(System.getProperty("user.home"));
  		fc.setFileSelectionMode(JFileChooser.FILES_ONLY);
  		fc.setMultiSelectionEnabled(false);
  		fc.setSelectedFile(new File(CONFIGURATION_FILENAME));
  		fc.setFileFilter(new FileFilter() {
  			@Override
  			public String getDescription() {
  				// config.xml or *.pem files
  				return Constant.messages.getString("dynssl.filter.file");
  			}
  			@Override
  			public boolean accept(File f) {
  				String lcFileName = f.getName().toLowerCase(Locale.ROOT);
  				return lcFileName.endsWith(CONFIGURATION_FILENAME) || lcFileName.endsWith("pem") || f.isDirectory();
  			}
  		});
  		final int result = fc.showOpenDialog(this);
  		final File f = fc.getSelectedFile();
  		if (result == JFileChooser.APPROVE_OPTION && f.exists()) {
  			if (logger.isInfoEnabled()) {
  				logger.info("Loading Root CA certificate from " + f);
  			}
  			KeyStore ks = null;
  			if (f.getName().toLowerCase().endsWith("pem")) {
  				ks = convertPemFileToKeyStore(f.toPath());
  			} else {
  				try {
  					final ZapXmlConfiguration conf = new ZapXmlConfiguration(f);
  					final String rootcastr = conf.getString(DynSSLParam.PARAM_ROOT_CA);
  					if (rootcastr == null || rootcastr.isEmpty()) {
  						JOptionPane.showMessageDialog(
  								this,
  								Constant.messages.getString("dynssl.message.nocertinconf"),
  								Constant.messages.getString("dynssl.message.nocertinconf.title"),
  								JOptionPane.ERROR_MESSAGE);
  						return;
  					}
  
  					ks = SslCertificateUtils.string2Keystore(rootcastr);
  				} catch (final Exception e) {
  					logger.error("Error importing Root CA cert from config file:", e);
  					JOptionPane.showMessageDialog(this,
  							Constant.messages.getString("dynssl.message1.filecouldntloaded"),
  							Constant.messages.getString("dynssl.message1.title"),
  							JOptionPane.ERROR_MESSAGE);
  					return;
  				}
  			}
  			if (ks != null) {
  				setRootca(ks);
  			}
  
  		}
  	}