Swing/DisabledOkButtonOptionPane のバックアップ(No.2)

JPanel panel2 = new JPanel(new GridLayout(2, 1));
JTextField field2 = new JTextField();
Border enabledBorder = field2.getBorder();
Insets i = enabledBorder.getBorderInsets(field2);
Border disabledBorder = BorderFactory.createCompoundBorder(
    BorderFactory.createLineBorder(Color.RED),
    BorderFactory.createEmptyBorder(i.top - 1, i.left - 1, i.bottom - 1, i.right - 1));
String disabledMessage = "Text is required to create ...";
JLabel label2 = new JLabel(" ");
label2.setForeground(Color.RED);
panel2.add(field2);
panel2.add(label2);
if (field2.getText().isEmpty()) {
  field2.setBorder(disabledBorder);
  label2.setText(disabledMessage);
}
field2.addHierarchyListener(e -> {
  Component c = e.getComponent();
  if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0 && c.isShowing()) {
    EventQueue.invokeLater(c::requestFocusInWindow);
  }
});
field2.getDocument().addDocumentListener(new DocumentListener() {
  private void update() {
    boolean verified = !field2.getText().isEmpty();
    JButton b = field2.getRootPane().getDefaultButton();
    if (verified) {
      b.setEnabled(true);
      field2.setBorder(enabledBorder);
      label2.setText(" ");
    } else {
      b.setEnabled(false);
      field2.setBorder(disabledBorder);
      label2.setText(disabledMessage);
    }
  }

  @Override public void insertUpdate(DocumentEvent e) {
    update();
  }

  @Override public void removeUpdate(DocumentEvent e) {
    update();
  }

  @Override public void changedUpdate(DocumentEvent e) {
    update();
  }
});
JButton button2 = new JButton("show");
button2.addActionListener(e -> {
  Component p2 = log.getRootPane();
  EventQueue.invokeLater(() -> {
    JButton b = field2.getRootPane().getDefaultButton();
    if (b != null && field2.getText().isEmpty()) {
      b.setEnabled(false);
    }
  });
  int ret = JOptionPane.showConfirmDialog(
      p2, panel2, "Input text", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
  if (ret == JOptionPane.OK_OPTION) {
    log.setText(field2.getText());
  }
});