/**
  * Called when the selection changed in the tree. Loads the selected certificate.
  *
  * @param e the event
  */
 private void valueChangedPerformed(TreeSelectionEvent e) {
   Object o = e.getNewLeadSelectionPath().getLastPathComponent();
   if (o instanceof DefaultMutableTreeNode) {
     DefaultMutableTreeNode node = (DefaultMutableTreeNode) o;
     infoTextPane.setText(toString(node.getUserObject()));
   }
 }