public void setIdentity(String id) {
    String new_ident=null;
    char [] c = {'\0'};
    String endtag = new String(c);
    if (id.endsWith(endtag)) {
      new_ident = new String (id.substring(0,id.length()-1) +"\\"+ "0");
    } else {
      new_ident=id;
    }
    
    try {
      Node n = this.documentRoot.getElementsByTagName("IDENTIDAD_PRINCIPAL").
          item(0);
      try {
        n.getFirstChild().setNodeValue(new_ident);
      }
      catch (Exception e) {
        // no hay datos, hay que crear el nodo de datos
        n.appendChild(documentRoot.createTextNode(id));
      }

      AlmacenIdentidades.getInstance().reloadConfiguration();
    }
    catch (Exception e) {
      logger.severe(
          "Error trying to set the tag IDENTIDAD_PRINCIPAL in the config file: " +
          e.getMessage());
      JOptionPane.showMessageDialog(null,
                                    "Error trying to set the tag IDENTIDAD_PRINCIPAL in the config file",
                                    "FATAL ERROR", JOptionPane.ERROR_MESSAGE);
      System.exit( -1);
    }
  }