@RequestMapping(value = "/children")
  @ResponseBody
  public List<?> children(@RequestParam(value = "id") Long id) {
    PermissionTarget permissionTarget = new PermissionTarget();
    permissionTarget.setId(id);

    return userGroupTreeService.getChildren(permissionTarget);
  }
 @RequestMapping(value = "/roots")
 @ResponseBody
 public List<?> roots() {
   return userGroupTreeService.getPermissionRoots();
 }