code: protected void beforeUpdate(ModeledAuthenticatedUser user,
              InternalType object, ModelType model) throws GuacamoleException {
  
          // By default, do nothing.
          if (!hasObjectPermission(user, model.getIdentifier(), ObjectPermission.Type.UPDATE))
              throw new GuacamoleSecurityException("Permission denied.");
  
      }
docs: Called before any object is updated through this directory object
  service. This function serves as a final point of validation before
  the update operation occurs. In its default implementation,
  beforeUpdate() performs basic permissions checks.
  
  @param user
  The user updating the existing object.
  
  @param object
  The object being updated.
  
  @param model
  The model of the object being updated.
  
  @throws GuacamoleException
  If the object is invalid, or an error prevents validating the given
  object.