}
private void enforceOwnershipConstraint(Action aAction, RequestParser aRequestParser) throws AppException, BadRequestException {
if (aAction instanceof FetchIdentifierOwner ) {
FetchIdentifierOwner constraint = (FetchIdentifierOwner)aAction;
Id owner = constraint.fetchOwner();
String ownerText = (owner == null ? null : owner.getRawString());
HttpSession session = aRequestParser.getRequest().getSession(DO_NOT_CREATE_SESSION);
if( session == null ) {
ownershipConstraintNotImplementedCorrectly(OWNERSHIP_NO_SESSION);
}