ORDS, SODA & JSON in the Database

In ORDS 3.0 (without APEX) I've successfully created POST and PUT handlers that use X-APEX-FORWARD to redirect to the newly created or updated resource's URL.  I've tried the same with a GET handler, source type of 'plsql/block' but have not been able to get it to work.  Specifically I'm trying to implement a query at a base URL that will derive a URL, then set the X-APEX-FORWARD response header value to that derived URL and  trigger a redirect.

E.g. I want to issue a GET request with the following URL - https://<server>:<port>/ords/x/y/qry/?inv_number=123456

The URL returned should point to the account number this invoice applies to (as an example).

For demonstration purposes I have defined templates, handlers and parameters as follows:

begin

   ords.define_template(p_module_name => 'y'

                       ,p_pattern     => 'qry/'

                       ,p_comments    => '');

   ords.define_handler(p_module_name    => 'y'

                      ,p_pattern        => 'qry/'

                      ,p_method         => 'GET'

                      ,p_source_type    => 'plsql/block'

                      ,p_source         =>

'begin

   if :inv_number is not null then

      for rec in (select utl_url.escape(''../accs/i.account_number||''/'') account_url

                    from invoices i

                   where i.invoice_number = :inv_number)

      loop

         :location := rec.open_invoices_url;

         :status := 302;

      end loop;

   else

      htp.p(''...'');

      :status := 200;

   end if;

end;

'

                      ,p_items_per_page => 25);

   ords.define_parameter(p_module_name         => 'y'

                        ,p_pattern            => 'qry/'

                        ,p_method              => 'GET'

                        ,p_name                => 'X-APEX-FORWARD'

                        ,p_bind_variable_name  => 'location'

                        ,p_source_type         => 'HEADER'

                        ,p_param_type          => 'STRING'

                        ,p_access_method       => 'OUT'

   );

   ords.define_parameter(p_module_name         => 'y'

                        ,p_pattern             => 'qry/'

                        ,p_method              => 'GET'

                        ,p_name                => 'X-APEX-STATUS-CODE'

                        ,p_bind_variable_name  => 'status'

                        ,p_source_type         => 'HEADER'

                        ,p_param_type          => 'INT'

                        ,p_access_method       => 'OUT'

   );

   commit;

end;

I'm not sure what is materially different here from what I am doing in my POST and PUT requests, but this invocation will not return anything.  If I put an htp.p() expression within the loop to display the selected value, this shows when called by a client, so the problem is not with the data.

Any help on this greatly appreciated.

Regards,

Ryan.