Reporting errors or exceptions back to the caller

Question

I'm u sing OracleAS 10.1.3 and I'm exposing some of my PL/SQL procedures as web services. I was wondering what the convention is for reporting errors back to the caller. I read a little bit about Soap faults and some lack of support in the current JDev release.
Are soap faults the standard way of reporting handled exceptions? What about returning a record like:
   type r_ws_response_string is record (
      result          varchar2 (4000),
      return_code     number,
      error_message   varchar2 (4000)
   );... and having the caller check the return_code. Bad idea?
Any resources you can point is is appreciated (books/sites).
-Vahid Pazirandeh

Answer 1

Hi Toby,
Yes, I've come up with a working solution.
Essentially, I've made use of PL/SQL's OUT parameters and always reporting a status to the caller. At minimum, any procedure or function that I expose as a web service will have two out parameters: status, error_msg. The benefit of having a status being returned is that the caller can build logic based on different problems encountered, rather than just saying "an error occured". The error strings that you define are textual error codes, so they shouldn't change once you decide on an API.
The caller will always check for the value of status, if it is not 'SUCCESSFUL', then something is wrong. They can then log the value of error_msg so that their developers can figure out what went wrong later.
What's also nice is that the XML that's generated by JDeveloper looks clean when we're using one or more OUT params.
I don't know what the best way is to deal with this problem, but this works for me. :) Here's an example:
g_status_success        := 'SUCCESSFUL';
g_status_bad_password   := 'ERROR_INVALID_PASSWORD';
g_status_file_not_found := 'ERROR_FILE_NOT_FOUND';
g_status_unknown_error  := 'ERROR_UNKNOWN_EXCEPTION';
procedure give_me_file(password varchar2,
                       status out varchar2,
                       error_msg out varchar2,
                       file out blob)
is
begin
     if bad_password(password) then
          status := g_status_bad_password;
          error_msg := 'You entered the wrong password friend!';
          return;
     end if;
     file := get_top_secret();
     if file is null then
          status := g_file_not_found;
          error_msg := 'Your file could not be found';
          return;
     end if;
     status := g_status_success;
     exception
          when others then
               status := g_status_unknown_error;
               error_msg := 'An unknown error occured.  Please file a ticket.';
end;Regards,
Vahid Pazirandeh