#1 2024-01-18 18:16:49

RaelB
Member
Registered: 2010-08-04
Posts: 57

Returning TServiceCustomStatus from interface method

Hi,

In SOA by Interfaces with custom HTTP Status you mention that TServiceCustomStatus was added and can be used as a return type for interface methods:

It won't change anything for mORMot client/server communication - just for non-mORMot HTTP clients, they will be able to check the HTTP response code.

So I have a method like this:

  INoteService = interface(IInvokable)
    ['{2B97D344-F806-4D6B-A3D9-56C61F9276BE}']
    ...
    function Delete(const NoteId: TID): TServiceCustomStatus;
  end;

  TNoteService = class(TInjectableObjectRest, INoteService)
  public
    ....
    function Delete(const NoteId: TID): TServiceCustomStatus;
  end;

function TNoteService.Delete(const NoteId: TID): TServiceCustomStatus;
begin
  Result := HTTP_NOCONTENT;
  Self.Server.Orm.Delete(TOrmNote, NoteId);
end;

If called from the mormot client: (vcl app)
NoteService.Delete(OrmNote.ID)

I get this error

Exception class EInterfaceFactory with message 'TInterfacedObjectFakeClient.FakeCall(INoteService.Delete) failed: 'Invalid returned JSON content: expects {result:...}, got ''. Process Project04InterfaceBasedClient.exe

If the delete method returns HTTP_SUCCESS, then there is no error.

I am doing this wrong?

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#2 2024-01-19 11:13:32

RaelB
Member
Registered: 2010-08-04
Posts: 57

Re: Returning TServiceCustomStatus from interface method

I did a bit more testing. The error occurs only with a return of HTTP_NOCONTENT. Other return values, such as HTTP_BADREQUEST, HTTP_FORBIDDEN don't cause a problem.

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#3 2024-01-19 14:19:40

ab
Administrator
From: France
Registered: 2010-06-21
Posts: 14,706
Website

Re: Returning TServiceCustomStatus from interface method

This is as expected.
HTTP_NOCONTENT means no content returned, i.e. no response body.
So if you force HTTP_NOCONTENT in your method, nothing is returned (body length = 0).
And our REST protocol REQUIRES something to be returned.
Therefore, it fails.

TServiceCustomStatus is meant for web clients, not for mORMot clients.
HTTP_NOCONTENT should never be set in methods. It is an internal implementation detail of HTTP.
If your method returns HTTP_SUCESS with no body, then the web server itself will return a HTTP_NOCONTENT. Don't assign this status code manually.

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#4 2024-01-19 15:38:30

RaelB
Member
Registered: 2010-08-04
Posts: 57

Re: Returning TServiceCustomStatus from interface method

I see, thanks for the info.

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#5 2024-01-19 16:39:36

ab
Administrator
From: France
Registered: 2010-06-21
Posts: 14,706
Website

Re: Returning TServiceCustomStatus from interface method

I have documented this behavior to be more explicit:
https://github.com/synopse/mORMot2/commit/3812dfb8

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#6 2024-01-20 23:34:05

RaelB
Member
Registered: 2010-08-04
Posts: 57

Re: Returning TServiceCustomStatus from interface method

ab wrote:

If your method returns HTTP_SUCCESS with no body, then the web server itself will return a HTTP_NOCONTENT.

So I take it you're referring to when the rsoHttp200WithNoBodyReturns204 flag has been set. If this flag is not set, (and you want to return NOCONTENT) then you need to use TServiceCustomAnswer.

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#7 2024-01-21 07:52:46

ab
Administrator
From: France
Registered: 2010-06-21
Posts: 14,706
Website

Re: Returning TServiceCustomStatus from interface method

rsoHttp200WithNoBodyReturns204 is at REST level, but there is a similar automatic feature - with no flag, at HTTP server level IIRC.

Edit: I was wrong, there is no automated HTTP_NOCONTENT setting at HTTP server level.
But if you use TServiceCustomStatus, it is likely to have a JSON result content generated by the REST routing class, so there will be a body output, and HTTP_NOCONTENT won't be correct.
So you can't use TServiceCustomStatus to generate void content, but need to use TServiceCustomAnswer.

I tried to refine the doc again
https://github.com/synopse/mORMot2/commit/332ff138

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