[SOLVED] [Brook] Address book question: handling 404
lazarus / 38-Networking and Web Programming

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BigChimp · 2013-02-19 09:41

Hi all (& Silvio  )

In the Brook REST addressbook client application there's code like
this:
Code: [Select]class function TfrCustomEdit.ProcessRequest(
  const AHttpResult: THttpResult): Boolean;
begin
  Result := (AHttpResult.Code = 200) or (AHttpResult.Code = 201) or
    (AHttpResult.Code = 204) or (AHttpResult.Code = 404);
  if not Result then
    ShowMessageFmt('ERROR: Text: %s; code: %d.',
      [AHttpResult.Text, AHttpResult.Code]);
end;
It seems like 404 errors are silently ignored. Doesn't that hide a bit
too much (note: REST/web programming newb here, I'm just assuming 404
means something like "resource not found")

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Silvio Clécio · 2013-02-19 22:52

Hello guy!

404 is handled by the broker, so it can be returned by the requester.

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Silvio Clécio · 2013-02-19 22:54

... the result for 404 is:

Code: [Select]{ "error": "Not found." }

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BigChimp · 2013-02-20 06:50

Thanks Silvio... I'm not clear about how the addressbook client goes
through Brook then but I'll figure it out

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BigChimp · 2013-02-21 09:22

Had another look and I'm fairly sure you are talking about the
*server* part, not the addressbook *client* part.

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Silvio Clécio · 2013-02-21 14:46

Hello,

I use two tools to debug my REST APIs:

. http://imagebin.org/247563 (HttpRequester - Firefox plugin)
. http://imagebin.org/247564 (Chrome debug - Type F12 in your Chrome)

I do not know what would I do without these tools.

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BigChimp · 2013-02-21 14:53

Nice

I still have the feeling you are talking about the server. I am
talking about the addressbook client demo program included with Brook.
It seems to ignore 404 responses by the server, as fa as I can tell by
the code.

What about changing this:
brookframework\demos\db\rest\addressbook\frontend\frmcustomedit.pas
Code: [Select]class function TfrCustomEdit.ProcessRequest(
  const AHttpResult: THttpResult): Boolean;
begin
  Result := (AHttpResult.Code = 200) or (AHttpResult.Code = 201) or
    (AHttpResult.Code = 204) or (AHttpResult.Code = 404);
  if not Result then
    ShowMessageFmt('ERROR: Text: %s; code: %d.',
      [AHttpResult.Text, AHttpResult.Code]);
end;

to this:
Code: [Select]class function TfrCustomEdit.ProcessRequest(
  const AHttpResult: THttpResult): Boolean;
begin
  Result := (AHttpResult.Code = 200) or (AHttpResult.Code = 201) or
    (AHttpResult.Code = 204); // <------------- NO MORE
404!!!!!!!!!!!!!!!!ELEVEN!!!!!!!!!!!!ONE!!!!!
  if not Result then
    ShowMessageFmt('ERROR: Text: %s; code: %d.',
      [AHttpResult.Text, AHttpResult.Code]);
end;

... so the end user gets to see the error if the server URLs don't
match anymore?

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Silvio Clécio · 2013-02-21 16:42

Ah, now I understood.

REST return 404 if the resource don't exists. 404 for REST isn't
error, but a status code. The addressbook demo implement it (like it
http://phprestsql.sourceforge.net). To test it is very easy, follow
steps below:

1. Comment your 404 code:

Code: [Select]class function TfrCustomEdit.ProcessRequest(
  const AHttpResult: TBrookHTTPResult): Boolean;
begin
  Result := (AHttpResult.StatusCode = 200) or (AHttpResult.StatusCode
= 201) or
    (AHttpResult.StatusCode = 204);// or (AHttpResult.StatusCode =
404);
  if not Result then
    ShowMessageFmt('ERROR: Text: %s; code: %d.',
      [AHttpResult.ReasonPhrase, AHttpResult.StatusCode]);
end;
2. Run the demo and add a new contact;
3. Now, select the new contact added;

In step 3 it will return a 404 error, but if you keep the "or
(AHttpResult.StatusCode = 404)" it work correctly.

So, the demo can be changed to (please test it via GIT copy):

Code: [Select]class function TfrCustomEdit.ProcessRequest(
  const AHttpResult: TBrookHTTPResult): Boolean;
begin
  Result := AHttpResult.StatusCode = 404;
  if Result then
  begin
    ShowMessage('No record(s).');
    Exit;
  end;
  Result := (AHttpResult.StatusCode = 200) or (AHttpResult.StatusCode
= 201) or
    (AHttpResult.StatusCode = 204);
  if not Result then
    ShowMessageFmt('ERROR: Text: %s; code: %d.',
[AHttpResult.ReasonPhrase,
      AHttpResult.StatusCode]);
end;

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BigChimp · 2013-02-22 05:09

Thanks a lot, Silvio, now I understand

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Silvio Clécio · 2013-02-22 11:14

Fine.