HTTP saves time, saves money, saves you

It Italy, as usual, our govern is a mess when talking about {insert any topic here}: today's topic will be... webservices, saving money, time and providing an efficient service to the citizens.

Veryfing a VAT number

A requirement in your projects could be to verify, when a user subscribes to your service, which is intended for business owners, his VAT number.

The italian govern has such a service in the form of a webpage, thus thought for humans: they don't offer a specific webservice but that's not a problem, as I can submit the form ( it uses GET, which is exactly meant for the purpose ) with an HTTP request. Cool.

Doing HTTP wrong

So the first thing that came to my mind was to use cURL to verify the service:

curl -I -X GET http://www1.agenziaentrate.it/servizi/vies/transazione.htm -d "s=IT&p=02524130305" -G

where s is the country of the company and p its VAT number (bare in mind that the VAT number used here is wrong, as it was the one of my first company, now closed).

Bare in mind that:

GET /vats?s=IT&p=02524130305

logically equals to

GET /vats/IT/02524130305

The result?

HTTP/1.1 200 OK
Date: Wed, 21 Sep 2011 13:02:25 GMT
Server: Apache
X-Powered-By: PHP/4.3.11
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html

First of all, let's try not to be angry for that X-Powered-By header right there: let's just ignore it :-|

Then... Oh, wow, 200 OK.

Why is this so bad?

At first glance, it seemed weird to me, but I tought that they, for some reasons, considered my old company's VAT number still valid, but then I realized how much noob an entire IT department can be so I started suspecting that the system was responding 200 to every request.

Guess what, I was right.

I repeated the cURL call omitting the -I option (retrieve headers only) and saw the entire response body: in a table, beautiful as the sun, "VAT number not found".

So, if I need to verify the existence of a VAT number with the tools provided by my govern, I need to parse an entire HTML document, look for a DOM element ( table#feedback > td and stuff like that ), parse the resulting string and... oh, I'm already annoyed by describing the steps to do it!

Take a look at the pseudo-code for this implementation:

vat = request.get('vat')
vatVerifyService = new ItalianGovernVatService 

vatResponse = vatVerifyService.check(vat)

if (vatResponse) {
  body = varResponse.getBody()

  // parse the body
  // look for a DOM attribute,
  // which will change as they update the website with a new fancy markup
  // then evaluate the resulting string
} 

and your code if you keep HTTP in consideration:

vat = request.get('vat')
vatVerifyService = new ItalianGovernVatService 

vatResponse = vatVerifyService.check(vat)
// vatResponse.getCode() tells you if the VAT is good or not 

Ok, this resource is not intended to be a machine-consumed service but:

• using the proper HTTP status code would have saved my time
• using the proper HTTP status code helps you expose a resource that, in some cases like this one, can be useful to both human-beings and computer programs, without writing any line of code, thus without wasting money

Adapt your resources and domain application protocols to HTTP: this is the only way to save your and your consumers' money and time in the modern web.

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