Problem importing URL with Greek characters

13

0

I'm considering buying a car. So I thought why not make a web-crawler in Mathematica to pile-up car data? Brilliant idea. Then I found this Greek website, gocar.gr, which just so happens to have all the data I need in a convenient form, with URLs following a very consistent progression:

www.gocar.gr/cars/BRAND/MODEL/EDITION

e.g. www.gocar.gr/cars/OPEL/MOKKA/1.7_CDTi_Edition_/.

The problem is when the model or edition contains Greek letters (but not the brand? Oh wait, there are no Greek car brands), e.g. www.gocar.gr/cars/BMW/ΣΕΙΡΑ_3/, in which case Import["URL", "Data"] fails with a FetchURL::conopen error.

It seems to me that this is some kind of encoding problem (it's consistent with Greek characters appearing in the URL and everything else works). I've seen the -kind of- relevant questions about copying non-Unicode text (this and this), but my problem is staying within Mathematica, not copying something out of it (which, by the way, works fine).

So, to reproduce:

Import["http://www.gocar.gr/cars/BMW","Data"]

works, but

Import["http://www.gocar.gr/cars/BMW/ΣΕΙΡΑ_3","Data"]

doesn't.

And my question is: any ideas?

Additional info:

  1. This is a Windows 7 / 64-bit computer; formats and location are set to Greek/Greece, Greek keyboard is installed (duh), display language is set to English, Mathematica version 8.

  2. I also tried going directly through the JLink with a Java module I found in some other post (can't find it right now; may credit go where credit is due):

    Needs["JLink`"]
    
    httpGet[url_String] :=JavaBlock @
    Module[{http, get}, 
           http = JavaNew["org.apache.commons.httpclient.HttpClient"];
           get = JavaNew["org.apache.commons.httpclient.methods.GetMethod", url];
           http @ executeMethod[get]; get @ getResponseBodyAsString[]]
    

    followed by:

    ImportString[httpGet[URL - HERE], {"HTML", "Data"}]
    

    No luck.

Thank you for reading my rant.

kalt

Posted 2013-06-12T17:46:01.287

Reputation: 343

1This is probably the post you were referring to... – rm -rf – 2013-06-12T17:48:16.967

Well, good question -- +1. But, I don't know what to tell you besides that this was apparently a bug in version 8, since it works correctly in version 9. – Oleksandr R. – 2013-06-12T18:06:19.073

I second that. Works for me Win7-64, MMA v9.01 – Sjoerd C. de Vries – 2013-06-12T18:14:20.457

2What if you percent-encode the URLs with Greek stuff? – J. M.'s ennui – 2013-06-12T18:29:26.507

@rm-rf yes, thank you. – kalt – 2013-06-12T18:39:35.317

@0x4A4D percent encoding does work – Oleksandr R. – 2013-06-12T18:40:40.957

2@0x4A4D well, "http%3A%2F%2Fwww.gocar.gr%2Fcars%2FBMW%2F%CE%A3%CE%95%CE%99%CE%A1%CE%91_3%2F" doesn't work (as expected; and it's ugly, too), but percent-encoding just e.g. "ΣΕΙΡΑ_3" in UTF8 (as in "%CE%A3%CE%95%CE%99%CE%A1%CE%91_3") does! Now that's mildly sub-optimal, but it does work. Thank you sir, you are a beautiful -unicode- character. (PS: I kind-of tried this by encoding the whole URL in ISO8859-1, which didn't work, and then I gave up. So, thank you for insisting.) – kalt – 2013-06-12T18:51:14.767

2@kalt percent encoding is only meant for the path elements of the URL (and/or parameters)--not the protocol, domain name, or path separators. That's why you need to encode only the Greek text: it's not a valid URL otherwise. – Oleksandr R. – 2013-06-12T18:55:04.320

@kalt You might be interested in this answer by Todd Gayley (esp. the encode). So if you're building an app, all this encoding can be done in the backend and the user will never know.

– rm -rf – 2013-06-12T19:31:05.583

Answers

6

The specification RFC1738 : "Uniform Resource Locators" states that:

The characters ";", "/", "?", ":", "@", "=" and "&" are the characters which may be reserved for special meaning within a scheme. No other characters may be reserved within a scheme.

[...] only alphanumerics, the special characters "$-_.+!*'(),", and reserved characters used for their reserved purposes may be used unencoded within a URL.

Since the list of reserved/special characters is small, we can write an automated solution (instead of having to manually identify the Greek parts and encode like in kalt's answer) using ExternalService`EncodeString from here as:

encodeURL[str_String] := StringReplace[str, 
    x : Except[Alternatives @@ Characters@";/?:@=&$-_.+!*'()"] :> 
        ExternalService`EncodeString[x]]

(alphanumerics are handled correctly by EncodeString). We can now directly encode the URL:

encodeURL["http://www.gocar.gr/cars/BMW/ΣΕΙΡΑ_3"]
(* "http://www.gocar.gr/cars/BMW/%CE%A3%CE%95%CE%99%CE%A1%CE%91_3" *)

rm -rf

Posted 2013-06-12T17:46:01.287

Reputation: 85 395

1+1, but this is not correct for Unicode-based domain names. Those should be encoded using Punycode, not percent-encoding. – Oleksandr R. – 2013-06-13T10:21:01.970

9

Just in case somebody else needs it, here is a compiled answer. Thanks go out to 0x4A4D (for the actual solution), Michael Pilat (for the JLink part) and everybody else in here for the swift responses.

Since this is apparently a bug of sorts in Mathematica 8, percent encoding the Greek letters in the URL will have to do.

Reciting Michael Pilat's code snippet:

Needs["JLink`"]; 
InstallJava[];
LoadJavaClass["java.net.URLEncoder"];

percentEncode[allGreekToMe_]:=URLEncoder`encode[allGreekToMe,"UTF-8"]

where 'allGreekToMe' is the Greek string. So, the following will now work:

Import["http://www.gocar.gr/cars/BMW/"<>percentEncode["ΣΕΙΡΑ_3","UTF-8"],"Data"]

And no, I'm not buying a BMW.

kalt

Posted 2013-06-12T17:46:01.287

Reputation: 343