Hack 92 Encode Text for URLs
 
Make sure the text in XML/HTTP queries is valid
for URLs.
One thing to keep in mind when making XML/HTTP
requests is that they behave exactly like URLs for web pages. This
means that spaces and symbols need to be
encoded. Spaces aren't allowed in URLs, so
anything after a space could be disregarded by the server. Also,
characters like ampersands (&), question marks
(?), and number signs (#) give
directions to the server about how the URL should be processed. So if
you're doing an XML/HTTP Amazon ArtistSearch for a
band like Kruder & Dorfmeister, you've got
trouble—the spaces and ampersand will break the request. But
you can translate the characters into a URL-friendly format.
Technically, you can encode these characters by using the percent
sign (%) followed by their hexadecimal numeric
values. The numeric value for a space is 20, so a
space is represented as %20 in a URL. Spaces can
also be escaped as plus signs (+) for many
systems, including Amazon's. Here are some commonly escaped
characters and their encoded values:
|
Ampersand (&)
|
%26
| |
Question mark (?)
|
%3F
| |
Number sign (#)
|
%23
| |
Comma (,)
|
%2C
| |
Colon (:)
|
%3A
|
The ArtistSearch mentioned will only work if the
band name is encoded as
Kruder%20%26%20Dorfmeister. Doing this by hand
each time you make a request is out of the question. Luckily, this is
such a common task that most programming environments have built-in
functions to handle this for you.
92.1 The Code
Here are few common ways to escape text for URLs in various scripting
languages.
- JavaScript
-
var artist = "Kruder & Dorfmeister";
artist = escape(artist);
- Perl
-
use URI::Escape;
my $artist = "Kruder & Dorfmeister";
$artist = uri_escape($artist);
- VBScript
-
strArtist = "Kruder & Dorfmeister"
strArtist = Server.URLEncode(strArtist)
- PHP
-
$artist = "Kruder & Dorfmeister";
$artist = urlencode(strArtist);
- Python
-
Unlike the previous examples, Python's
urlencode takes variable/value pairs and creates a
properly escaped querystring:
import sys
from urllib import urlencode
artist = "Kruder & Dorfmeister"
artist = urlencode({'ArtistSearch':artist})
This sets the variable artist equal to:
ArtistSearch=Kruder+%26+Dorfmeister
Encoding strings for URLs is an easy problem to solve, and it's
something to look at if your XML/HTTP requests aren't working
quite right.
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