OK, I retrieved the value of AvantGo HTTP headers, and it is all gobbledygook! What is wrong?
This is where it gets a little tricky. Most of the values of AvantGo headers are Base64-encoded before they are sent across. So you might find that your X-AvantGo-Screensize header has a value equal to something like MTUweDE1MA==. You will need to decode these headers before you can actually deal with them in a reasonable manner.
Decoding a Base64 Encoded string is generally pretty easy, albeit a little obscure. It is a little different depending on what you are using to serve up pages:
Please note that AvantGo cannot provide support for the various third-party libraries. You are better off contacting these third parties directly.
For example, here is a Perl script that prints a custom front page based on the user's mobile device. It analyzes the bit depth and chooses a logo based on that value. Then it analyzes the device's operating system and prints out some text based on that value.
#!D:\Perl\bin\perl.exe
use CGI qw/:standard/;
use MIME::Base64;
# devicecontext.pl
#
# Todd's sample code for changing images and text
# based on what AvantGo headers we receive
#
# Note that I am using Perl on a Apache Server on an
# NT machine, hence the weird first line.
# Just print out the beginning...
print "Content-type: text/html\n";
print "Cache-Control: max-age=7200\n";
print <<END_of_Start;
<HTML>
<HEAD>
<TITLE>Greetings</TITLE>
<META Name="HandheldFriendly" content="True">
</HEAD>
<BODY>
END_of_Start
# And now process the headers.
#
# We're only going to look for the AvantGo headers
# we're interested in (COLORDEPTH and DEVICEOS)
#
# They need to be base64-decoded before we can do
# anything useful to them so I'm using the decode_base64
# function that's included in Perl's MIME:Base64 library.
$colordepth = decode_base64(http('HTTP_X_AVANTGO_COLORDEPTH'));
$deviceos = decode_base64(http('HTTP_X_AVANTGO_DEVICEOS'));
print "<center><b>Greetings!</b><p>And welcome
to...<\p>\n";
if ($colordepth > 2) {
# If the colordepth is greater than 2, print the color logo
print "<img src=\"/colorlogo.gif\" alt=\"MyCompany.com\">\n ";,
} else {
# Otherwise, we'll go with the black and white logo
print "<img src=\"/bwlogo.gif\"
alt=\"MyCompany.com\">\n";
}
if ($deviceos eq 'PALM_OS') {
print "<p>The website that puts PalmOS users first!\n";
} elsif ($deviceos eq 'WINCE_OS') {
print "<p>The website that puts Pocket PC users
first!\n";
} else {
print "<p>The website that puts non-Palm and Pocket PC
users first!\n";
}
print "</center></body></HTML>\n";
#
# Copyright (c) 2000, AvantGo, Inc., all rights reserved.
#
# AVANTGO MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT
# THE SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
# PURPOSE, OR NON-INFRINGEMENT. AVANTGO SHALL NOT BE
# LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT
# OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR
# ITS DERIVATIVES.
Here is the same page in PHP.
<?php header("Cache-Control: max-age=7200");
?>
<HTML>
<HEAD>
<TITLE>Greetings</TITLE>
<META Name="HandheldFriendly" Content="TRUE">
</HEAD>
<BODY>
<center>
<b>Greetings!</b>
<p>And welcome to...</p>
<?php
$colordepth=base64_decode(getenv("HTTP_X_AVANTGO_COLORDEPTH"));
$deviceos = base64_decode(getenv("HTTP_X_AVANTGO_DEVICEOS"));
if ($colordepth > 2) {
print( "<img src=\"/colorlogo.gif\"
alt=\"MyCompany.com\">\n");
} else {
print( "<img src=\"\bwlogo.gif\"
alt=\"MyCompany.com\">\n");
}
if ($deviceos == 'PALM_OS') {
print ("<p>The website that puts PalmOS users
first!\n");
} elseif ($deviceos == 'WINCE_OS') {
print ("<p>The website that puts Pocket PC users
first!\n");
} else {
print ("<p>The website that puts Pocket PC and non-
Palm users first!\n");
}
?>
</center>
</body>
</html>
<?php
#
# Copyright (c) 2000, AvantGo, Inc., all rights reserved.
#
# AVANTGO MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT
# THE SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
# PURPOSE, OR NON-INFRINGEMENT. AVANTGO SHALL NOT BE
# LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT
# OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR
# ITS DERIVATIVES.
?>
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