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<html><head><title>A Comics Index (Perl and XML)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Erik T. Ray and Jason McIntosh" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="059600205XL" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl and XML" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl & XML" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch10_03.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="index/index.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr></table></div><h2 class="sect1">10.4. A Comics Index</h2><p>XSLT is one thing, but the potential for Perl, XML, and the Webworking together is as unlimited as, well, anything else you mightchoose to do with Perl and the Web. Sometimes youcan't just toss refactored XML at your clients, butmust write Perl that wrings interesting information out of XMLdocuments and builds something Webbish out of the results. We did alittle of that in the previous example, mixing the raw XSLT usagewhen transforming the DocBook documents with index page generation.</p><p>Since we've gone through all the trouble of coveringsyndication-enabling XML technologies such as RSS and ComicsML inthis chapter and <a href="ch09_01.htm">Chapter 9, "RSS, SOAP, and Other XML Applications "</a>, let'swrite a little program that uses web syndication. To prove (orperhaps belabor) a point, we'll construct a simpleCGI program that builds an index of the user'sfavorite online comics (which, in our fantasy world, all haveComicsML documents associated with them):</p><blockquote><pre class="code">#!/usr/bin/perl# A very simple ComicsML muncher; given a list of URLs pointing to# ComicsML documents, fetch them, flatten their strips into one list,# and then build a web page listing, linking to, and possibly# displaying these strips, sorted with newest first.use warnings;use strict;use XML::ComicsML; # ...so that we can build ComicsML objectsuse CGI qw(:standard);use LWP;use Date::Manip; # Cuz we're too bloody lazy to do our own date math# Let's assume that the URLs of my favorite Internet funnies' ComicsML# documents live in a plaintext file on disk, with one URL per line# (What, no XML? For shame...)my $url_file = $ARGV[0] or die "Usage: $0 url-file\n";my @urls; # List of ComicsML URLsopen (URLS, $url_file) or die "Can't read $url_file: $!\n";while (<URLS>) { chomp; push @urls, $_; }close (URLS) or die "Can't close $url_file: $!\n";# Make an LWP user agentmy $ua = LWP::UserAgent->new;my $parser = XML::ComicsML->new;my @strips; # This will hold objects representing comic stripsforeach my $url (@urls) { my $request = HTTP::Request->new(GET=>$url); my $result = $ua->request($request); my $comic; # Will hold the comic we'll get back if ($result->is_success) { # Let's see if the ComicsML parser likes it. unless ($comic = $parser->parse_string($result->content)) { # Doh, this is not a good XML document. warn "The document at $url is not good XML!\n"; next; } } else { warn "Error at $url: " . $result->status_line . "\n"; next; } # Now peel all the strips out of the comic, pop each into a little # hashref along with some information about the comic itself. foreach my $strip ($comic->strips) { push (@strips, {strip=>$strip, comic_title=>$comic->title, comic_url=>$comic->url}); }}# Sort the list of strips by date. (We use Date::Manip's exported# UnixDate function here, to turn their unweildy Gregorian calendar# dates into nice clean Unixy ones)my @sorted = sort {UnixDate($$a{strip}->date, "%s") <=> UnixDate($$b{strip}->date, "%s")} @strips;# Now we build a web page!print header;print start_html("Latest comix");print h1("Links to new comics...");# Go through the sorted list in reverse, to get the newest at the top.foreach my $strip_info (reverse(@sorted)) { my ($title, $url, $svg); my $strip = $$strip_info{strip}; $title = join (" - ", $strip->title, $strip->date); # Hyperlink the title to a URL, if there is one provided if ($url = $strip->url) { $title = "<a href='$url'>$title</a>"; } # Give similar treatment to the comics' title and URL my $comic_title = $$strip_info{comic_title}; if ($$strip_info{comic_url}) { $comic_title = "<a href='$$strip_info{comic_url}'>$comic_title</a>"; } # Print the titles print p("<b>$comic_title</b>: $title"); print "<hr />";}print end_html;</pre></blockquote><p>Given the trouble we went through with that<tt class="literal">Apache::DocBook</tt> trifle a little earlier, thisprogram might seem a tad too simple; it performs no caching, itcontains no governors for how many strips it will process, and itssense of web page layout isn't much to write homeabout. For a quick hack, though, it works great and demonstrates thebenefit of using helper modules like<tt class="literal">XML::ComicsML</tt>.</p><p>Our whirlwind tour of the world of Perl and XML ends here. As we saidat the start of this book, the relationship between these twotechnologies is still young, and it only just started to reach forits full potential while we were writing this book, as new parserslike <tt class="literal">XML::LibXML</tt> and philosophies like PerlSAX2emerged onto the scene during that time. We hope that we have givenyou enough information and encouragement to become part of thisscene, as it will continue to unfold in increasingly interestingdirections in the coming years.</p><p><tt class="literal"><aloha>Happy hacking!</aloha></tt></p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch10_03.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img alt="Home" border="0" src="../gifs/txthome.gif" /></a></td><td align="right" valign="top" width="228"><a href="index/index.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr><tr><td align="left" valign="top" width="228">10.3. Converting XML to HTML with XSLT </td><td align="center" valign="top" width="228"><a href="index/index.htm"><img alt="Book Index" border="0" src="../gifs/index.gif" /></a></td><td align="right" valign="top" width="228">Index</td></tr></table></div><hr width="684" align="left" /><img alt="Library Navigation Links" border="0" src="../gifs/navbar.gif" usemap="#library-map" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. 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