XML::RSS::LibXML(3) User Contributed Perl Documentation XML::RSS::LibXML(3)NAMEXML::RSS::LibXML - XML::RSS with XML::LibXML
SYNOPSIS
use XML::RSS::LibXML;
my $rss = XML::RSS::LibXML->new;
$rss->parsefile($file);
print "channel: $rss->{channel}->{title}\n";
foreach my $item (@{ $rss->{items} }) {
print " item: $item->{title} ($item->{link})\n";
}
# Add custom modules
$rss->add_module(uri => $uri, prefix => $prefix);
# See docs for XML::RSS for these
$rss->channel(...);
$rss->add_item(...);
$rss->image(...);
$rss->textinput(...);
$rss->save(...);
$rss->as_string($format);
# XML::RSS::LibXML only methods
my $version = $rss->version;
my $base = $rss->base;
my $hash = $rss->namespaces;
my $list = $rss->items;
my $encoding = $rss->encoding;
my $modules = $rss->modules;
my $output = $rss->output;
my $stylesheets = $rss->stylesheets;
my $num_items = $rss->num_items;
DESCRIPTIONXML::RSS::LibXML uses XML::LibXML (libxml2) for parsing RSS instead of
XML::RSS' XML::Parser (expat), while trying to keep interface
compatibility with XML::RSS.
XML::RSS is an extremely handy tool, but it is unfortunately not
exactly the most lean or efficient RSS parser, especially in a long-
running process. So for a long time I had been using my own version of
RSS parser to get the maximum speed and efficiency - this is the re-
packaged version of that module, such that it adheres to the XML::RSS
interface.
Use this module when you have severe performance requirements working
with RSS files.
VERSION 0.30
The original XML::RSS has been evolving in fairly rapid manner lately,
and that meant that there were a lot of features to keep up with. To
keep compatibility, I've had to pretty much rewrite the module from
ground up.
Now XML::RSS::LibXML is *almost* compatible with XML::RSS. If there are
problems, please send in bug reports (or more preferrably, patches ;)
COMPATIBILITY
There seems to be a bit of confusion as to how compatible
XML::RSS::LibXML is with XML::RSS: XML::RSS::LibXML is NOT 100%
compatible with XML::RSS. For instance XML::RS::LibXML does not do a
complete parsing of the XML document because of the way we deal with
XPath and libxml's DOM (see CAVEATS below)
On top of that, I originally wrote XML::RSS::LibXML as sort of a fast
replacement for XML::RAI, which looked cool in terms of abstracting the
various modules. And therefore versions prior to 0.02 worked more like
XML::RAI rather than XML::RSS. That was a mistake in hind sight, so it
has been addressed (Since XML::RSS::LibXML version 0.08, it even
supports writing RSS :)
From now on XML::RSS::LibXML will try to match XML::RSS's functionality
as much as possible in terms of parsing RSS feeds. Please send in
patches and any tests that may be useful!
PARSED STRUCTURE
Once parsed the resulting data structure resembles that of XML::RSS.
However, as one addition/improvement, XML::RSS::LibXML uses a technique
to allow users to access complex data structures that XML::RSS doesn't
support as of this writing.
For example, suppose you have a tag like the following:
<rss version="2.0" xml:base="http://example.com/">
...
<channel>
<tag attr1="val1" attr2="val3">foo bar baz</tag>
</channel>
</rss>
All of the fields in this construct can be accessed like so:
$rss->channel->{tag} # "foo bar baz"
$rss->channel->{tag}{attr1} # "val1"
$rss->channel->{tag}{attr2} # "val2"
See XML::RSS::LibXML::MagicElement for details.
METHODS
new(%args)
Creates a new instance of XML::RSS::LibXML. You may specify a version
or an XML base in the constructor args to control which output format
as_string() will use.
XML::RSS::LibXML->new(version => '1.0', base => 'http://example.com/');
The XML base will be included only in RSS 2.0 output. You can also
specify the encoding that you expect this RSS object to use when
creating an RSS string
XML::RSS::LiBXML->new(encoding => 'euc-jp');
parse($string)
Parse a string containing RSS.
parsefile($filename)
Parse an RSS file specified by $filename
channel(%args)
add_item(%args)
image(%args)
textinput(%args)
These methods are used to generate RSS. See the documentation for
XML::RSS for details. Currently RSS version 0.9, 1.0, and 2.0 are
supported.
Additionally, add_item takes an extra parameter, "mode", which allows
you to add items either in front of the list or at the end of the list:
$rss->add_item(
mode => "append",
title => "...",
link => "...",
);
$rss->add_item(
mode => "insert",
title => "...",
link => "...",
);
By default, items are appended to the end of the list
as_string($format)
Return the string representation of the parsed RSS. If $format is true,
this flag is passed to the underlying XML::LibXML object's toString()
method.
By default, $format is true.
add_module(uri => $uri, prefix => $prefix)
Adds a new module. You should do this before parsing the RSS.
XML::RSS::LibXML understands a few modules by default:
rdf => "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
dc => "http://purl.org/dc/elements/1.1/",
syn => "http://purl.org/rss/1.0/modules/syndication/",
admin => "http://webns.net/mvcb/",
content => "http://purl.org/rss/1.0/modules/content/",
cc => "http://web.resource.org/cc/",
taxo => "http://purl.org/rss/1.0/modules/taxonomy/",
So you do not need to add these explicitly.
save($file)
Saves the RSS to a file
items()
Syntactic sugar to allow statement like this:
foreach my $item ($rss->items) {
...
}
Instead of
foreach my $item (@{$rss->{items}}) {
...
}
In scalar context, returns the reference to the list of items.
create_libxml()
Creates, configures, and returns an XML::LibXML object. Used by
"parse()" to instantiate the parser used to parse the feed.
PERFORMANCE
Here's a simple benchmark using benchmark.pl in this distribution,
using XML::RSS 1.29_02 and XML::RSS::LibXML 0.30
daisuke@beefcake XML-RSS-LibXML$ perl -Mblib tools/benchmark.pl t/data/rss20.xml
XML::RSS -> 1.29_02
XML::RSS::LibXML -> 0.30
Rate rss rss_libxml
rss 25.6/s -- -67%
rss_libxml 78.1/s 205% --
CAVEATS
- Only first level data under <channel> and <item> tags are examined.
So if you have complex data, this module will not pick it up. For most
of the cases, this will suffice, though.
- Namespace for namespaced attributes aren't properly parsed as part of
the structure. Hopefully your RSS doesn't do something like this:
<foo bar:baz="whee">
You won't be able to get at "bar" in this case:
$xml->{foo}{baz}; # "whee"
$xml->{foo}{bar}{baz}; # nope
- Some of the structures will need to be handled via
XML::RSS::LibXML::MagicElement. For example, XML::RSS's SYNOPSIS shows
a snippet like this:
$rss->add_item(title => "GTKeyboard 0.85",
# creates a guid field with permaLink=true
permaLink => "http://freshmeat.net/news/1999/06/21/930003829.html",
# alternately creates a guid field with permaLink=false
# guid => "gtkeyboard-0.85
enclosure => { url=> 'http://example.com/torrent', type=>"application/x-bittorrent" },
description => 'blah blah'
);
However, the enclosure element will need to be an object:
enclosure => XML::RSS::LibXML::MagicElement->new(
attributes => {
url => 'http://example.com/torrent',
type=>"application/x-bittorrent"
},
);
- Some elements such as permaLink elements are not really parsed such
that it can be serialized and parsed back and force. I could fix this,
but that would break some compatibility with XML::RSS
TODO
Tests. Currently tests are simply stolen from XML::RSS. It would be
nice to have tests that do more extensive testing for correctness
SEE ALSO
XML::RSS, XML::LibXML, XML::LibXML::XPathContext
COPYRIGHT AND LICENSE
Copyright (c) 2005-2007 Daisuke Maki <dmaki@cpan.org>, Tatsuhiko
Miyagawa <miyagawa@bulknews.net>. All rights reserved.
Many tests were shamelessly borrowed from XML::RSS 1.29_02
Development partially funded by Brazil, Ltd. <http://b.razil.jp>
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.1 2011-07-06 XML::RSS::LibXML(3)
