Programming Jabber

The RSS mechanism

Now that we’ve set up the functions to handle incoming queries, all that’s left is for us to define what happens every time the heartbeat in the Jabber::Connection loop ticks past the 30-minute mark. We registered this rss() function with the register_beat() method earlier in the script:

sub rss {

  debug("[rss]");

  # Create NodeFactory
  my $nf = new Jabber::NodeFactory;

In the IQ handlers iq-register(), iq-version(), iq-browse(), and iq-notimpl(), we avoided the need to build elements from scratch, by simply turning around the incoming request elements and making them into responses, before sending them back. Here, in the rss() function, we’ll actually be building elements from scratch—headline type <message> elements to be precise. This is the reason we need an instance of the Jabber::NodeFactory.

  # Go through each of the RSS sources
  foreach my $source (keys %sources) {

    # Retrieve attempt
    my $data = get($sources{$source});

    # Didn't get it? Next one
    unless (defined($data)) {
      debug("cannot retrieve $source");
      next;
    }

    # Parse the RSS
    my $rss = XML::RSS->new();
    eval { $rss->parse($data) };

    if ($@) {
      debug("Problems parsing $source");
      next;
    }

The procedure in this function reflects what we described earlier in Section 9.3.1.3. Each time rss() is called, it goes through each of the sources defined in the list (%sources) and tries to retrieve it with get(), a function from the LWP::Simple library, and parse it with an instance of XML::RSS. Because XML::RSS uses XML::Parser ...