How can I accept gzip-compressed content using LWP

问题:

I am fetching some pages over the Web using Perl's LWP::UserAgent and would like to be as polite as possible. By default, LWP::UserAgent does not seamlessly handle compressed content via gzip. Is there an easy way to make it do so, to save everyone some bandwidth?

回答1:

LWP has this capability built in, thanks to HTTP::Message. But it's a bit hidden.

First make sure you have Compress::Zlib installed so you can handle gzip. HTTP::Message::decodable() will output a list of allowed encodings based on the modules you have installed; in scalar context, this output takes the form a comma-delineated string that you can use with the 'Accept-Encoding' HTTP header, which LWP requires you to add to your HTTP::Request-s yourself. (On my system, with Compress::Zlib installed, the list is "gzip, x-gzip, deflate".)

When your HTTP::Response comes back, be sure to access the content with $response->decoded_content instead of $response->content.

In LWP::UserAgent, it all comes together like this:

my $ua = LWP::UserAgent->new;
my $can_accept = HTTP::Message::decodable;
my $response = $ua->get('http://stackoverflow.com/feeds', 
    'Accept-Encoding' => $can_accept,
);
print $response->decoded_content;

This will also decode text to Perl's unicode strings. If you only want LWP to uncompress the response, and not mess with the text, do like so:

print $response->decoded_content(charset => 'none');