Ubuntu Manpage: LWP::Protocol::PSGI - Override LWP's HTTP/HTTPS backend with your own PSGI applciation

Provided by: liblwp-protocol-psgi-perl_0.06-2_all

NAME

       LWP::Protocol::PSGI - Override LWP's HTTP/HTTPS backend with your own PSGI applciation

SYNOPSIS

         use LWP::UserAgent;
         use LWP::Protocol::PSGI;

         # can be Mojolicious, Catalyst ... any PSGI application
         my $psgi_app = do {
             use Dancer;
             setting apphandler => 'PSGI';
             get '/search' => sub {
                 return 'googling ' . params->{q};
             };
             dance;
         };

         # Register the $psgi_app to handle all LWP requests
         LWP::Protocol::PSGI->register($psgi_app);

         # can hijack any code or module that uses LWP::UserAgent underneath, with no changes
         my $ua  = LWP::UserAgent->new;
         my $res = $ua->get("http://www.google.com/search?q=bar");
         print $res->content; # "googling bar"

         # Only hijacks specific hosts
         LWP::Protocol::PSGI->register($psgi_app, host => 'localhost:3000');

         my $ua = LWP::UserAgent->new;
         $ua->get("http://localhost:3000/app"); # this routes $psgi_app
         $ua->get("http://google.com/api");     # this doesn't - handled with actual HTTP requests

DESCRIPTION

       LWP::Protocol::PSGI is a module to hijack any code that uses LWP::UserAgent underneath such that any HTTP
       or HTTPS requests can be routed to your own PSGI application.

       Because it works with any code that uses LWP, you can override various WWW::*, Net::* or WebService::*
       modules such as WWW::Mechanize, without modifying the calling code or its internals.

         use WWW::Mechanize;
         use LWP::Protocol::PSGI;

         LWP::Protocol::PSGI->register($my_psgi_app);

         my $mech = WWW::Mechanize->new;
         $mech->get("http://amazon.com/"); # $my_psgi_app runs

METHODS

       register
             LWP::Protocol::PSGI->register($app, %options);
             my $guard = LWP::Protocol::PSGI->register($app, %options);

           Registers  an override hook to hijack HTTP requests. If called in a non-void context, returns a Guard
           object that automatically resets the override when it goes out of context.

             {
                 my $guard = LWP::Protocol::PSGI->register($app);
                 # hijack the code using LWP with $app
             }

             # now LWP uses the original HTTP implementations

           When %options is specified, the option limits which URL and hosts this  handler  overrides.  You  can
           either pass "host" or "uri" to match requests, and if it doesn't match, the handler falls back to the
           original LWP HTTP protocol implementor.

             LWP::Protocol::PSGI->register($app, host => 'www.google.com');
             LWP::Protocol::PSGI->register($app, host => qr/\.google\.com$/);
             LWP::Protocol::PSGI->register($app, uri => sub { my $uri = shift; ... });

           The  options  can  take  either  a  string, where it does a complete match, a regular expression or a
           subroutine reference that returns boolean given the value of "host" (only the hostname) or "uri" (the
           whole URI, including query parameters).

       unregister
             LWP::Protocol::PSGI->unregister;

           Resets all the overrides for LWP. If you  use  the  guard  interface  described  above,  it  will  be
           automatically called for you.

DIFFERENCES WITH OTHER MODULES

Mock vs Protocol handlers
There are similar modules on CPAN that allows you to emulate LWP requests and responses. Most of them are
implemented as a mock library, which means it doesn't go through the LWP guts and just gives you a
wrapper for receiving HTTP::Request and returning HTTP::Response back.

LWP::Protocol::PSGI is implemented as an LWP protocol handler and it allows you to use most of the LWP
extensions to add capabilities such as manipulating headers and parsing cookies.

Test::LWP::UserAgent
Test::LWP::UserAgent has the similar concept of overriding LWP request method with particular PSGI
applications. It has more features and options such as passing through the requests to the native LWP
handler, while LWP::Protocol::PSGI only allows to map certain hosts and ports.

Test::LWP::UserAgent requires you to change the instantiation of UserAgent from "LWP::UserAgent->new" to
"Test::LWP::UserAgent->new" somehow and it's your responsibility to do so. This mechanism gives you more
control which requests should go through the PSGI app, and it might not be difficult if the creation is
done in one place in your code base. However it might be hard or even impossible when you are dealing
with third party modules that calls LWP::UserAgent inside.

LWP::Protocol::PSGI affects the LWP calling code more globally, while having an option to enable it only
in a specific block, thus there's no need to change the UserAgent object manually, whether it is in your
code or CPAN modules.

AUTHOR

       Tatsuhiko Miyagawa <miyagawa@bulknews.net>

COPYRIGHT

       Copyright 2011- Tatsuhiko Miyagawa

LICENSE

       This  library  is  free  software;  you can redistribute it and/or modify it under the same terms as Perl
       itself.