NAME

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

SYNOPSIS

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

         # $app can be any PSGI application: Mojolicious, Catalyst or your own
         my $app = do {
             use Dancer;
             set apphandler => 'PSGI';
             get '/search' => sub {
                 return 'searching for ' . params->{q};
             };
             dance;
         };

         # Register the $app to handle all LWP requests
         LWP::Protocol::PSGI->register($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; # "searching for bar"

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

         my $ua = LWP::UserAgent->new;
         $ua->get("http://localhost:3000/app"); # this routes $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

TESTING

       This module is extremely handy if you have tests that run HTTP requests against your application and want
       them to work with both internal and external instances.

         # in your .t file
         use Test::More;
         use LWP::UserAgent;

         unless ($ENV{TEST_LIVE}) {
             require LWP::Protocol::PSGI;
             my $app = Plack::Util::load_psgi("app.psgi");
             LWP::Protocol::PSGI->register($app);
         }

         my $ua = LWP::UserAgent->new;
         my $res = $ua->get("http://myapp.example.com/");
         is $res->code, 200;
         like $res->content, qr/Hello/;

       This test script will by default route all HTTP requests to your own PSGI app defined in $app, but with
       the environment variable "TEST_LIVE" set, runs the requests against the live server.

       You can also combine Plack::App::Proxy with LWP::Protocol::PSGI to route all requests made in your test
       against a specific server.

         use LWP::Protocol::PSGI;
         use Plack::App::Proxy;

         my $app = Plack::App::Proxy->new(remote => "http://testapp.local:3000")->to_app;
         LWP::Protocol::PSGI->register($app);

         my $ua = LWP::UserAgent->new;
         my $res = $ua->request("http://testapp.com"); # this hits testapp.local:3000

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 one 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.

SEE ALSO

       Plack::Client LWP::UserAgent