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 aginst 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 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 <[email protected]>

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

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