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 <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

