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Author image Tatsuhiko Miyagawa


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


  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};

  # Register the $psgi_app to handle all LWP requests

  # 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


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;


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


  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 eithe 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).


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


Tatsuhiko Miyagawa <miyagawa@bulknews.net>


Copyright 2011- Tatsuhiko Miyagawa


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


Plack::Client LWP::UserAgent