GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages
LWP::Protocol::PSGI(3) User Contributed Perl Documentation LWP::Protocol::PSGI(3)

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

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

  # can be Mojolicious, Catalyst, Dancer2 or any PSGI application
  my $psgi_app = do {
      use Dancer;
      set 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

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

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.

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 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.

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
2014-05-19 perl v5.32.1

Search for    or go to Top of page |  Section 3 |  Main Index

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with ManDoc.