Leyland - RESTful web application framework based on Plack


        # in app.psgi:

        #!/usr/bin/perl -w

        use strict;
        use warnings;
        use MyApp;

        my $app = MyApp->new->to_app;


Leyland is a Plack-based application framework for building truely RESTful, MVC-style web applications. It is feature rich and highly extensible.


        Leyland v1.0.0 brings small changes that break backwords compatibility.
        Read the L<upgrading manual|Leyland::Manual::Upgrading> for more information.


  • Build truely RESTful web applications: Leyland was designed from the ground up according to the Representational State Transfer style of software architecture. Leyland applications perform real HTTP negotiations, (can) provide different representations of the same resource easily, respond with proper HTTP status codes, throw real HTTP exceptions, etc.

  • Automatic data (de)serialization - Leyland automatically serializes resources to representations in the format your client wants to receive, like JSON and XML. It will also automatically deserialize JSON/XML requests coming from the client to Perl data-structures.

  • Pure UTF-8 - Leyland applications are pure UTF-8. Anything your application receives is automatically UTF-8 decoded, and anything your application sends is automatically UTF-8 encoded. Leyland apps will not accept, nor provide, content in a different character set. If you want to use different/multiple encodings, then Leyland is not for you.

  • Localize for the client, not the server - Pretty much every other application framework only concerns itself with localizing the application to the locale of the machine on which it is running. I find that this is rarely useful nor interesting to the application developer. Leyland localizes for the client, not the server. If the client wants to view your application (which may be a simple website) in Hebrew, and your application supports Hebrew, then you can easily provide him with Hebrew representations. Leyland uses Locale::Wolowitz for this purpose.

  • Easy deployment and middleware support via Plack - Leyland doesn't support Plack, it is dependant on it. Leyland's entire session support, for example, depends on Plack's Session middleware. Use the full power of Plack in your Leyland application.

  • Lightweight - Leyland is much smaller than Catalyst or other major frameworks, while still providing lots of features. While it is not a "micro-framework", it is pretty small. If you're looking for an extremely lightweight solution, my other framework - McBain - might fit your need.

  • Flexible, extensible - Leyland was designed to be as flexible and as extensible as possible - where flexibility matters, and strict - where constistency and convention are appropriate. Leyland goes to great lengths to give you the ability to do things the way you want to, and more importantly - the way your end-users want to. Your applications listen to your users' preferences and automatically decide on a suitable course of action. Leyland is also Moo based, making it easy to extend and tweak its behavior (and making it Moose compatible).

  • Doesn't have a pony - You don't really need a pony, do you?


To learn about using Leyland, please refer to the Leyland::Manual. The documentation of this distribution's classes is for reference only, the manual is where you're most likely to find your answers. Or not.


Major changes have been made in Leyland version 1.0.0. While most should be backwords compatible, some are not. Please take a look at the upgrading manual for a complete list of changes and a simple guide for upgrading existing applications.


Leyland is named after Mr. Bean's clunker of a car - the British Leyland Mini 1000. I don't know why.





The package name of the application, for example MyApp or My::App. Automatically created.


A hash-ref of configuration options supplied to the app by the PSGI file. These options are purely for the writer of the application and have nothing to do with Leyland itself.


The name of the class to be used as the context class for every request. Defaults to Leyland::Context. If provided, the class must extend Leyland::Context.


If application config defines a path for localization files, this will hold a Leyland::Localizer object, which is based on Locale::Wolowitz.


An array refernce of all Leyland::View classes enabled in the app's configuration. If none defined, Tenjin is used by default.


A Tie::IxHash object holding all routes defined in the application's controllers. Automatically created, not to be used directly by applications.


The plack environment in which the application is running. This is the PLACK_ENV environment variable. Defaults to "development" unless you've provided a specific value to plackup (via the -E switch or by changing PLACK_ENV directly).


new( [ %attrs ] )

Creates a new instance of this class. None of the attributes are required (in fact, you shouldn't pass most of them), though you can pass the config and context_class attributes if you need.



This method is not available by default, but is expected to be provided by application classes (though it is not required). If present, it will be called upon creation of the application object. The method is expected to return a hash-ref of Leyland-specific options. The following options are supported:

  • views

    A list of view classes to load. Defaults to ["Tenjin"].

  • view_dir

    The path to the directory in which views/templates reside (defaults to views).

  • locales

    The path to the directory in which localization files (in Locale::Wolowitz's format) reside (if localization is used).

  • default_mime

    The default return MIME type for routes that lack a specific declaration (defaults to text/html).

call( \%env )

The request handler. Receives a standard PSGI env hash-ref, creates a new instance of the application's context class (most probably Leyland::Context), performs HTTP negotiations and finds routes matching the request. If any are found, the first one is invoked and an HTTP response is generated and returned.

You should note that requests to paths that end with a slash will automatically be redirected without the trailing slash.


Returns a true value if the application has a localizer.


Returns a true value if the application has any view classes.


Returns a true value if the application has any routes defined in its controllers.


The following methods are only to be used internally.


Automatically called by Moo after instance creation, this method runs the applicaiton's setup() method (if any), loads the context class, localizer, controllers and views. It then find all routes in the controllers and prints a nice info table to the log.


Ido Perlmuter, <ido at>


I wish to thank the following people:


Please report any bugs or feature requests to bug-Leyland at, or through the web interface at I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


You can find documentation for this module with the perldoc command.

        perldoc Leyland

You can also look for information at:


Copyright 2010-2014 Ido Perlmuter.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See for more information.