NAME

Mojolicious::Guides::Routing - Routing

OVERVIEW

This document contains a simple and fun introduction to the Mojolicious router and its underlying concepts.

CONCEPTS

Essentials every Mojolicious developer should know.

Dispatcher

The foundation of every web framework is a tiny black box connecting incoming requests with code generating the appropriate response.

GET /user/show/1 -> $self->render(text => 'Sebastian');

This black box is usually called a dispatcher. There are many implementations using different strategies to establish these connections, but pretty much all are based around mapping the requests path to some kind of response generator.

/user/show/1 -> $self->render(text => 'Sebastian');
/user/show/2 -> $self->render(text => 'Sara');
/user/show/3 -> $self->render(text => 'Baerbel');
/user/show/4 -> $self->render(text => 'Wolfgang');

While it is very well possible to make all these connections static, it is also rather inefficient. That's why regular expressions are commonly used to make the dispatch process more dynamic.

qr|/user/show/(\d+)| -> $self->render(text => $users{$1});

Modern dispatchers have pretty much everything HTTP has to offer at their disposal and can use many more variables than just the request path, such as request method and headers like Host, User-Agent and Accept.

GET /user/show/23 HTTP/1.1
Host: mojolicio.us
User-Agent: Mozilla/5.0 (compatible; Mojolicious; Perl)
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Routes

While regular expressions are quite powerful they also tend to be unpleasant to look at and are generally overkill for ordinary path matching.

qr|/user/show/(\d+)| -> $self->render(text => $users{$1});

This is where routes come into play, they have been designed from the ground up to represent paths with placeholders.

/user/show/:id -> $self->render(text => $users{$id});

The only difference between a static path and the route above is the :id placeholder. One or more placeholders can be anywhere in the route.

/user/:action/:id

A fundamental concept of the Mojolicious router is that extracted placeholder values are turned into a hash.

/user/show/23 -> /user/:action/:id -> {action => 'show', id => 23}

This hash is basically the center of every Mojolicious application, you will learn more about this later on. Internally routes get compiled to regular expressions, so you can get the best of both worlds with a little bit of experience.

/user/show/:id -> qr/(?-xism:^\/user\/show/([^\/\.]+))/

A trailing slash is always optional.

/user/show/23/ -> /user/:action/:id -> {action => 'show', id => 23}

Reversibility

One more huge advantage routes have over regular expressions is that they are easily reversible, extracted placeholders can be turned back into a path at any time.

/sebastian -> /:name -> {name => 'sebastian'}
{name => 'sebastian'} -> /:name -> /sebastian

Generic placeholders

Generic placeholders are the simplest form of placeholders and match all characters except / and ..

/hello              -> /:name/hello -> undef
/sebastian/23/hello -> /:name/hello -> undef
/sebastian.23/hello -> /:name/hello -> undef
/sebastian/hello    -> /:name/hello -> {name => 'sebastian'}
/sebastian23/hello  -> /:name/hello -> {name => 'sebastian23'}
/sebastian 23/hello -> /:name/hello -> {name => 'sebastian 23'}

A generic placeholder can be surrounded by parentheses to separate it from the surrounding text.

/hello             -> /(:name)hello -> undef
/sebastian/23hello -> /(:name)hello -> undef
/sebastian.23hello -> /(:name)hello -> undef
/sebastianhello    -> /(:name)hello -> {name => 'sebastian'}
/sebastian23hello  -> /(:name)hello -> {name => 'sebastian23'}
/sebastian 23hello -> /(:name)hello -> {name => 'sebastian 23'}

Wildcard placeholders

Wildcard placeholders are just like generic placeholders, but match absolutely everything.

/hello              -> /*name/hello -> undef
/sebastian/23/hello -> /*name/hello -> {name => 'sebastian/23'}
/sebastian.23/hello -> /*name/hello -> {name => 'sebastian.23'}
/sebastian/hello    -> /*name/hello -> {name => 'sebastian'}
/sebastian23/hello  -> /*name/hello -> {name => 'sebastian23'}
/sebastian 23/hello -> /*name/hello -> {name => 'sebastian 23'}

Relaxed placeholders

Relaxed placeholders are similar to the two placeholders above, but always require parentheses and match all characters except /.

/hello              -> /(.name)/hello -> undef
/sebastian/23/hello -> /(.name)/hello -> undef
/sebastian.23/hello -> /(.name)/hello -> {name => 'sebastian.23'}
/sebastian/hello    -> /(.name)/hello -> {name => 'sebastian'}
/sebastian23/hello  -> /(.name)/hello -> {name => 'sebastian23'}
/sebastian 23/hello -> /(.name)/hello -> {name => 'sebastian 23'}

BASICS

Most commonly used features every Mojolicious developer should know about.

Minimal route

Every Mojolicious application has a router object you can use to generate routes structures.

# Application
package MyApp;
use Mojo::Base 'Mojolicious';

sub startup {
  my $self = shift;

  # Router
  my $r = $self->routes;

  # Route
  $r->route('/welcome')->to(controller => 'foo', action => 'welcome');
}

1;

The minimal static route above will load and instantiate the class MyApp::Foo and call its welcome method.

# Controller
package MyApp::Foo;
use Mojo::Base 'Mojolicious::Controller';

# Action
sub welcome {
  my $self = shift;

  # Render response
  $self->render(text => 'Hello there.');
}

1;

Routes are usually configured in the startup method of the application class, but the router can be accessed from everywhere (even at runtime).

Routing destination

After you start a new route with the route method you can also give it a destination in the form of a hash using the chained to method.

# /welcome -> {controller => 'foo', action => 'welcome'}
$r->route('/welcome')->to(controller => 'foo', action => 'welcome');

Now if the route matches an incoming request it will use the content of this hash to try and find appropriate code to generate a response.

Stash

The generated hash of a matching route is actually the center of the whole Mojolicious request cycle. We call it the stash, and it persists until a response has been generated.

# /bye -> {controller => 'foo', action => 'bye', mymessage => 'Bye'}
$r->route('/bye')
  ->to(controller => 'foo', action => 'bye', mymessage => 'Bye');

There are a few stash values with special meaning, such as controller and action, but you can generally fill it with whatever data you need to generate a response. Once dispatched the whole stash content can be changed at any time.

sub bye {
  my $self = shift;

  # Get message from stash
  my $message = $self->stash('mymessage');

  # Change message in stash
  $self->stash(mymessage => 'Welcome');
}

A full list of all reserved stash values can also be found in Mojolicious::Guides::Cheatsheet.

Special stash values (`controller` and `action`)

When the dispatcher sees controller and action values in the stash it will always try to turn them into a class and method to dispatch to. The controller value gets camelized and prefixed with a namespace (defaulting to the applications class) while the action value is not changed at all, because of this both values are case sensitive.

# Application
package MyApp;
use Mojo::Base 'Mojolicious';

sub startup {
  my $self = shift;

  # Router
  my $r = $self->routes;

  # /bye -> {controller => 'foo', action => 'bye'} -> MyApp::Foo->bye
  $r->route('/bye')->to(controller => 'foo', action => 'bye');
}

1;

# Controller
package MyApp::Foo;
use Mojo::Base 'Mojolicious::Controller';

# Action
sub bye {
  my $self = shift;

  # Render response
  $self->render(text => 'Good bye.');
}

1;

Controller classes are perfect for organizing code in larger projects. There are more dispatch strategies, but because controllers are the most commonly used ones they also got a special shortcut in the form of controller#action.

# /bye -> {controller => 'foo', action => 'bye', mymessage => 'Bye'}
$r->route('/bye')->to('foo#bye', mymessage => 'Bye');

During camelization - gets replaced with ::, this allows multi level controller hierarchies.

# / -> {controller => 'foo-bar', action => 'hi'} -> MyApp::Foo::Bar->hi
$r->route('/')->to('foo-bar#hi');

Route to class (`namespace`)

From time to time you might want to dispatch to a whole different namespace.

# /bye -> MyApp::Controller::Foo->bye
$r->route('/bye')
  ->to(namespace => 'MyApp::Controller::Foo', action => 'bye');

The controller is always appended to the namespace if available.

# /bye -> MyApp::Controller::Foo->bye
$r->route('/bye')->to('foo#bye', namespace => 'MyApp::Controller');

You can also change the default namespace for all routes in the application.

$r->namespace('MyApp::Controller');

Route to callback (`cb`)

You can use the cb stash value to bypass controllers and execute a callback instead.

$r->route('/bye')->to(cb => sub {
  my $self = shift;
  $self->render(text => 'Good bye.');
});

This technique is the foundation of Mojolicious::Lite, you can learn more about it from the included tutorial.

More restrictive placeholders

A very easy way to make placeholders more restrictive are alternatives, you just make a list of possible values.

# /bender -> {controller => 'foo', action => 'bar', name => 'bender'}
# /leela  -> {controller => 'foo', action => 'bar', name => 'leela'}
# /fry    -> undef
$r->route('/:name', name => ['bender', 'leela'])
  ->to(controller => 'foo', action => 'bar');

You can also adjust the regular expressions behind placeholders to better suit your needs. Just make sure not to use ^ and $ or capturing groups (...), because placeholders become part of a larger regular expression internally, (?:...) is fine though.

# /23   -> {controller => 'foo', action => 'bar', number => 23}
# /test -> undef
$r->route('/:number', number => qr/\d+/)
  ->to(controller => 'foo', action => 'bar');

# /23   -> undef
# /test -> {controller => 'foo', action => 'bar', name => 'test'}
$r->route('/:name', name => qr/[a-zA-Z]+/)
  ->to(controller => 'foo', action => 'bar');

This way you get easily readable routes and the raw power of regular expressions.

Formats

File extensions like .html and .txt at the end of a route are automatically detected and stored in the stash value format.

# /foo      -> {controller => 'foo', action => 'bar'}
# /foo.html -> {controller => 'foo', action => 'bar', format => 'html'}
# /foo.txt  -> {controller => 'foo', action => 'bar', format => 'txt'}
$r->route('/foo')->to(controller => 'foo', action => 'bar');

This for example allows multiple templates for different formats to share the same code. You can also mention a format in the route pattern to only match one, just make sure the more specific routes go first.

# /foo.txt -> {controller => 'foo', action => 'text', format => 'txt'}
$r->route('/foo.txt')->to(controller => 'foo', action => 'text');

# /foo      -> {controller => 'foo', action => 'hyper'}
# /foo.html -> {controller => 'foo', action => 'hyper', format => 'html'}
$r->route('/foo')->to(controller => 'foo', action => 'hyper');

Restrictive placeholders can also be used for format detection.

# /foo.rss -> {controller => 'foo', action => 'feed', format => 'rss'}
# /foo.xml -> {controller => 'foo', action => 'feed', format => 'xml'}
# /foo.txt -> undef
$r->route('/foo', format => ['rss', 'xml'])
  ->to(controller => 'foo', action => 'feed');

Or you can just disable format detection.

# /foo      -> {controller => 'foo', action => 'bar'}
# /foo.html -> undef
$r->route('/foo', format => 0)->to(controller => 'foo', action => 'bar');

Placeholders and destinations

Extracted placeholder values will simply redefine older stash values if they already exist.

# /bye -> {controller => 'foo', action => 'bar', mymessage => 'bye'}
# /hey -> {controller => 'foo', action => 'bar', mymessage => 'hey'}
$r->route('/:mymessage')
  ->to(controller => 'foo', action => 'bar', mymessage => 'hi');

One more interesting effect, if a placeholder is at the end of a route and there is already a stash value of the same name present, it automatically becomes optional.

# / -> {controller => 'foo', action => 'bar', mymessage => 'hi'}
$r->route('/:mymessage')
  ->to(controller => 'foo', action => 'bar', mymessage => 'hi');

This is also the case if multiple placeholders are right after another and not separated by other characters than /.

# /           -> {controller => 'foo',   action => 'bar'}
# /users      -> {controller => 'users', action => 'bar'}
# /users/list -> {controller => 'users', action => 'list'}
$r->route('/:controller/:action')
  ->to(controller => 'foo', action => 'bar');

Special stash values like controller and action can also be placeholders, this allows for extremely flexible routes constructs.

Named routes

Naming your routes will allow backreferencing in many kinds of helpers throughout the whole framework.

# /foo/abc -> {controller => 'foo', action => 'bar', name => 'abc'}
$r->route('/foo/:name')->name('test')
  ->to(controller => 'foo', action => 'bar');

# Generate URL "/foo/abc" for route "test"
$self->url_for('test');

# Generate URL "/foo/sebastian" for route "test"
$self->url_for('test', name => 'sebastian');

Nameless routes get an automatically generated one assigned that is simply equal to the route itself without non-word characters.

# /foo/bar ("foobar")
$r->route('/foo/bar')->to('test#stuff');

# Generate URL "/foo/bar"
$self->url_for('foobar');

To refer to the current route you can use the reserved name current or no name at all.

# Generate URL for current route
$self->url_for('current');
$self->url_for;

HTTP methods

The via method of the route object allows only specific HTTP methods to pass.

# GET /bye    -> {controller => 'foo', action => 'bye'}
# POST /bye   -> undef
# DELETE /bye -> undef
$r->route('/bye')->via('GET')->to(controller => 'foo', action => 'bye');

# GET /bye    -> {controller => 'foo', action => 'bye'}
# POST /bye   -> {controller => 'foo', action => 'bye'}
# DELETE /bye -> undef
$r->route('/bye')->via('GET', 'POST')
  ->to(controller => 'foo', action => 'bye');

Nested routes

It is also possible to build tree structures from routes to remove repetitive code. A route with children can't match on it's own though, only the actual endpoints of these nested routes can.

# /foo     -> undef
# /foo/bar -> {controller => 'foo', action => 'bar'}
my $foo = $r->route('/foo')->to(controller => 'foo');
$foo->route('/bar')->to(action => 'bar');

The stash will simply move from route to route and newer values override old ones.

# /foo     -> undef
# /foo/abc -> undef
# /foo/bar -> {controller => 'foo', action => 'bar'}
# /foo/baz -> {controller => 'foo', action => 'baz'}
# /foo/cde -> {controller => 'foo', action => 'abc'}
my $foo = $r->route('/foo')->to(controller => 'foo', action => 'abc');
$foo->route('/bar')->to(action => 'bar');
$foo->route('/baz')->to(action => 'baz');
$foo->route('/cde');

Waypoints

Waypoints are very similar to normal nested routes but can match even if they have children.

# /foo     -> {controller => 'foo', action => 'baz'}
# /foo/bar -> {controller => 'foo', action => 'bar'}
my $foo = $r->waypoint('/foo')->to(controller => 'foo', action => 'baz');
$foo->route('/bar')->to(action => 'bar');

All children will be ignored if a waypoint matches.

Bridges

Bridges unlike nested routes and waypoints always match and result in additional dispatch cycles.

# /foo     -> undef
# /foo/bar -> {controller => 'foo', action => 'baz'}
#             {controller => 'foo', action => 'bar'}
my $foo = $r->bridge('/foo')->to(controller => 'foo', action => 'baz');
$foo->route('/bar')->to(action => 'bar');

The actual bridge code needs to return a true value or the dispatch chain will be broken, this makes bridges a very powerful tool for authentication.

# /foo     -> undef
# /foo/bar -> {cb => sub {...}}
#             {controller => 'foo', action => 'bar'}
my $foo = $r->bridge('/foo')->to(cb => sub {
  my $self = shift;

  # Authenticated
  return 1 if $self->req->headers->header('X-Bender');

  # Not authenticated
  $self->render(text => "You're not Bender.");
  return;
});
$foo->route('/bar')->to(controller => 'foo', action => 'bar');

Mojolicious::Lite routes

Mojolicious::Lite routes are in fact just a small convenience layer around everything described above and also part of the normal router.

# GET /foo -> {controller => 'foo', action => 'abc'}
$r->get('/foo')->to(controller => 'foo', action => 'abc');

This makes the process of growing your Mojolicious::Lite prototypes into full Mojolicious applications very straightforward.

# POST /bar
$r->post('/bar' => sub {
  my $self = shift;
  $self->render(text => 'Just like a Mojolicious::Lite action.');
});

Even the more abstract concepts are available.

# GET  /yada
# POST /yada
my $yada = $r->under('/yada');
$yada->get(sub {
  my $self = shift;
  $self->render(text => 'Hello.');
});
$yada->post(sub {
  my $self = shift;
  $self->render(text => 'Go away.');
});

Shortcuts

You can also add your own shortcuts to make route generation more expressive.

# Simple "resource" shortcut
$r->add_shortcut(resource => sub {
  my ($r, $name) = @_;

  # Generate "/$name" route
  my $resource = $r->route("/$name")->to("$name#");

  # Handle POST requests
  $resource->post->to('#create')->name("create_$name");

  # Handle GET requests
  $resource->get->to('#show')->name("show_$name");

  return $resource;
});

# POST /user -> {controller => 'user', action => 'create'}
# GET  /user -> {controller => 'user', action => 'show'}
$r->resource('user');

Shortcuts can lead to anything, routes, bridges or maybe even both. And watch out for quicksand!

Introspection

The routes command can be used from the command line to list all available routes together with name and underlying regular expressions.

$ script/myapp routes -v
/foo/:name  GET   fooname  ^/foo/([^/\.]+))(?:\.([^/]+)$)?
/bar        POST  bar      ^/bar(?:\.([^/]+)$)?

ADVANCED

Less commonly used and more powerful features.

IRIs

IRIs are handled transparently, that means paths are guaranteed to be unescaped and decoded to Perl characters.

use utf8;

# /☃ (unicode snowman) -> {controller => 'foo', action => 'snowman'}
$r->route('/☃')->to(controller => 'foo', action => 'snowman');

Just don't forget to use the utf8 pragma or you'll make the unicode snowman very sad.

WebSockets

You can restrict access to WebSocket handshakes using the websocket method.

# /echo (WebSocket handshake)
$r->websocket('/echo')->to(controller => 'foo', action => 'echo');

# Controller
package MyApp::Foo;
use Mojo::Base 'Mojolicious::Controller';

# Action
sub echo {
  my $self = shift;
  $self->on(message => sub {
    my ($self, $message) = @_;
    $self->send_message("echo: $message");
  });
}

1;

Conditions

Sometimes you might need a little more power, for example to check the User-Agent header in multiple routes. This is where conditions come into play, they are basically router plugins.

# Simple "User-Agent" condition
$r->add_condition(
  agent => sub {
    my ($r, $c, $captures, $pattern) = @_;

    # User supplied regular expression
    return unless $pattern && ref $pattern eq 'Regexp';

    # Match "User-Agent" header and return true on success
    my $agent = $c->req->headers->user_agent;
    return 1 if $agent && $agent =~ $pattern;

    # No success
    return;
  }
);

# /firefox_only (Firefox) -> {controller => 'foo', action => 'bar'}
$r->route('/firefox_only')->over(agent => qr/Firefox/)
  ->to(controller => 'foo', action => 'bar');

The method add_condition registers the new condition in the router while over actually applies it to the route.

Condition plugins

You can also package your conditions as reusable plugins.

# Plugin
package Mojolicious::Plugin::WerewolfCondition;
use Mojo::Base 'Mojolicious::Plugin';

use Astro::MoonPhase;

sub register {
  my ($self, $app) = @_;

  # Add "werewolf" condition
  $app->routes->add_condition(
    werewolf => sub {
      my ($r, $c, $captures, $days) = @_;

      # Keep the werewolfs out!
      return if abs(14 - (phase(time))[2]) > ($days / 2);

      # It's ok, no werewolf
      return 1;
    }
  );
}

1;

Now just load the plugin and you are ready to use the condition in all your applications.

# Application
package MyApp;
use Mojo::Base 'Mojolicious';

sub startup {
  my $self = shift;

  # Plugin
  $self->plugin('WerewolfCondition');

  # Routes
  my $r = $self->routes;

  # /hideout (keep them out for 4 days after full moon)
  $r->route('/hideout')->over(werewolf => 4)
    ->to(controller => 'foo', action => 'bar');
}

1;

Embedding applications

You can easily embed whole applications simply by using them instead of a controller. This allows for example the use of the Mojolicious::Lite domain specific language in normal Mojolicious controllers.

# Controller
package MyApp::Bar;
use Mojolicious::Lite;

# /hello
get '/hello' => sub {
  my $self = shift;
  my $name = $self->param('name');
  $self->render(text => "Hello $name.");
};

1;

With the detour method which is very similar to to, you can allow the route to partially match and use only the remaining path in the embedded application.

# /foo/*
$r->route('/foo')->detour('bar#', name => 'Mojo');

A minimal embeddable application is nothing more than a subclass of Mojo, containing a handler method accepting Mojolicious::Controller objects.

package MyApp::Bar;
use Mojo::Base 'Mojo';

sub handler {
  my ($self, $c) = @_;
  $c->res->code(200);
  my $name = $c->param('name');
  $c->res->body("Hello $name.");
}

1;

You can also just use Mojolicious::Plugin::Mount to mount whole self-contained applications under a prefix.

use Mojolicious::Lite;

# Whole application mounted under "/prefix"
plugin Mount => {'/prefix' => '/home/sri/myapp.pl'};

# Normal route
get '/' => sub { shift->render_text('Hello World!') };

app->start;

Application plugins

Embedding Mojolicious applications is easy, but it gets even easier if you package the whole thing as a self contained reusable plugin.

# Plugin
package Mojolicious::Plugin::MyEmbeddedApp;
use Mojo::Base 'Mojolicious::Plugin';

sub register {
  my ($self, $app) = @_;

  # Automatically add route
  $app->routes->route('/foo')->detour(app => EmbeddedApp::app());
}

package EmbeddedApp;
use Mojolicious::Lite;

get '/bar' => 'bar';

1;
__DATA__
@@ bar.html.ep
Hello World!

The app stash value can be used for already instantiated applications. Now just load the plugin and you're done.

# Application
package MyApp;
use Mojo::Base 'Mojolicious';

sub startup {
  my $self = shift;

  # Plugin
  $self->plugin('MyEmbeddedApp');
}

1;

You can continue with Mojolicious::Guides now or take a look at the Mojolicious wiki http://github.com/kraih/mojo/wiki, which contains a lot more documentation and examples by many different authors.

To install Mojolicious, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Mojolicious

CPAN shell

perl -MCPAN -e shell
install Mojolicious

For more information on module installation, please visit the detailed CPAN module installation guide.

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