Mojolicious::Guides::Tutorial(3)

NAME
Mojolicious::Guides::Tutorial - Get started with Mojolicious

TUTORIAL
A quick example-driven introduction to the wonders of Mojolicious::Lite. Almost everything you'll learn here also applies to full Mojolicious applications.

This is only the first of the Mojolicious::Guides. Other guides delve deeper into topics like growing a Mojolicious::Lite prototype into a well-structured Mojolicious application, routing, rendering and more. It is highly encouraged that readers continue on to the remaining guides after reading this one.

  Hello World
A simple Hello World application can look like this, strict, warnings, utf8 and Perl 5.10 features are automatically enabled and a few functions imported, when you use Mojolicious::Lite, turning your script into a full featured web application.

  #!/usr/bin/env perl
  use Mojolicious::Lite;

  get '/' => sub {
    my $c = shift;
    $c->render(text => 'Hello World!');
  };

  app->start;

With Mojolicious::Command::generate::lite_app there is also a helper command to generate a small example application.

  $ mojo generate lite_app myapp.pl

  Commands
Many different commands are automatically available from the command line. CGI and PSGI environments can even be detected and will usually just work without commands.

  $ ./myapp.pl daemon
  Server available at http://127.0.0.1:3000

  $ ./myapp.pl daemon -l http://*:8080
  Server available at http://127.0.0.1:8080

  $ ./myapp.pl cgi
  ...CGI output...

  $ ./myapp.pl get /
  Hello World!

  $ ./myapp.pl
  ...List of available commands (or automatically detected environment)...

A call to "start" in Mojolicious ("app->start"), which starts the command system, should be the last expression in your application, because its return value can be significant.

  # Use @ARGV to pick a command
  app->start;

  # Start the "daemon" command
  app->start('daemon', '-l', 'http://*:8080');

  Reloading
Your application will automatically reload itself if you start it with the morbo development web server, so you don't have to restart the server after every change.

  $ morbo ./myapp.pl
  Server available at http://127.0.0.1:3000

For more information about how to deploy your application see also "DEPLOYMENT" in Mojolicious::Guides::Cookbook.

  Routes
Routes are basically just fancy paths that can contain different kinds of placeholders and usually lead to an action, if they match the path part of the request URL. The first argument passed to all actions ($c) is a Mojolicious::Controller object, containing both the HTTP request and response.

  use Mojolicious::Lite;

  # Route leading to an action that renders some text
  get '/foo' => sub {
    my $c = shift;
    $c->render(text => 'Hello World!');
  };

  app->start;

Response content is often generated by actions with "render" in Mojolicious::Controller, but more about that later.

  GET/POST parameters
All "GET" and "POST" parameters sent with the request are accessible via "param" in Mojolicious::Controller.

  use Mojolicious::Lite;

  # /foo?user=sri
  get '/foo' => sub {
    my $c    = shift;
    my $user = $c->param('user');
    $c->render(text => "Hello $user.");
  };

  app->start;

  Stash and templates
The "stash" in Mojolicious::Controller is used to pass data to templates, which can be inlined in the "DATA" section. A few stash values like "template", "text" and "data" are reserved and will be used by "render" in Mojolicious::Controller to decide how a response should be generated.

  use Mojolicious::Lite;

  # Route leading to an action that renders a template
  get '/foo' => sub {
    my $c = shift;
    $c->stash(one => 23);
    $c->render(template => 'magic', two => 24);
  };

  app->start;
  __DATA__

  @@ magic.html.ep
  The magic numbers are <%= $one %> and <%= $two %>.

For more information about templates see also "Embedded Perl" in Mojolicious::Guides::Rendering.

  HTTP
"req" in Mojolicious::Controller and "res" in Mojolicious::Controller give you full access to all HTTP features and information.

  use Mojolicious::Lite;

  # Access request information
  get '/agent' => sub {
    my $c    = shift;
    my $host = $c->req->url->to_abs->host;
    my $ua   = $c->req->headers->user_agent;
    $c->render(text => "Request by $ua reached $host.");
  };

  # Echo the request body and send custom header with response
  post '/echo' => sub {
    my $c = shift;
    $c->res->headers->header('X-Bender' => 'Bite my shiny metal ass!');
    $c->render(data => $c->req->body);
  };

  app->start;

You can test the more advanced examples right from the command line with Mojolicious::Command::get.

  $ ./myapp.pl get -v -M POST -c 'test' /echo

  JSON
JSON is the most commonly used data-interchange format for web services. Mojolicious loves JSON and comes with the possibly fastest pure-Perl implementation Mojo::JSON built right in, which is accessible through "json" in Mojo::Message as well as the reserved stash value "json".

  use Mojolicious::Lite;

  # Modify the received JSON document and return it
  put '/reverse' => sub {
    my $c    = shift;
    my $hash = $c->req->json;
    $hash->{message} = reverse $hash->{message};
    $c->render(json => $hash);
  };

  app->start;

You can send JSON documents from the command line with Mojolicious::Command::get.

  $ ./myapp.pl get -M PUT -c '{"message":"Hello Mojo!"}' /reverse

  Built-in "exception" and "not_found" pages
During development you will encounter these pages whenever you make a mistake, they are gorgeous and contain a lot of valuable information that will aid you in debugging your application.

  use Mojolicious::Lite;

  # Not found (404)
  get '/missing' => sub { shift->render(template => 'does_not_exist') };

  # Exception (500)
  get '/dies' => sub { die 'Intentional error' };

  app->start;

You can even use CSS selectors with Mojolicious::Command::get to extract only the information you're actually interested in.

  $ ./myapp.pl get /dies '#error'

And don't worry about revealing too much information on these pages, they are only available during development, and will be replaced automatically with pages that don't reveal any sensitive information in a production environment.

  Route names
All routes can have a name associated with them, this allows automatic template detection and backreferencing with "url_for" in Mojolicious::Controller, on which many methods and helpers like "link_to" in Mojolicious::Plugin::TagHelpers rely.

  use Mojolicious::Lite;

  # Render the template "index.html.ep"
  get '/' => sub {
    my $c = shift;
    $c->render;
  } => 'index';

  # Render the template "hello.html.ep"
  get '/hello';

  app->start;
  __DATA__

  @@ index.html.ep
  <%= link_to Hello  => 'hello' %>.
  <%= link_to Reload => 'index' %>.

  @@ hello.html.ep
  Hello World!

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

  Layouts
Templates can have layouts too, you just select one with the helper "layout" in Mojolicious::Plugin::DefaultHelpers and place the result of the current template with the helper "content" in Mojolicious::Plugin::DefaultHelpers.

  use Mojolicious::Lite;

  get '/with_layout';

  app->start;
  __DATA__

  @@ with_layout.html.ep
  % title 'Green';
  % layout 'green';
  Hello World!

  @@ layouts/green.html.ep
  <!DOCTYPE html>
  <html>
    <head><title><%= title %></title></head>
    <body><%= content %></body>
  </html>

The stash or helpers like "title" in Mojolicious::Plugin::DefaultHelpers can be used to pass additional data to the layout.

  Blocks
Template blocks can be used like normal Perl functions and are always delimited by the "begin" and "end" keywords, they are the foundation for many helpers.

  use Mojolicious::Lite;

  get '/with_block' => 'block';

  app->start;
  __DATA__

  @@ block.html.ep
  % my $link = begin
    % my ($url, $name) = @_;
    Try <%= link_to $url => begin %><%= $name %><% end %>.
  % end
  <!DOCTYPE html>
  <html>
    <head><title>Sebastians frameworks</title></head>
    <body>
      %= $link->('http://mojolicious.org', 'Mojolicious')
      %= $link->('http://catalystframework.org', 'Catalyst')
    </body>
  </html>

  Helpers
Helpers are little functions you can create with the keyword "helper" in Mojolicious::Lite and reuse throughout your whole application, from actions to templates.

  use Mojolicious::Lite;

  # A helper to identify visitors
  helper whois => sub {
    my $c     = shift;
    my $agent = $c->req->headers->user_agent || 'Anonymous';
    my $ip    = $c->tx->remote_address;
    return "$agent ($ip)";
  };

  # Use helper in action and template
  get '/secret' => sub {
    my $c    = shift;
    my $user = $c->whois;
    $c->app->log->debug("Request from $user");
  };

  app->start;
  __DATA__

  @@ secret.html.ep
  We know who you are <%= whois %>.

A list of all built-in ones can be found in Mojolicious::Plugin::DefaultHelpers and Mojolicious::Plugin::TagHelpers.

  Placeholders
Route placeholders allow capturing parts of a request path until a "/" or "." separator occurs, similar to the regular expression "([^/.]+)". Results are accessible via "stash" in Mojolicious::Controller and "param" in Mojolicious::Controller.

  use Mojolicious::Lite;

  # /foo/test
  # /foo/test123
  get '/foo/:bar' => sub {
    my $c   = shift;
    my $bar = $c->stash('bar');
    $c->render(text => "Our :bar placeholder matched $bar");
  };

  # /testsomething/foo
  # /test123something/foo
  get '/(:bar)something/foo' => sub {
    my $c   = shift;
    my $bar = $c->param('bar');
    $c->render(text => "Our :bar placeholder matched $bar");
  };

  app->start;

To separate them from the surrounding text, you can surround your placeholders with parentheses, which also makes the colon prefix optional.

  Relaxed Placeholders
Relaxed placeholders allow matching of everything until a "/" occurs, similar to the regular expression "([^/]+)".

  use Mojolicious::Lite;

  # /hello/test
  # /hello/test.html
  get '/hello/#you' => 'groovy';

  app->start;
  __DATA__

  @@ groovy.html.ep
  Your name is <%= $you %>.

  Wildcard placeholders
Wildcard placeholders allow matching absolutely everything, including "/" and ".", similar to the regular expression "(.+)".

  use Mojolicious::Lite;

  # /hello/test
  # /hello/test123
  # /hello/test.123/test/123
  get '/hello/*you' => 'groovy';

  app->start;
  __DATA__

  @@ groovy.html.ep
  Your name is <%= $you %>.

  HTTP methods
Routes can be restricted to specific request methods with different keywords like "get" in Mojolicious::Lite and "any" in Mojolicious::Lite.

  use Mojolicious::Lite;

  # GET /hello
  get '/hello' => sub {
    my $c = shift;
    $c->render(text => 'Hello World!');
  };

  # PUT /hello
  put '/hello' => sub {
    my $c    = shift;
    my $size = length $c->req->body;
    $c->render(text => "You uploaded $size bytes to /hello.");
  };

  # GET|POST|PATCH /bye
  any ['GET', 'POST', 'PATCH'] => '/bye' => sub {
    my $c = shift;
    $c->render(text => 'Bye World!');
  };

  # * /whatever
  any '/whatever' => sub {
    my $c      = shift;
    my $method = $c->req->method;
    $c->render(text => "You called /whatever with $method.");
  };

  app->start;

  Optional placeholders
All placeholders require a value, but by assigning them default values you can make capturing optional.

  use Mojolicious::Lite;

  # /hello
  # /hello/Sara
  get '/hello/:name' => {name => 'Sebastian', day => 'Monday'} => sub {
    my $c = shift;
    $c->render(template => 'groovy', format => 'txt');
  };

  app->start;
  __DATA__

  @@ groovy.txt.ep
  My name is <%= $name %> and it is <%= $day %>.

Default values that don't belong to a placeholder simply get merged into the stash all the time.

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

  use Mojolicious::Lite;

  # /test
  # /123
  any '/:foo' => [foo => ['test', '123']] => sub {
    my $c   = shift;
    my $foo = $c->param('foo');
    $c->render(text => "Our :foo placeholder matched $foo");
  };

  app->start;

All placeholders get compiled to a regular expression internally, this process can also be customized. Just make sure not to use "^" and "$", or capturing groups "(...)", non-capturing groups "(?:...)" are fine though.

  use Mojolicious::Lite;

  # /1
  # /123
  any '/:bar' => [bar => qr/\d+/] => sub {
    my $c   = shift;
    my $bar = $c->param('bar');
    $c->render(text => "Our :bar placeholder matched $bar");
  };

  app->start;

You can take a closer look at all the generated regular expressions with the command Mojolicious::Command::routes.

  $ ./myapp.pl routes -v

  Under
Authentication and code shared between multiple routes can be realized easily with routes generated by "under" in Mojolicious::Lite. All following routes are only evaluated if the callback returned a true value.

  use Mojolicious::Lite;

  # Authenticate based on name parameter
  under sub {
    my $c = shift;

    # Authenticated
    my $name = $c->param('name') || '';
    return 1 if $name eq 'Bender';

    # Not authenticated
    $c->render(template => 'denied');
    return undef;
  };

  # Only reached when authenticated
  get '/' => 'index';

  app->start;
  __DATA__

  @@ denied.html.ep
  You are not Bender, permission denied.

  @@ index.html.ep
  Hi Bender.

Prefixing multiple routes is another good use for it.

  use Mojolicious::Lite;

  # /foo
  under '/foo';

  # /foo/bar
  get '/bar' => {text => 'foo bar'};

  # /foo/baz
  get '/baz' => {text => 'foo baz'};

  # / (reset)
  under '/' => {msg => 'whatever'};

  # /bar
  get '/bar' => {inline => '<%= $msg %> works'};

  app->start;

You can also group related routes with "group" in Mojolicious::Lite, which allows nesting of routes generated with "under" in Mojolicious::Lite.

  use Mojolicious::Lite;

  # Global logic shared by all routes
  under sub {
    my $c = shift;
    return 1 if $c->req->headers->header('X-Bender');
    $c->render(text => "You're not Bender.");
    return undef;
  };

  # Admin section
  group {

    # Local logic shared only by routes in this group
    under '/admin' => sub {
      my $c = shift;
      return 1 if $c->req->headers->header('X-Awesome');
      $c->render(text => "You're not awesome enough.");
      return undef;
    };

    # GET /admin/dashboard
    get '/dashboard' => {text => 'Nothing to see here yet.'};
  };

  # GET /welcome
  get '/welcome' => {text => 'Hi Bender.'};

  app->start;

  Formats
Formats can be automatically detected from file extensions like ".html", they are used to find the right template and generate the correct "Content-Type" header.

  use Mojolicious::Lite;

  # /detection
  # /detection.html
  # /detection.txt
  get '/detection' => sub {
    my $c = shift;
    $c->render(template => 'detected');
  };

  app->start;
  __DATA__

  @@ detected.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Detected</title></head>
    <body>HTML was detected.</body>
  </html>

  @@ detected.txt.ep
  TXT was detected.

The default format is "html", and restrictive placeholders can be used to limit possible values.

  use Mojolicious::Lite;

  # /hello.json
  # /hello.txt
  get '/hello' => [format => ['json', 'txt']] => sub {
    my $c = shift;
    return $c->render(json => {hello => 'world'})
      if $c->stash('format') eq 'json';
    $c->render(text => 'hello world');
  };

  app->start;

Or you can just disable format detection with a special type of restrictive placeholder.

  use Mojolicious::Lite;

  # /hello
  get '/hello' => [format => 0] => {text => 'No format detection.'};

  # Disable detection and allow the following routes to re-enable it on demand
  under [format => 0];

  # /foo
  get '/foo' => {text => 'No format detection again.'};

  # /bar.txt
  get '/bar' => [format => 'txt'] => {text => ' Just one format.'};

  app->start;

  Content negotiation
For resources with different representations and that require truly RESTful content negotiation you can also use "respond_to" in Mojolicious::Controller.

  use Mojolicious::Lite;

  # /hello (Accept: application/json)
  # /hello (Accept: application/xml)
  # /hello.json
  # /hello.xml
  # /hello?format=json
  # /hello?format=xml
  get '/hello' => sub {
    my $c = shift;
    $c->respond_to(
      json => {json => {hello => 'world'}},
      xml  => {text => '<hello>world</hello>'},
      any  => {data => '', status => 204}
    );
  };

  app->start;

MIME type mappings can be extended or changed easily with "types" in Mojolicious.

  app->types->type(rdf => 'application/rdf+xml');

  Static files
Similar to templates, but with only a single file extension and optional Base64 encoding, static files can be inlined in the "DATA" section and are served automatically.

  use Mojolicious::Lite;

  app->start;
  __DATA__

  @@ something.js
  alert('hello!');

  @@ test.txt (base64)
  dGVzdCAxMjMKbGFsYWxh

External static files are not limited to a single file extension and will be served automatically from a "public" directory if it exists.

  $ mkdir public
  $ mv something.js public/something.js
  $ mv mojolicious.tar.gz public/mojolicious.tar.gz

Both have a higher precedence than routes for "GET" and "HEAD" requests. Content negotiation with "Range", "If-None-Match" and "If-Modified-Since" headers is supported as well and can be tested very easily with Mojolicious::Command::get.

  $ ./myapp.pl get /something.js -v -H 'Range: bytes=2-4'

  External templates
External templates will be searched by the renderer in a "templates" directory if it exists.

  $ mkdir -p templates/foo
  $ echo 'Hello World!' > templates/foo/bar.html.ep

They have a higher precedence than templates in the "DATA" section.

  use Mojolicious::Lite;

  # Render template "templates/foo/bar.html.ep"
  any '/external' => sub {
    my $c = shift;
    $c->render(template => 'foo/bar');
  };

  app->start;

  Conditions
Conditions such as "agent" and "host" from Mojolicious::Plugin::HeaderCondition allow even more powerful route constructs.

  use Mojolicious::Lite;

  # Firefox
  get '/foo' => (agent => qr/Firefox/) => sub {
    my $c = shift;
    $c->render(text => 'Congratulations, you are using a cool browser.');
  };

  # Internet Explorer
  get '/foo' => (agent => qr/Internet Explorer/) => sub {
    my $c = shift;
    $c->render(text => 'Dude, you really need to upgrade to Firefox.');
  };

  # http://mojolicious.org/bar
  get '/bar' => (host => 'mojolicious.org') => sub {
    my $c = shift;
    $c->render(text => 'Hello Mojolicious.');
  };

  app->start;

  Sessions
Cookie-based sessions just work out of the box, as soon as you start using them through the helper "session" in Mojolicious::Plugin::DefaultHelpers. Just be aware that all session data gets serialized with Mojo::JSON and stored client-side, with a cryptographic signature to prevent tampering.

  use Mojolicious::Lite;

  # Access session data in action and template
  get '/counter' => sub {
    my $c = shift;
    $c->session->{counter}++;
  };

  app->start;
  __DATA__

  @@ counter.html.ep
  Counter: <%= session 'counter' %>

Note that you should use custom "secrets" in Mojolicious to make signed cookies really tamper resistant.

  app->secrets(['My secret passphrase here']);

  File uploads
All files uploaded via "multipart/form-data" request are automatically available as Mojo::Upload objects from "param" in Mojolicious::Controller. And you don't have to worry about memory usage, because all files above 250KB will be automatically streamed into a temporary file. To build HTML forms more efficiently, you can also use tag helpers like "form_for" in Mojolicious::Plugin::TagHelpers.

  use Mojolicious::Lite;

  # Upload form in DATA section
  get '/' => 'form';

  # Multipart upload handler
  post '/upload' => sub {
    my $c = shift;

    # Check file size
    return $c->render(text => 'File is too big.', status => 200)
      if $c->req->is_limit_exceeded;

    # Process uploaded file
    return $c->redirect_to('form') unless my $example = $c->param('example');
    my $size = $example->size;
    my $name = $example->filename;
    $c->render(text => "Thanks for uploading $size byte file $name.");
  };

  app->start;
  __DATA__

  @@ form.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Upload</title></head>
    <body>
      %= form_for upload => (enctype => 'multipart/form-data') => begin
        %= file_field 'example'
        %= submit_button 'Upload'
      % end
    </body>
  </html>

To protect you from excessively large files there is also a limit of 16MB by default, which you can tweak with the attribute "max_request_size" in Mojolicious.

  # Increase limit to 1GB
  app->max_request_size(1073741824);

  User agent
With Mojo::UserAgent, which is available through the helper "ua" in Mojolicious::Plugin::DefaultHelpers, there's a full featured HTTP and WebSocket user agent built right in. Especially in combination with Mojo::JSON and Mojo::DOM this can be a very powerful tool.

  use Mojolicious::Lite;

  # Blocking
  get '/headers' => sub {
    my $c   = shift;
    my $url = $c->param('url') || 'http://mojolicious.org';
    my $dom = $c->ua->get($url)->result->dom;
    $c->render(json => $dom->find('h1, h2, h3')->map('text')->to_array);
  };

  # Non-blocking
  get '/title' => sub {
    my $c = shift;
    $c->ua->get('mojolicious.org' => sub {
      my ($ua, $tx) = @_;
      $c->render(data => $tx->result->dom->at('title')->text);
    });
  };

  # Concurrent non-blocking
  get '/titles' => sub {
    my $c = shift;
    $c->delay(
      sub {
        my $delay = shift;
        $c->ua->get('http://mojolicious.org' => $delay->begin);
        $c->ua->get('https://metacpan.org'   => $delay->begin);
      },
      sub {
        my ($delay, $mojo, $cpan) = @_;
        $c->render(json => {
          mojo => $mojo->result->dom->at('title')->text,
          cpan => $cpan->result->dom->at('title')->text
        });
      }
    );
  };

  app->start;

For more information about the user agent see also "USER AGENT" in Mojolicious::Guides::Cookbook.

  WebSockets
WebSocket applications have never been this simple before. Just receive messages by subscribing to events such as "json" in Mojo::Transaction::WebSocket with "on" in Mojolicious::Controller and return them with "send" in Mojolicious::Controller.

  use Mojolicious::Lite;

  websocket '/echo' => sub {
    my $c = shift;
    $c->on(json => sub {
      my ($c, $hash) = @_;
      $hash->{msg} = "echo: $hash->{msg}";
      $c->send({json => $hash});
    });
  };

  get '/' => 'index';

  app->start;
  __DATA__

  @@ index.html.ep
  <!DOCTYPE html>
  <html>
    <head>
      <title>Echo</title>
      <script>
        var ws = new WebSocket('<%= url_for('echo')->to_abs %>');
        ws.onmessage = function (event) {
          document.body.innerHTML += JSON.parse(event.data).msg;
        };
        ws.onopen = function (event) {
          ws.send(JSON.stringify({msg: 'I ♥ Mojolicious!'}));
        };
      </script>
    </head>
  </html>

For more information about real-time web features see also "REAL-TIME WEB" in Mojolicious::Guides::Cookbook.

  Mode
You can use the Mojo::Log object from "log" in Mojo to portably collect debug messages and automatically disable them later in a production setup by changing the Mojolicious operating mode, which can also be retrieved from the attribute "mode" in Mojolicious.

  use Mojolicious::Lite;

  # Prepare mode specific message during startup
  my $msg = app->mode eq 'development' ? 'Development!' : 'Something else!';

  get '/' => sub {
    my $c = shift;
    $c->app->log->debug('Rendering mode specific message');
    $c->render(text => $msg);
  };

  app->log->debug('Starting application');
  app->start;

The default operating mode will usually be "development" and can be changed with command line options or the "MOJO_MODE" and "PLACK_ENV" environment variables. A mode other than "development" will raise the log level from "debug" to "info".

  $ ./myapp.pl daemon -m production

All messages will be written to "STDERR" or a "log/$mode.log" file if a "log" directory exists.

  $ mkdir log

Mode changes also affect a few other aspects of the framework, such as the built-in "exception" and "not_found" pages. Once you switch modes from "development" to "production", no sensitive information will be revealed on those pages anymore.

  Testing
Testing your application is as easy as creating a "t" directory and filling it with normal Perl tests like "t/basic.t", which can be a lot of fun thanks to Test::Mojo.

  use Test::More;
  use Test::Mojo;

  use FindBin;
  require "$FindBin::Bin/../myapp.pl";

  my $t = Test::Mojo->new;
  $t->get_ok('/')->status_is(200)->content_like(qr/Funky/);

  done_testing();

Just run your tests with the command Mojolicious::Command::test or prove.

  $ ./myapp.pl test
  $ ./myapp.pl test -v t/basic.t
  $ prove -l -v t/basic.t

MORE
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.

SUPPORT
If you have any questions the documentation might not yet answer, don't hesitate to ask on the mailing list <http://groups.google.com/group/mojolicious> or the official IRC channel "#mojo" on "irc.perl.org" (chat now! <https://chat.mibbit.com/?channel=%23mojo&server=irc.perl.org>).