Mojolicious::Guides::Rendering(3)

NAME
Mojolicious::Guides::Rendering - Rendering

OVERVIEW
This document explains content generation with the Mojolicious renderer.

CONCEPTS
Essentials every Mojolicious developer should know.

  Renderer
The renderer is a tiny black box turning stash data into actual responses utilizing multiple template systems and data encoding modules.

  {text => 'Hello.'}                 -> 200 OK, text/html, 'Hello.'
  {json => {x => 3}}                 -> 200 OK, application/json, '{"x":3}'
  {text => 'Oops.', status => '410'} -> 410 Gone, text/html, 'Oops.'

Templates can be automatically detected if enough information is provided by the developer or routes. Template names are expected to follow the "name.format.handler" scheme, with "name" defaulting to "controller/action" or the route name, "format" defaulting to "html" and "handler" to "ep".

  {controller => 'users', action => 'list'} -> 'users/list.html.ep'
  {name => 'foo', format => 'txt'}          -> 'foo.txt.ep'
  {name => 'foo', handler => 'epl'}         -> 'foo.html.epl'

All templates should be in the "templates" directories of the application or the "DATA" section of the class "main".

  __DATA__

  @@ time.html.ep
  % use Time::Piece;
  % my $now = localtime;
  <!DOCTYPE html>
  <html>
    <head><title>Time</title></head>
    <body>The time is <%= $now->hms %>.</body>
  </html>

  @@ hello.txt.ep
  ...

The renderer can be easily extended to support additional template systems with plugins, but more about that later.

  Embedded Perl
Mojolicious includes a minimalistic but very powerful template system out of the box called Embedded Perl or "ep" for short. It allows the embedding of Perl code right into actual content using a small set of special tags and line start characters.

  <% Perl code %>
  <%= Perl expression, replaced with XML escaped result %>
  <%== Perl expression, replaced with result %>
  <%# Comment, useful for debugging %>
  <%% Replaced with "<%", useful for generating templates %>
  % Perl code line, treated as "<% line =%>"
  %= Perl expression line, treated as "<%= line %>"
  %== Perl expression line, treated as "<%== line %>"
  %# Comment line, useful for debugging
  %% Replaced with "%", useful for generating templates

Tags and lines work pretty much the same, but depending on context one will usually look a bit better. Semicolons get automatically appended to all expressions.

  <% my $i = 10; %>
  <ul>
    <% for my $j (1 .. $i) { %>
      <li>
        <%= $j %>
      </li>
    <% } %>
  </ul>

  % my $i = 10;
  <ul>
    % for my $j (1 .. $i) {
      <li>
        %= $j
      </li>
    % }
  </ul>

Aside from differences in whitespace handling, both examples generate similar Perl code, a naive translation could look like this.

  my $output = '';
  my $i = 10;
  $output .= '<ul>';
  for my $j (1 .. $i) {
    $output .= '<li>';
    $output .= xml_escape scalar $j;
    $output .= '</li>';
  }
  $output .= '</ul>';
  return $output;

An additional equal sign can be used to disable escaping of the characters "<", ">", "&", "'" and """ in results from Perl expressions, which is the default to prevent XSS attacks against your application.

  <%= 'lalala' %>
  <%== '<p>test</p>' %>

Only Mojo::ByteStream objects are excluded from automatic escaping.

  <%= b('<p>test</p>') %>

Newline characters can be escaped with a backslash.

  This is <%= 1 + 1 %> a\
  single line

And a backslash in front of a newline character can be escaped with another backslash.

  This will <%= 1 + 1 %> result\\
  in multiple\\
  lines

You can also add an additional equal sign to the end of a tag to have it automatically remove all surrounding whitespace, this allows you to freely indent your code without ruining the result.

  <% for (1 .. 3) { %>
    <%= $foo =%>
  <% } %>

Stash values that don't have invalid characters in their name get automatically initialized as normal variables in the template, and the controller object as $self.

  $self->stash(name => 'tester');

  Hello <%= $name %> from <%= $self->tx->remote_address %>.

There are also many helper functions available, but more about that later.

  <%= dumper {foo => 'bar'} %>

BASICS
Most commonly used features every Mojolicious developer should know about.

  Automatic rendering
The renderer can be manually started by calling the method "render" in Mojolicious::Controller, but that's usually not necessary, because it will get automatically called if nothing has been rendered after the router finished its work. This also means you can have routes pointing only to templates without actual actions.

  $self->render;

There is one big difference though, by calling it manually you can make sure that templates use the current controller object, and not the default controller specified with the attribute "controller_class" in Mojolicious.

  $self->render_later;

You can also disable automatic rendering with the method "render_later" in Mojolicious::Controller, which can be very useful to delay rendering when a non-blocking operation has to be performed first.

  Rendering templates
The renderer will always try to detect the right template, but you can also use the "template" stash value to render a specific one. Everything before the last slash will be interpreted as the subdirectory path in which to find the template.

  # foo/bar/baz.*.*
  $self->render(template => 'foo/bar/baz');

Choosing a specific "format" and "handler" is just as easy.

  # foo/bar/baz.txt.epl
  $self->render(template => 'foo/bar/baz', format => 'txt', handler => 'epl');

Because rendering a specific template is the most common task it also has a shortcut.

  $self->render('foo/bar/baz');

If you're not sure in advance if a template actually exists, you can also use the method "render_maybe" in Mojolicious::Controller to try multiple alternatives.

  $self->render_maybe('localized/baz') or $self->render('foo/bar/baz');

  Rendering inline templates
Some renderers such as "ep" allow templates to be passed inline.

  $self->render(inline => 'The result is <%= 1 + 1 %>.');

Since auto detection depends on a path you might have to supply a "handler" too.

  $self->render(inline => "<%= shift->param('foo') %>", handler => 'epl');

  Rendering text
Characters can be rendered to bytes with the "text" stash value, the given content will be automatically encoded to bytes.

  $self->render(text => 'I X Mojolicious!');

  Rendering data
Bytes can be rendered with the "data" stash value, no encoding will be performed.

  $self->render(data => $bytes);

  Rendering JSON
The "json" stash value allows you to pass Perl data structures to the renderer which get directly encoded to JSON with Mojo::JSON.

  $self->render(json => {foo => [1, 'test', 3]});

  Partial rendering
Sometimes you might want to use the rendered result directly instead of generating a response, for example to send emails, this can be done using the "partial" render argument (not the stash value).

  my $html = $self->render('mail', partial => 1);

No encoding will be performed, making it easy to reuse the result in other templates or to generate binary data.

  my $pdf = $self->render('invoice', format => 'pdf', partial => 1);
  $self->render(data => $pdf, format => 'pdf');

  Status code
Response status codes can be changed with the "status" stash value.

  $self->render(text => 'Oops.', status => 500);

  Content type
The "Content-Type" header of the response is actually based on the MIME type mapping of the "format" stash value.

  # Content-Type: text/plain
  $self->render(text => 'Hello.', format => 'txt');

  # Content-Type: image/png
  $self->render(data => $bytes, format => 'png');

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

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

  sub startup {
    my $self = shift;

    # Add new MIME type
    $self->types->type(txt => 'text/plain; charset=utf-8');
  }

  1;

  Stash data
Any of the native Perl data types can be passed to templates through the "stash" in Mojolicious::Controller.

  $self->stash(author     => 'Sebastian');
  $self->stash(frameworks => [qw(Catalyst Mojolicious)]);
  $self->stash(examples   => {tweetylicious => 'a microblogging app'});

  %= $author
  %= $frameworks->[1]
  %= $examples->{tweetylicious}

Since everything is just Perl normal control structures just work.

  % for my $framework (@$frameworks) {
    <%= $framework %> was written by <%= $author %>.
  % }

  % while (my ($app, $description) = each %$examples) {
    <%= $app %> is a <%= $description %>.
  % }

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

  # /hello (Accept: application/json) -> "json"
  # /hello (Accept: application/xml)  -> "xml"
  # /hello.json                       -> "json"
  # /hello.xml                        -> "xml"
  # /hello?format=json                -> "json"
  # /hello?format=xml                 -> "xml"
  $self->respond_to(
    json => {json => {hello => 'world'}},
    xml  => {text => '<hello>world</hello>'}
  );

The best possible representation will be automatically selected from the "Accept" request header, "format" stash value or "format" GET/POST parameter and stored in the "format" stash value. To change MIME type mappings for the "Accept" request header or the "Content-Type" response header you can use "types" in Mojolicious.

  $self->respond_to(
    json => {json => {hello => 'world'}},
    html => sub {
      $self->content_for(head => '<meta name="author" content="sri">');
      $self->render(template => 'hello', message => 'world')
    }
  );

Callbacks can be used for representations that are too complex to fit into a single render call.

  # /hello (Accept: application/json) -> "json"
  # /hello (Accept: text/html)        -> "html"
  # /hello (Accept: image/png)        -> "any"
  # /hello.json                       -> "json"
  # /hello.html                       -> "html"
  # /hello.png                        -> "any"
  # /hello?format=json                -> "json"
  # /hello?format=html                -> "html"
  # /hello?format=png                 -> "any"
  $self->respond_to(
    json => {json => {hello => 'world'}},
    html => {template => 'hello', message => 'world'},
    any  => {text => '', status => 204}
  );

And if no viable representation could be found, the "any" fallback will be used or an empty 204 response rendered automatically.

  # /hello                      -> "html"
  # /hello (Accept: text/html)  -> "html"
  # /hello (Accept: text/xml)   -> "xml"
  # /hello (Accept: text/plain) -> undef
  # /hello.html                 -> "html"
  # /hello.xml                  -> "xml"
  # /hello.txt                  -> undef
  # /hello?format=html          -> "html"
  # /hello?format=xml           -> "xml"
  # /hello?format=txt           -> undef
  if (my $format = $self->accepts('html', 'xml')) {
    ...
  }

For even more advanced negotiation logic you can also use the helper "accepts" in Mojolicious::Plugin::DefaultHelpers.

  Rendering "exception" and "not_found" pages
By now you've probably already encountered the built-in 404 (Not Found) and 500 (Server Error) pages, that get rendered automatically when you make a mistake. Those are fallbacks for when your own exception handling fails, but especially during development they can also be a great help, you can render them manually with the methods "render_exception" in Mojolicious::Controller and "render_not_found" in Mojolicious::Controller.

  use Mojolicious::Lite;
  use Scalar::Util 'looks_like_number';

  get '/divide/:dividend/by/:divisor' => sub {
    my $self = shift;
    my ($dividend, $divisor) = $self->param(['dividend', 'divisor']);

    # 404
    return $self->render_not_found
      unless looks_like_number $dividend && looks_like_number $divisor;

    # 500
    return $self->render_exception('Division by zero!') if $divisor == 0;

    # 200
    $self->render(text => $dividend / $divisor);
  };

  app->start;

You can also change the templates of those pages, since you most likely want to show your users something more closely related to your application in production. The renderer will always try to find "exception.$mode.$format.*" or "not_found.$mode.$format.*" before falling back to the built-in default templates.

  @@ exception.production.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Server error</title></head>
    <body>
      <h1>Exception</h1>
      <p><%= $exception->message %></p>
      <h1>Stash</h1>
      <pre><%= dumper $snapshot %></pre>
    </body>
  </html>

The hook "before_render" in Mojolicious makes even more advanced customizations possible by allowing you to intercept and modify the arguments passed to the renderer.

  use Mojolicious::Lite;

  hook before_render => sub {
    my ($self, $args) = @_;

    # Make sure we are rendering the exception template
    return unless my $template = $args->{template};
    return unless $template eq 'exception';

    # Switch to JSON rendering if content negotiation allows it
    $args->{json} = {exception => $self->stash('exception')}
      if $self->accepts('json');
  };

  get '/' => sub { die "This sho...ALL GLORY TO THE HYPNOTOAD!\n" };

  app->start;

  Helpers
Helpers are little functions you can use in templates and controller code.

  %= dumper [1, 2, 3]

  my $serialized = $self->dumper([1, 2, 3]);

The helper "dumper" in Mojolicious::Plugin::DefaultHelpers for example will use Data::Dumper to serialize whatever data structure you pass it, this can be very useful for debugging. We differentiate between "default helpers" which are more general purpose like "dumper" and "tag helpers", which are template specific and mostly used to generate "HTML" tags.

  %= javascript '/script.js'

  %= javascript begin
    var a = 'b';
  % end

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

  Layouts
Most of the time when using "ep" templates you will want to wrap your generated content in a HTML skeleton, thanks to layouts that's absolutely trivial.

  @@ foo/bar.html.ep
  % layout 'mylayout';
  Hello World!

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

You just select the right layout template with the helper "layout" in Mojolicious::Plugin::DefaultHelpers and place the result of the current template with the helper "content" in Mojolicious::Plugin::DefaultHelpers. You can also pass along normal stash values to the "layout" helper.

  @@ foo/bar.html.ep
  % layout 'mylayout', title => 'Hi there';
  Hello World!

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

Instead of the "layout" helper you could also just use the "layout" stash value, or call "render" in Mojolicious::Controller with the "layout" argument.

  $self->render(template => 'mytemplate', layout => 'mylayout');

To set a "layout" stash value application wide you can use "defaults" in Mojolicious.

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

  sub startup {
    my $self = shift;

    # Default layout
    $self->defaults(layout => 'mylayout');
  }

  1;

Layouts can also be used with "partial" templates, but the "layout" value needs to be passed as a render argument (not a stash value).

  my $html = $self->render('reminder', layout => 'mail', partial => 1);

  Including partial templates
Like most helpers "include" in Mojolicious::Plugin::DefaultHelpers is just a shortcut to make your life a little easier.

  @@ foo/bar.html.ep
  <!DOCTYPE html>
  <html>
    %= include 'header'
    <body>Bar</body>
  </html>

  @@ header.html.ep
  <head><title>Howdy</title></head>

Instead of "include" you could also just call "render" in Mojolicious::Controller with the "partial" argument.

  @@ foo/bar.html.ep
  <!DOCTYPE html>
  <html>
    %= $self->render('header', partial => 1)
    <body>Bar</body>
  </html>

  @@ header.html.ep
  <head><title>Howdy</title></head>

But there is one small difference between the two, if you pass stash values to "include", they will get localized automatically and are only available in the partial template.

  @@ foo/bar.html.ep
  <!DOCTYPE html>
  <html>
    %= include 'header', title => 'Hello'
    <body>Bar</body>
  </html>

  @@ header.html.ep
  <head><title><%= $title %></title></head>

  Reusable template blocks
It's never fun to repeat yourself, that's why you can build reusable template blocks in "ep" that work very similar to normal Perl functions.

  @@ welcome.html.ep
  <% my $block = begin %>
    <% my $name = shift; %>
    Hello <%= $name %>.
  <% end %>
  <%= $block->('Sebastian') %>
  <%= $block->('Sara') %>

Blocks are always delimited by the "begin" and "end" keywords.

  @@ welcome.html.ep
  % my $block = begin
    % my $name = shift;
    Hello <%= $name %>.
  % end
  % for (1 .. 10) {
    %== $block->('Sebastian')
  % }

A naive translation to Perl code could look like this.

  @@ welcome.html.pl
  my $output = '';
  my $block  = sub {
    my $name   = shift;
    my $output = '';
    $output .= 'Hello ';
    $output .= xml_escape scalar $name;
    $output .= '.';
    return Mojo::ByteStream->new($output);
  }
  for (1 .. 10) {
    $output .= scalar $block->('Sebastian');
  }
  return $output;

  Content blocks
Blocks and the helper "content_for" in Mojolicious::Plugin::DefaultHelpers can also be used to pass whole sections of the template to the layout.

  @@ foo/bar.html.ep
  % layout 'mylayout';
  % content_for header => begin
    <meta http-equiv="Content-Type" content="text/html">
  % end
  <div>Hello World!</div>
  % content_for header => begin
    <meta http-equiv="Pragma" content="no-cache">
  % end

  @@ layouts/mylayout.html.ep
  <!DOCTYPE html>
  <html>
    <head><%= content_for 'header' %></head>
    <body><%= content %></body>
  </html>

  Template inheritance
Inheritance takes the layout concept above one step further, the helpers "content" in Mojolicious::Plugin::DefaultHelpers and "extends" in Mojolicious::Plugin::DefaultHelpers allow you to build a skeleton template with named blocks that child templates can override.

  @@ first.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Hello</title></head>
    <body>
      %= content header => begin
        Default header
      % end
      <div>Hello World!</div>
      %= content footer => begin
        Default footer
      % end
    </body>
  </html>

  @@ second.html.ep
  % extends 'first';
  % content header => begin
    New header
  % end

This chain could go on and on to allow a very high level of template reuse.

  Form validation
You can use "validation" in Mojolicious::Controller to validate GET/POST parameters submitted to your application. All unknown fields will be ignored by default, so you have to decide which should be required or optional before you can perform checks on their values. Every check is performed right away, so you can use the results immediately to build more advanced validation logic with methods like "is_valid" in Mojolicious::Validator::Validation.

  use Mojolicious::Lite;

  get '/' => sub {
    my $self = shift;

    # Check if parameters have been submitted
    my $validation = $self->validation;
    return $self->render unless $validation->has_data;

    # Validate parameters ("pass_again" depends on "pass")
    $validation->required('user')->size(1, 20)->like(qr/^[e-t]+$/);
    $validation->required('pass_again')->equal_to('pass')
      if $validation->optional('pass')->size(7, 500)->is_valid;

    # Render confirmation if validation was successful
    $self->render('thanks') unless $validation->has_error;
  } => 'index';

  app->start;
  __DATA__

  @@ index.html.ep
  <!DOCTYPE html>
  <html>
    <head>
      %= stylesheet begin
        label.field-with-error { color: #dd7e5e }
        input.field-with-error { background-color: #fd9e7e }
      % end
    </head>
    <body>
      %= form_for index => begin
        %= label_for user => 'Username (required, 1-20 characters, only e-t)'
        <br>
        %= text_field 'user'
        %= submit_button
        <br>
        %= label_for pass => 'Password (optional, 7-500 characters)'
        <br>
        %= password_field 'pass'
        <br>
        %= label_for pass_again => 'Password again (equal to the value above)'
        <br>
        %= password_field 'pass_again'
      % end
    </body>
  </html>

  @@ thanks.html.ep
  <!DOCTYPE html>
  <html><body>Thank you <%= validation->param('user') %>.</body></html>

Form elements generated with tag helpers from Mojolicious::Plugin::TagHelpers will automatically remember their previous values and add the class "field-with-error" for fields that failed validation to make styling with CSS easier.

  <label class="field-with-error" for="user">
    Username (required, only characters e-t)
  </label>
  <input class="field-with-error" type="text" name="user" value="sri" />

For a full list of available checks see also "CHECKS" in Mojolicious::Validator.

  Adding form validation checks
Validation checks can be registered with "add_check" in Mojolicious::Validator and return a false value if they were successful. A true value may be used to pass along additional information which can then be retrieved with "error" in Mojolicious::Validator::Validation.

  use Mojolicious::Lite;

  # Add "range" check
  app->validator->add_check(range => sub {
    my ($validation, $name, $value, $min, $max) = @_;
    return $value < $min || $value > $max;
  });

  get '/' => 'form';

  post '/test' => sub {
    my $self = shift;

    # Validate parameters with custom check
    my $validation = $self->validation;
    $validation->required('number')->range(3, 23);

    # Render form again if validation failed
    return $self->render('form') if $validation->has_error;

    # Prevent double submit with redirect
    $self->flash(number => $validation->param('number'));
    $self->redirect_to('form');
  };

  app->start;
  __DATA__

  @@ form.html.ep
  <!DOCTYPE html>
  <html>
    <body>
      % if (my $number = flash 'number') {
        <p>Thanks, the number <%= $number %> was valid.</p>
      % }
      %= form_for test => begin
        % if (my $err = validation->error('number')) {
          <p>
            %= 'Value is required.' if $err->[0] eq 'required'
            %= 'Value needs to be between 3 and 23.' if $err->[0] eq 'range'
          </p>
        % }
        %= text_field 'number'
        %= submit_button
      % end
    </body>
  </html>

  Cross-site request forgery
CSRF is a very common attack on web applications that trick your logged in users to submit forms they did not intend to send. All you have to do to protect your users from this, is to add an additional hidden field to your forms with "csrf_field" in Mojolicious::Plugin::TagHelpers and validate it with "csrf_protect" in Mojolicious::Validator::Validation.

  use Mojolicious::Lite;

  get '/' => {template => 'target'};

  post '/' => sub {
    my $self = shift;

    # Check CSRF token
    my $validation = $self->validation;
    return $self->render(text => 'Bad CSRF token!', status => 403)
      if $validation->csrf_protect->has_error('csrf_token');

    my $city = $validation->required('city')->param('city');
    $self->render(text => "Low orbit ion cannon pointed at $city!")
      unless $validation->has_error;
  } => 'target';

  app->start;
  __DATA__

  @@ target.html.ep
  <!DOCTYPE html>
  <html>
    <body>
      %= form_for target => begin
        %= csrf_field
        %= label_for city => 'Which city to point low orbit ion cannon at?'
        %= text_field 'city'
        %= submit_button
      %= end
    </body>
  </html>

The token can also be submitted with the "X-CSRF-Token" request header.

  Adding helpers
Adding and redefining helpers is very easy, you can use them to do pretty much everything.

  use Mojolicious::Lite;

  helper debug => sub {
    my ($self, $str) = @_;
    $self->app->log->debug($str);
  };

  get '/' => sub {
    my $self = shift;
    $self->debug('Hello from an action!');
  } => 'index';

  app->start;
  __DATA__

  @@ index.html.ep
  % debug 'Hello from a template!';

Helpers can also accept template blocks as last argument, this for example allows very pleasant to use tag helpers and filters.

  use Mojolicious::Lite;
  use Mojo::ByteStream;

  helper trim_newline => sub {
    my ($self, $block) = @_;
    my $result = $block->();
    $result =~ s/\n//g;
    return Mojo::ByteStream->new($result);
  };

  get '/' => 'index';

  app->start;
  __DATA__

  @@ index.html.ep
  %= trim_newline begin
    Some text.
    %= 1 + 1
    More text.
  % end

Wrapping the helper result into a Mojo::ByteStream object can prevent accidental double escaping.

  Helper plugins
Some helpers might be useful enough for you to share them between multiple applications, plugins make that very simple.

  package Mojolicious::Plugin::DebugHelper;
  use Mojo::Base 'Mojolicious::Plugin';

  sub register {
    my ($self, $app) = @_;
    $app->helper(debug => sub {
      my ($self, $str) = @_;
      $self->app->log->debug($str);
    });
  }

  1;

The "register" method will be called when you load the plugin and to add your helper to the application you can use "helper" in Mojolicious.

  use Mojolicious::Lite;

  plugin 'DebugHelper';

  get '/' => sub {
    my $self = shift;
    $self->debug('It works.');
    $self->render(text => 'Hello.');
  };

  app->start;

A skeleton for a full CPAN compatible plugin distribution can be automatically generated.

  $ mojo generate plugin DebugHelper

And if you have a "PAUSE" account (which can be requested at <http://pause.perl.org>), you are only a few commands away from releasing it to CPAN.

  $ perl Makefile.PL
  $ make test
  $ make manifest
  $ make dist
  $ mojo cpanify -u USER -p PASS Mojolicious-Plugin-DebugHelper-0.01.tar.gz

  Bundling assets with plugins
Assets such as templates and static files can be easily bundled with your plugins, even if you plan to release them to CPAN.

  $ mojo generate plugin AlertAssets
  $ mkdir AlertAssets/lib/Mojolicious/Plugin/AlertAssets
  $ cd AlertAssets/lib/Mojolicious/Plugin/AlertAssets
  $ mkdir public
  $ echo 'alert("Hello World!");' > public/alertassets.js
  $ mkdir templates
  $ echo '%= javascript "/alertassets.js"' > templates/alertassets.html.ep

Just append their respective directories to the list of search paths when "register" is called.

  package Mojolicious::Plugin::AlertAssets;
  use Mojo::Base 'Mojolicious::Plugin';

  use File::Basename 'dirname';
  use File::Spec::Functions 'catdir';

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

    # Append "templates" and "public" directories
    my $base = catdir(dirname(__FILE__), 'AlertAssets');
    push @{$app->renderer->paths}, catdir($base, 'templates');
    push @{$app->static->paths},   catdir($base, 'public');
  }

  1;

Both will work just like normal "templates" and "public" directories once you've installed and loaded the plugin, with slightly lower precedence.

  use Mojolicious::Lite;

  plugin 'AlertAssets';

  get '/alert_me';

  app->start;
  __DATA__

  @@ alert_me.html.ep
  <!DOCTYPE html>
  <html>
    <head>
      <title>Alert me!</title>
      %= include 'alertassets'
    </head>
    <body>You've been alerted.</body>
  </html>

And it works just the same for assets bundled in the "DATA" section of your plugin.

  package Mojolicious::Plugin::AlertAssets;
  use Mojo::Base 'Mojolicious::Plugin';

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

    # Append class
    push @{$app->renderer->classes}, __PACKAGE__;
    push @{$app->static->classes},   __PACKAGE__;
  }

  1;
  __DATA__

  @@ alertassets.js
  alert("Hello World!");

  @@ alertassets.html.ep
  %= javascript "/alertassets.js"

ADVANCED
Less commonly used and more powerful features.

  Rendering static files
If automatic rendering of static files is not enough, you can also render them manually from your "DATA" sections and "public" directories with "render_static" in Mojolicious::Controller.

  $self->res->headers->content_disposition('attachment; filename=bar.png;');
  $self->render_static('foo/bar.png');

  Custom responses
For entirely custom responses to, for example, stream content directly from files, you can use "rendered" in Mojolicious::Controller to tell the renderer that a response has been generated.

  $self->res->headers->content_type('text/plain');
  $self->res->content->asset(Mojo::Asset::File->new(path => '/etc/passwd'));
  $self->rendered(200);

  Post-processing dynamic content
While post-processing tasks are generally very easy with the hook "after_dispatch" in Mojolicious, for content generated by the renderer it is a lot more efficient to use "after_render" in Mojolicious.

  use Mojolicious::Lite;
  use IO::Compress::Gzip 'gzip';

  hook after_render => sub {
    my ($c, $output, $format) = @_;

    # Check if "gzip => 1" has been set in the stash
    return unless $c->stash->{gzip};

    # Check if user agent accepts GZip compression
    return unless ($c->req->headers->accept_encoding // '') =~ /gzip/i;
    $c->res->headers->append(Vary => 'Accept-Encoding');

    # Compress content with GZip
    $c->res->headers->content_encoding('gzip');
    gzip $output, \my $compressed;
    $$output = $compressed;
  };

  get '/' => {template => 'hello', title => 'Hello', gzip => 1};

  app->start;
  __DATA__

  @@ hello.html.ep
  <!DOCTYPE html>
  <html>
    <head><title><%= title %></title></head>
    <body>Compressed content.</body>
  </html>

  Chunked transfer encoding
For very dynamic content you might not know the response content length in advance, that's where the "chunked" transfer encoding and "write_chunk" in Mojolicious::Controller come in handy. A common use would be to send the "head" section of an HTML document to the browser in advance and speed up preloading of referenced images and stylesheets.

  $self->write_chunk('<html><head><title>Example</title></head>' => sub {
    my $self = shift;
    $self->finish('<body>Example</body></html>');
  });

The optional drain callback ensures that all previous chunks have been written before processing continues. An empty chunk or call to "finish" in Mojolicious::Controller marks the end of the stream.

  29
  <html><head><title>Example</title></head>
  1b
  <body>Example</body></html>
  0

Especially in combination with long inactivity timeouts this can be very useful for Comet (long polling). Due to limitations in some web servers this might not work perfectly in all deployment environments.

  Encoding
Templates stored in files are expected to be "UTF-8" by default, but that can be easily changed with "encoding" in Mojolicious::Renderer.

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

  sub startup {
    my $self = shift;

    # Different encoding
    $self->renderer->encoding('koi8-r');
  }

  1;

All templates from the "DATA" section are bound to the encoding of the Perl script.

  use Mojolicious::Lite;

  get '/heart';

  app->start;

  __DATA__
  @@ heart.html.ep
  I X Mojolicious!

  Base64 encoded DATA files
Base64 encoded static files such as images can be easily stored in the "DATA" section of your application, similar to templates.

  @@ favicon.ico (base64)
  ...base64 encoded image...

  Inflating DATA templates
Templates stored in files get preferred over files from the "DATA" section, this allows you to include a default set of templates in your application that the user can later customize. The command Mojolicious::Command::inflate will write all templates and static files from the "DATA" section into actual files in the "templates" and "public" directories.

  $ ./myapp.pl inflate

  Customizing the template syntax
You can easily change the whole template syntax by loading Mojolicious::Plugin::EPRenderer with a custom configuration.

  use Mojolicious::Lite;

  plugin EPRenderer => {
    name     => 'mustache',
    template => {
      tag_start => '{{',
      tag_end   => '}}'
    }
  };

  get '/:name' => {name => 'Anonymous'} => 'index';

  app->start;
  __DATA__

  @@ index.html.mustache
  Hello {{= $name }}.

Mojo::Template contains the whole list of available options.

  Adding your favorite template system
Maybe you would prefer a different template system than "ep", and there is not already a plugin on CPAN for your favorite one, all you have to do is add a new "handler" with "add_handler" in Mojolicious::Renderer when "register" is called.

  package Mojolicious::Plugin::MyRenderer;
  use Mojo::Base 'Mojolicious::Plugin';

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

    # Add "mine" handler
    $app->renderer->add_handler(mine => sub {
      my ($renderer, $c, $output, $options) = @_;

      # Check for one-time use inline template
      my $inline = $options->{inline};

      # Check for absolute template path
      my $path = $renderer->template_path($options);

      # Check for appropriate template in DATA section
      my $data = $renderer->get_data_template($options);

      # This part is up to you and your template system :)
      ...

      # Just die if an error occurs
      die 'Something went wrong';

      # Or pass the rendered result back to the renderer
      $$output = 'Hello World!';

      # And return true if something has been rendered or false otherwise
      return 1;
    });
  }

  1;

Since most template systems don't support templates in the "DATA" section, the renderer provides methods to help you with that.

  use Mojolicious::Lite;

  plugin 'MyRenderer';

  get '/' => 'index';

  app->start;
  __DATA__

  @@ index.html.mine
  ...

  Adding a handler to generate binary data
By default the renderer assumes that every "handler" generates characters that need to be automatically encoded, but this can be easily disabled if you're generating bytes instead.

  use Mojolicious::Lite;
  use Mango::BSON ':bson';

  # Add "bson" handler
  app->renderer->add_handler(bson => sub {
    my ($renderer, $c, $output, $options) = @_;

    # Disable automatic encoding
    delete $options->{encoding};

    # Encode BSON data from stash value
    $$output = bson_encode delete $c->stash->{bson};

    return 1;
  });

  get '/' => {bson => {i => 'X mojolicious'}, handler => 'bson'};

  app->start;

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".