bionic (3) Mojolicious::Guides::Rendering.3pm.gz
NAME
Mojolicious::Guides::Rendering - Rendering content
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 "template.format.handler" scheme, with "template" defaulting to
"controller/action" or the route name, "format" defaulting to "html" and "handler" to "ep".
{controller => 'users', action => 'list'} -> 'users/list.html.ep'
{template => 'foo', format => 'txt'} -> 'foo.txt.ep'
{template => 'foo', handler => 'epl'} -> 'foo.html.epl'
The "controller" value gets converted from "CamelCase" to "snake_case" using "decamelize" in Mojo::Util
and "-" characters replaced with "/".
{controller => 'My::Users', action => 'add'} -> 'my/users/add.html.ep'
{controller => 'my-users', action => 'show'} -> 'my/users/show.html.ep'
All templates should be in the "templates" directories of the application, which can be customized with
"paths" in Mojolicious::Renderer, or one of the the "DATA" sections from "classes" in
Mojolicious::Renderer.
__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 is based on Mojo::Template and allows the embedding of Perl code right into actual
content using a small set of special tags and line start characters. For all templates strict, warnings,
utf8 and Perl 5.10 features are automatically enabled.
<% 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 =%>" (explained later)
%= 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.
<%= 'I ♥ Mojolicious!' %>
<%== '<p>I ♥ Mojolicious!</p>' %>
Only Mojo::ByteStream objects are excluded from automatic escaping.
<%= b('<p>I ♥ Mojolicious!</p>') %>
Whitespace characters around tags can be trimmed by adding an additional equal sign to the end of a tag.
<% for (1 .. 3) { %>
<%= 'Trim all whitespace characters around this expression' =%>
<% } %>
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
A newline character gets appended automatically to every template, unless the last character is a
backslash. And empty lines at the end of a template are ignored.
There is <%= 1 + 1 %> no newline at the end here\
At the beginning of the template, stash values that don't have invalid characters in their name get
automatically initialized as normal variables, and the controller object as both $self and $c.
$c->stash(name => 'tester');
Hello <%= $name %> from <%= $c->tx->remote_address %>.
A prefix like "myapp.*" is commonly used for stash values that you don't want to expose in templates.
$c->stash('myapp.name' => 'tester');
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.
$c->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.
$c->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.*.*
$c->render(template => 'foo/bar/baz');
Choosing a specific "format" and "handler" is just as easy.
# foo/bar/baz.txt.epl
$c->render(template => 'foo/bar/baz', format => 'txt', handler => 'epl');
Because rendering a specific template is the most common task it also has a shortcut.
$c->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.
$c->render_maybe('localized/baz') or $c->render('foo/bar/baz');
Rendering to strings
Sometimes you might want to use the rendered result directly instead of generating a response, for
example, to send emails, this can be done with "render_to_string" in Mojolicious::Controller.
my $html = $c->render_to_string('mail');
No encoding will be performed, making it easy to reuse the result in other templates or to generate
binary data.
my $pdf = $c->render_to_string('invoice', format => 'pdf');
$c->render(data => $pdf, format => 'pdf');
All arguments passed will get localized automatically and are only available during this render
operation.
Template variants
To make your application look great on many different devices you can also use the "variant" stash value
to choose between different variants of your templates.
# foo/bar/baz.html+phone.ep
# foo/bar/baz.html.ep
$c->render('foo/bar/baz', variant => 'phone');
This can be done very liberally since it only applies when a template with the correct name actually
exists and falls back to the generic one otherwise.
Rendering inline templates
Some renderers such as "ep" allow templates to be passed "inline".
$c->render(inline => 'The result is <%= 1 + 1 %>.');
Since auto-detection depends on a path you might have to supply a "handler" too.
$c->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 with "encoding" in Mojolicious::Renderer.
$c->render(text => 'I ♥ Mojolicious!');
Rendering data
Bytes can be rendered with the "data" stash value, no encoding will be performed.
$c->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.
$c->render(json => {foo => [1, 'test', 3]});
Status code
Response status codes can be changed with the "status" stash value.
$c->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
$c->render(text => 'Hello.', format => 'txt');
# Content-Type: image/png
$c->render(data => $bytes, format => 'png');
These mappings can be easily extended or changed with "types" in Mojolicious.
# Add new MIME type
$app->types->type(md => 'text/markdown');
Stash data
Any of the native Perl data types can be passed to templates as references through the "stash" in
Mojolicious::Controller.
$c->stash(description => 'web framework');
$c->stash(frameworks => ['Catalyst', 'Mojolicious']);
$c->stash(spinoffs => {minion => 'job queue'});
%= $description
%= $frameworks->[1]
%= $spinoffs->{minion}
Since everything is just Perl normal control structures just work.
% for my $framework (@$frameworks) {
<%= $framework %> is a <%= $description %>.
% }
% if (my $description = $spinoffs->{minion}) {
Minion is a <%= $description %>.
% }
For templates that might get rendered in different ways and where you're not sure if a stash value will
actually be set, you can just use the helper "stash" in Mojolicious::Plugin::DefaultHelpers.
% if (my $spinoffs = stash 'spinoffs') {
Minion is a <%= $spinoffs->{minion} %>.
% }
Helpers
Helpers are little functions you can use in templates as well as application and controller code.
# Template
%= dumper [1, 2, 3]
# Application
my $serialized = $app->dumper([1, 2, 3]);
# Controller
my $serialized = $c->dumper([1, 2, 3]);
We differentiate between default helpers, which are more general purpose like "dumper" in
Mojolicious::Plugin::DefaultHelpers, and tag helpers like "link_to" in Mojolicious::Plugin::TagHelpers,
which are template specific and mostly used to generate HTML tags.
%= link_to Mojolicious => 'http://mojolicious.org'
In controllers you can also use the method "helpers" in Mojolicious::Controller to fully qualify helper
calls and ensure that they don't conflict with existing methods you may already have.
my $serialized = $c->helpers->dumper([1, 2, 3]);
A list of all built-in helpers can be found in Mojolicious::Plugin::DefaultHelpers and
Mojolicious::Plugin::TagHelpers.
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"
$c->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.
$c->respond_to(
json => {json => {hello => 'world'}},
html => sub {
$c->content_for(head => '<meta name="author" content="sri">');
$c->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"
$c->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 = $c->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, which can be especially helpful during development. You can also render them manually
with the helpers "reply->exception" in Mojolicious::Plugin::DefaultHelpers and "reply->not_found" in
Mojolicious::Plugin::DefaultHelpers.
use Mojolicious::Lite;
use Scalar::Util 'looks_like_number';
get '/divide/:dividend/by/:divisor' => sub {
my $c = shift;
my $dividend = $c->param('dividend');
my $divisor = $c->param('divisor');
# 404
return $c->reply->not_found
unless looks_like_number $dividend && looks_like_number $divisor;
# 500
return $c->reply->exception('Division by zero!') if $divisor == 0;
# 200
$c->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.
use Mojolicious::Lite;
get '/dies' => sub { die 'Intentional error' };
app->start;
__DATA__
@@ 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 $snapshot %></pre>
</body>
</html>
The hook "before_render" in Mojolicious makes even more advanced customizations possible by allowing you
to intercept and modify the arguments passed to the renderer.
use Mojolicious::Lite;
hook before_render => sub {
my ($c, $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 => $args->{exception}} if $c->accepts('json');
};
get '/' => sub { die "This sho...ALL GLORY TO THE HYPNOTOAD!\n" };
app->start;
Layouts
Most of the time when using "ep" templates you will want to wrap your generated content in an HTML
skeleton, thanks to layouts that's absolutely trivial.
use Mojolicious::Lite;
get '/' => {template => 'foo/bar'};
app->start;
__DATA__
@@ 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.
use Mojolicious::Lite;
get '/' => {template => 'foo/bar'};
app->start;
__DATA__
@@ 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.
$c->render(template => 'mytemplate', layout => 'mylayout');
To set a "layout" stash value application-wide you can use "defaults" in Mojolicious.
$app->defaults(layout => 'mylayout');
Layouts can also be used with "render_to_string" in Mojolicious::Controller, but the "layout" value needs
to be passed as a render argument (not a stash value).
my $html = $c->render_to_string('reminder', layout => 'mail');
Partial templates
You can break up bigger templates into smaller, more manageable chunks. These partial templates can also
be shared with other templates. Just use the helper "include" in Mojolicious::Plugin::DefaultHelpers to
include one template into another.
use Mojolicious::Lite;
get '/' => {template => 'foo/bar'};
app->start;
__DATA__
@@ foo/bar.html.ep
<!DOCTYPE html>
<html>
%= include '_header', title => 'Howdy'
<body>Bar</body>
</html>
@@ _header.html.ep
<head><title><%= $title %></title></head>
You can name partial templates however you like, but a leading underscore is a commonly used naming
convention.
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, with the "begin" and "end" keywords. Just be aware that both
keywords are part of the surrounding tag and not actual Perl code, so there can only be whitespace after
"begin" and before "end".
use Mojolicious::Lite;
get '/' => 'welcome';
app->start;
__DATA__
@@ welcome.html.ep
<% my $block = begin %>
% my $name = shift;
Hello <%= $name %>.
<% end %>
<%= $block->('Wolfgang') %>
<%= $block->('Baerbel') %>
A naive translation of the template to Perl code could look like this.
my $output = '';
my $block = sub {
my $name = shift;
my $output = '';
$output .= 'Hello ';
$output .= xml_escape scalar + $name;
$output .= '.';
return Mojo::ByteStream->new($output);
};
$output .= xml_escape scalar + $block->('Wolfgang');
$output .= xml_escape scalar + $block->('Baerbel');
return $output;
While template blocks cannot be shared between templates, they are most commonly used to pass parts of a
template to helpers.
Adding helpers
You should always try to keep your actions small and reuse as much code as possible. Helpers make this
very easy, they get passed the current controller object as first argument, and you can use them to do
pretty much anything an action could do.
use Mojolicious::Lite;
helper debug => sub {
my ($c, $str) = @_;
$c->app->log->debug($str);
};
get '/' => sub {
my $c = shift;
$c->debug('Hello from an action!');
} => 'index';
app->start;
__DATA__
@@ index.html.ep
% debug 'Hello from a template!';
Helpers can also accept template blocks as last argument, this for example, allows very pleasant to use
tag helpers and filters. Wrapping the helper result into a Mojo::ByteStream object can prevent accidental
double escaping.
use Mojolicious::Lite;
use Mojo::ByteStream;
helper trim_newline => sub {
my ($c, $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
Similar to stash values, you can use a prefix like "myapp.*" to keep helpers from getting exposed in
templates as functions, and to organize them into namespaces as your application grows. Every prefix
automatically becomes a helper that returns a proxy object containing the current controller object and
on which you can call the nested helpers.
use Mojolicious::Lite;
helper 'cache_control.no_caching' => sub {
my $c = shift;
$c->res->headers->cache_control('private, max-age=0, no-cache');
};
helper 'cache_control.five_minutes' => sub {
my $c = shift;
$c->res->headers->cache_control('public, max-age=300');
};
get '/news' => sub {
my $c = shift;
$c->cache_control->no_caching;
$c->render(text => 'Always up to date.');
};
get '/some_older_story' => sub {
my $c = shift;
$c->cache_control->five_minutes;
$c->render(text => 'This one can be cached for a bit.');
};
app->start;
While helpers can also be redefined, this should only be done very carefully to avoid conflicts.
Content blocks
The helper "content_for" in Mojolicious::Plugin::DefaultHelpers allows you to pass whole blocks of
content from one template to another. This can be very useful when your layout has distinct sections,
such as sidebars, where content should be inserted by the template.
use Mojolicious::Lite;
get '/' => 'foo';
app->start;
__DATA__
@@ foo.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 'header' %></head>
<body><%= content %></body>
</html>
Forms
To build HTML forms more efficiently you can use tag helpers like "form_for" in
Mojolicious::Plugin::TagHelpers, which can automatically select a request method for you if a route name
is provided. And since most browsers only allow forms to be submitted with "GET" and "POST", but not
request methods like "PUT" or "DELETE", they are spoofed with an "_method" query parameter.
use Mojolicious::Lite;
get '/' => 'form';
# PUT /nothing
# POST /nothing?_method=PUT
put '/nothing' => sub {
my $c = shift;
# Prevent double form submission with redirect
my $value = $c->param('whatever');
$c->flash(confirmation => "We did nothing with your value ($value).");
$c->redirect_to('form');
};
app->start;
__DATA__
@@ form.html.ep
<!DOCTYPE html>
<html>
<body>
% if (my $confirmation = flash 'confirmation') {
<p><%= $confirmation %></p>
% }
%= form_for nothing => begin
%= text_field whatever => 'I ♥ Mojolicious!'
%= submit_button
% end
</body>
</html>
The methods "flash" in Mojolicious::Controller and "redirect_to" in Mojolicious::Controller are often
used together to prevent double form submission, allowing users to receive a confirmation message that
will vanish if they decide to reload the page they've been redirected to.
Form validation
You can use "validation" in Mojolicious::Controller to validate "GET" and "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 $c = shift;
# Check if parameters have been submitted
my $validation = $c->validation;
return $c->render unless $validation->has_data;
# Validate parameters ("pass_again" depends on "pass")
$validation->required('user')->size(1, 20)->like(qr/^[a-z0-9]+$/);
$validation->required('pass_again')->equal_to('pass')
if $validation->optional('pass')->size(7, 500)->is_valid;
# Render confirmation if validation was successful
$c->render('thanks') unless $validation->has_error;
} => 'index';
app->start;
__DATA__
@@ index.html.ep
<!DOCTYPE html>
<html>
<head>
<style>
label.field-with-error { color: #dd7e5e }
input.field-with-error { background-color: #fd9e7e }
</style>
</head>
<body>
%= form_for index => begin
%= label_for user => 'Username (required, 1-20 characters, a-z/0-9)'
<br>
%= text_field 'user', id => 'user'
%= submit_button
<br>
%= label_for pass => 'Password (optional, 7-500 characters)'
<br>
%= password_field 'pass', id => 'pass'
<br>
%= label_for pass_again => 'Password again (equal to the value above)'
<br>
%= password_field 'pass_again', id => 'pass_again'
% end
</body>
</html>
@@ thanks.html.ep
<!DOCTYPE html>
<html><body>Thank you <%= validation->param('user') %>.</body></html>
Form elements generated with tag helpers from Mojolicious::Plugin::TagHelpers will automatically remember
their previous values and add the class "field-with-error" for fields that failed validation to make
styling with CSS easier.
<label class="field-with-error" for="user">
Username (required, only characters e-t)
</label>
<input class="field-with-error" type="text" name="user" value="sri">
For a full list of available checks see also "CHECKS" in Mojolicious::Validator.
Adding form validation checks
Validation checks can be registered with "add_check" in Mojolicious::Validator and return a false value
if they were successful. A true value may be used to pass along additional information which can then be
retrieved with "error" in Mojolicious::Validator::Validation.
use Mojolicious::Lite;
# Add "range" check
app->validator->add_check(range => sub {
my ($validation, $name, $value, $min, $max) = @_;
return $value < $min || $value > $max;
});
get '/' => 'form';
post '/test' => sub {
my $c = shift;
# Validate parameters with custom check
my $validation = $c->validation;
$validation->required('number')->range(3, 23);
# Render form again if validation failed
return $c->render('form') if $validation->has_error;
# Prevent double form submission with redirect
$c->flash(number => $validation->param('number'));
$c->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, with something as mundane as a link. 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 $c = shift;
# Check CSRF token
my $validation = $c->validation;
return $c->render(text => 'Bad CSRF token!', status => 403)
if $validation->csrf_protect->has_error('csrf_token');
my $city = $validation->required('city')->param('city');
$c->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', id => 'city'
%= submit_button
%= end
</body>
</html>
For Ajax requests and the like, you can also generate a token directly with the helper "csrf_token" in
Mojolicious::Plugin::DefaultHelpers, and then pass it along with the "X-CSRF-Token" request header.
ADVANCED
Less commonly used and more powerful features.
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 skeleton templates with named blocks that child templates can override.
use Mojolicious::Lite;
# first > mylayout
get '/first' => {template => 'first', layout => 'mylayout'};
# third > second > first > mylayout
get '/third' => {template => 'third', layout => 'mylayout'};
app->start;
__DATA__
@@ layouts/mylayout.html.ep
<!DOCTYPE html>
<html>
<head><title>Hello</title></head>
<body><%= content %></body>
</html>
@@ first.html.ep
%= content header => begin
Default header
% end
<div>Hello World!</div>
%= content footer => begin
Default footer
% end
@@ second.html.ep
% extends 'first';
% content header => begin
New header
% end
@@ third.html.ep
% extends 'second';
% content footer => begin
New footer
% end
This chain could go on and on to allow a very high level of template reuse.
Serving static files
Static files are automatically served from the "public" directories of the application, which can be
customized with "paths" in Mojolicious::Static, or one of the "DATA" sections from "classes" in
Mojolicious::Static. And if that's not enough you can also serve them manually with "reply->static" in
Mojolicious::Plugin::DefaultHelpers.
use Mojolicious::Lite;
get '/' => sub {
my $c = shift;
$c->reply->static('index.html');
};
get '/some_download' => sub {
my $c = shift;
$c->res->headers->content_disposition('attachment; filename=bar.png;');
$c->reply->static('foo/bar.png');
};
app->start;
Custom responses
Most response content, static as well as dynamic, gets served through Mojo::Asset::File and
Mojo::Asset::Memory objects. For somewhat static content, like cached JSON data or temporary files, you
can create your own and use the helper "reply->asset" in Mojolicious::Plugin::DefaultHelpers to serve
them while allowing content negotiation to be performed with "Range", "If-Modified-Since" and
"If-None-Match" headers.
use Mojolicious::Lite;
use Mojo::Asset::File;
get '/leak' => sub {
my $c = shift;
$c->res->headers->content_type('text/plain');
$c->reply->asset(Mojo::Asset::File->new(path => '/etc/passwd'));
};
app->start;
For even more control you can also just skip the helper and use "rendered" in Mojolicious::Controller to
tell the renderer when you're done generating a response.
use Mojolicious::Lite;
use Mojo::Asset::File;
get '/leak' => sub {
my $c = shift;
$c->res->headers->content_type('text/plain');
$c->res->content->asset(Mojo::Asset::File->new(path => '/etc/passwd'));
$c->rendered(200);
};
app->start;
Helper plugins
Some helpers might be useful enough for you to share them between multiple applications, plugins make
that very simple.
package Mojolicious::Plugin::DebugHelper;
use Mojo::Base 'Mojolicious::Plugin';
sub register {
my ($self, $app) = @_;
$app->helper(debug => sub {
my ($c, $str) = @_;
$c->app->log->debug($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 $c = shift;
$c->debug('It works!');
$c->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 Mojolicious-Plugin-AlertAssets/lib/Mojolicious/Plugin/AlertAssets
$ cd Mojolicious-Plugin-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 give them reasonably unique names, ideally based on the name of your plugin, and append their
respective directories to the list of search paths when "register" is called.
package Mojolicious::Plugin::AlertAssets;
use Mojo::Base 'Mojolicious::Plugin';
use Mojo::File 'path';
sub register {
my ($self, $app) = @_;
# Append "templates" and "public" directories
my $base = path(__FILE__)->sibling('AlertAssets');
push @{$app->renderer->paths}, $base->child('templates')->to_string;
push @{$app->static->paths}, $base->child('public')->to_string;
}
1;
Both will work just like normal "templates" and "public" directories once you've installed and loaded the
plugin, with slightly lower precedence.
use Mojolicious::Lite;
plugin 'AlertAssets';
get '/alert_me';
app->start;
__DATA__
@@ alert_me.html.ep
<!DOCTYPE html>
<html>
<head>
<title>Alert me!</title>
%= include 'alertassets'
</head>
<body>You've been alerted.</body>
</html>
And it works just the same for assets bundled in the "DATA" section of your plugin.
package Mojolicious::Plugin::AlertAssets;
use Mojo::Base 'Mojolicious::Plugin';
sub register {
my ($self, $app) = @_;
# Append class
push @{$app->renderer->classes}, __PACKAGE__;
push @{$app->static->classes}, __PACKAGE__;
}
1;
__DATA__
@@ alertassets.js
alert("Hello World!");
@@ alertassets.html.ep
%= javascript "/alertassets.js"
Post-processing dynamic content
While post-processing tasks are generally very easy with the hook "after_dispatch" in Mojolicious, for
content generated by the renderer it is a lot more efficient to use "after_render" in Mojolicious.
use Mojolicious::Lite;
use IO::Compress::Gzip 'gzip';
hook after_render => sub {
my ($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>
Streaming
You don't have to render all content at once, the method "write" in Mojolicious::Controller can also be
used to stream a series of smaller chunks.
use Mojolicious::Lite;
get '/' => sub {
my $c = shift;
# Prepare body
my $body = 'Hello World!';
$c->res->headers->content_length(length $body);
# Start writing directly with a drain callback
my $drain;
$drain = sub {
my $c = shift;
my $chunk = substr $body, 0, 1, '';
$drain = undef unless length $body;
$c->write($chunk, $drain);
};
$c->$drain;
};
app->start;
The drain callback will be executed whenever the entire previous chunk of data has actually been written.
HTTP/1.1 200 OK
Date: Sat, 13 Sep 2014 16:48:29 GMT
Content-Length: 12
Server: Mojolicious (Perl)
Hello World!
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.
use Mojolicious::Lite;
get '/' => sub {
my $c = shift;
$c->write_chunk('<html><head><title>Example</title></head>' => sub {
my $c = shift;
$c->finish('<body>Example</body></html>');
});
};
app->start;
The optional drain callback ensures that all previous chunks have been written before processing
continues. To end the stream you can call "finish" in Mojolicious::Controller or write an empty chunk of
data.
HTTP/1.1 200 OK
Date: Sat, 13 Sep 2014 16:48:29 GMT
Transfer-Encoding: chunked
Server: Mojolicious (Perl)
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.
$app->renderer->encoding('koi8-r');
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 ♥ 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.
use Mojolicious::Lite;
get '/' => {text => 'I ♥ Mojolicious!'};
app->start;
__DATA__
@@ 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", which is provided by
Mojolicious::Plugin::EPRenderer, and there is not already a plugin on CPAN for your favorite one. All you
have to do, is to 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_template = $options->{inline};
# Check for appropriate template in "templates" directories
my $template_path = $renderer->template_path($options);
# Check for appropriate template in DATA sections
my $data_template = $renderer->get_data_template($options);
# This part is up to you and your template system :)
...
# Pass the rendered result back to the renderer
$$output = 'Hello World!';
# Or just die if an error occurs
die 'Something went wrong with the template';
});
}
1;
An "inline" template, if provided by the user, will be passed along with the options. You can use
"template_path" in Mojolicious::Renderer to search the "templates" directories of the application, and
"get_data_template" in Mojolicious::Renderer to search the "DATA" sections.
use Mojolicious::Lite;
plugin 'MyRenderer';
# Render an inline template
get '/inline' => {inline => '...', handler => 'mine'};
# Render a template from the DATA section
get '/data' => {template => 'test'};
app->start;
__DATA__
@@ test.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 Storable 'nfreeze';
# Add "storable" handler
app->renderer->add_handler(storable => sub {
my ($renderer, $c, $output, $options) = @_;
# Disable automatic encoding
delete $options->{encoding};
# Encode data from stash value
$$output = nfreeze delete $c->stash->{storable};
});
# Set "handler" value automatically if "storable" value is set already
app->hook(before_render => sub {
my ($c, $args) = @_;
$args->{handler} = 'storable'
if exists $args->{storable} || exists $c->stash->{storable};
});
get '/' => {storable => {i => '♥ mojolicious'}};
app->start;
The hook "before_render" in Mojolicious can be used to make stash values like "storable" special, so that
they no longer require a "handler" value to be set explicitly.
# Explicit "handler" value
$c->render(storable => {i => '♥ mojolicious'}, handler => 'storable');
# Implicit "handler" value (with "before_render" hook)
$c->render(storable => {i => '♥ mojolicious'});
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>).