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, treated as "<%# line =%>"
%% 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.
<%= Mojo::ByteStream->new('<p>test</p>') %>
Newlines can be escaped with a backslash.
This is <%= 1 + 1 %> a\
single line
And a backslash in front of a newline 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 free indenting
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.
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.
$self->render(template => 'foo/bar');
Choosing a specific "format" and "handler" is just as easy.
$self->render(template => 'foo/bar', format => 'txt', handler => 'epl');
Because rendering a specific template is the most common task it also has a
shortcut.
$self->render('foo/bar');
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¶
Perl characters can be rendered with the "text" stash value, the given
content will be automatically encoded to bytes.
$self->render(text => 'Hello Woerld!');
Rendering data¶
Raw bytes can be rendered with the "data" stash value, no encoding
will be performed.
$self->render(data => $octets);
Rendering JSON¶
The "json" stash value allows you to pass Perl structures to the
renderer which get directly encoded to JSON.
$self->render(json => {foo => [1, 'test', 3]});
Partial rendering¶
Sometimes you might want to access the rendered result, for example to generate
emails, this can be done using the "partial" stash value.
my $html = $self->render('mail', partial => 1);
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.
$self->render(text => 'Hello.', format => 'txt');
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: text/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.
$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.
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;
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 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 $output;
Content blocks¶
Blocks and the helper "content_for" in
Mojolicious::Plugin::DefaultHelpers can also be used to pass whole sections of
the template to the layout.
@@ foo/bar.html.ep
% layout 'mylayout';
% content_for header => begin
<meta http-equiv="Content-Type" content="text/html">
% end
<div>Hello World!</div>
% content_for header => begin
<meta http-equiv="Pragma" content="no-cache">
% end
@@ layouts/mylayout.html.ep
<!DOCTYPE html>
<html>
<head><%= content_for 'header' %></head>
<body><%= content %></body>
</html>
Template inheritance¶
Inheritance takes the layout concept above one step further, the helpers
"content" in Mojolicious::Plugin::DefaultHelpers and
"extends" in Mojolicious::Plugin::DefaultHelpers allow you to build
a skeleton template with named blocks that child templates can override.
@@ first.html.ep
<!DOCTYPE html>
<html>
<head><title>Hello</title></head>
<body>
%= content header => begin
Default header
% end
<div>Hello World!</div>
%= content footer => begin
Default footer
% end
</body>
</html>
@@ second.html.ep
% extends 'first';
% content header => begin
New header
% end
This chain could go on and on to allow a very high level of template reuse.
Memorizing template blocks¶
Compiled templates are always cached in memory, but with the helper
"memorize" in Mojolicious::Plugin::DefaultHelpers you can go one
step further and prevent template blocks from getting executed more than once.
@@ cached.html.ep
% use Time::Piece;
%= memorize begin
This template was compiled at <%= localtime->hms %>.
% end
Adding helpers¶
Adding and redefining helpers is very easy, you can use them to do pretty much
everything.
use Mojolicious::Lite;
helper debug => sub {
my ($self, $string) = @_;
$self->app->log->debug($string);
};
get '/' => sub {
my $self = shift;
$self->debug('action');
} => 'index';
app->start;
__DATA__
@@ index.html.ep
% debug 'template';
Helpers can also accept template blocks as last argument, this for example
allows very pleasant to use tag helpers and filters.
use Mojolicious::Lite;
use Mojo::ByteStream;
helper trim_newline => sub {
my ($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, $string) = @_;
$self->app->log->debug($string);
});
}
1;
The "register" method will be called when you load the plugin.
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 relasing
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 @{$app->static->classes}, __PACKAGE__;
}
1;
__DATA__
@@ alertassets.js
alert("Hello World!");
@@ alertassets.html.ep
%= javascript "/alertassets.js"
Custom "exception" and "not_found"
templates¶
While the built-in "exception" and "not_found" templates are
very useful during development, you most likely want to show your users
something more related to your application in production. That's why
Mojolicious will always try to render "exception.$mode.$format.*" or
"not_found.$mode.$format.*" before falling back to the built-in
default templates.
@@ not_found.production.html.ep
<!DOCTYPE html>
<html>
<head><title>Page not found</title></head>
<body>Page does not seem to exist.</body>
</html>
ADVANCED¶
Less commonly used and more powerful features.
Internationalization¶
Thanks to Locale::Maketext all you need for basic internationalization support
in your application is the plugin Mojolicious::Plugin::I18N and a few lexicon
classes.
package MyApp::I18N::de;
use Mojo::Base -strict;
use base 'MyApp::I18N';
our %Lexicon = ('Hello World' => 'Hallo Welt');
package main;
use Mojolicious::Lite;
plugin I18N => {namespace => 'MyApp::I18N'};
get '/' => 'hello';
app->start;
__DATA__
@@ hello.html.ep
<%=l 'Hello World' %>!
Preferred languages will be automatically detected from the
"Accept-Language" header or can be manually changed with the helper
"languages" in Mojolicious::Plugin::I18N.
$ ./myapp.pl get -H 'Accept-Language: de' /
Chunked transfer encoding¶
For very dynamic content you might not know the response
"Content-Length" in advance, that's where the "chunked"
"Transfer-Encoding" comes 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.
# 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, so don't forget to use the utf8 pragma if necessary.
use Mojolicious::Lite;
use utf8;
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 "inflate" command
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 the
"ep_renderer" plugin with a custom configuration.
use Mojolicious::Lite;
plugin EPRenderer => {
name => 'mustache',
template => {
tag_start => '{{',
tag_end => '}}'
}
};
get '/' => 'index';
app->start;
__DATA__
@@ index.html.mustache
Hello {{= $name }}.
Mojo::Template contains the whole list of available options.
Adding your favorite template system¶
Maybe you would prefer a different template system than "ep", all you
have to do is add a new "handler".
use Mojolicious::Lite;
app->renderer->add_handler(
mine => sub {
my ($r, $c, $output, $options) = @_;
# One time use inline template
my $inline = $options->{inline};
# Generate relative template path
my $name = $r->template_name($options);
# Try to find appropriate template in DATA section
my $content = $r->get_data_template($options, $name);
# Generate absolute template path
my $path = $r->template_path($options);
# This part is up to you and your template system :)
...
# Pass the rendered result back to the renderer
$$output = 'The rendered result';
# Return true if rendering succeeded and false if it didn't
return 1;
}
);
get '/' => 'index';
app->start;
__DATA__
@@ index.html.mine
...
Since most template systems don't support templates in the "DATA"
section the renderer provides methods to help you with that.
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.