Mojolicious::Guides::RUserrContributed Perl DMojolicious::Guides::Rendering(3)NAMEMojolicious::Guides::Rendering - Rendering
OVERVIEW
Generating content 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" directory of the application
or the "DATA" section of the class "main".
__DATA__
@@ time.html.ep
<!doctype html><html>
<head><title>Time</title></head>
<body><%= localtime time %></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>
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>') %>
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 instance 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 "render" controller
method, but that's usually not necessary, because it will get
automatically called if nothing has been rendered after the routes
dispatcher 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 "render" manually you
can make sure that templates use the current controller instance and
not the default controller specified in the "controller_class"
attribute of the application class.
Rendering Templates ("template")
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');
All values passed to the "render" call are only temporarily assigned to
the stash and get reset again once rendering is finished.
Rendering Inline Templates ("inline")
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 ("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 ("data")
Raw bytes can be rendered with the "data" stash value, no encoding will
be performed.
$self->render(data => $octets);
Rendering JSON ("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 ("partial")
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 ("status")
Response status codes can be changed with the "status" stash value.
$self->render(text => 'Oops!', status => 500);
Content Type ("format")
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
Data can be passed to templates through the "stash" in any of the
native Perl data types.
$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" instead of
"render".
# "Accept: application/json" -> "json"
# "Accept: text/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.
# "Accept: application/json" -> "json"
# "Accept: text/html" -> "html"
# "Accept: image/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 "dumper" helper 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 "layout" helper and
place the result of the current template with the "content" helper.
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" with the "layout" argument.
$self->render(template => 'mytemplate', layout => 'mylayout');
To set a "layout" stash value application wide you can use "defaults".
# 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 the "include" helper 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" 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.
<% my $block = begin %>
<% my $name = shift; %>
Hello <%= $name %>.
<% end %>
<%= $block->('Sebastian') %>
<%= $block->('Sara') %>
Blocks are always delimited by the "begin" and "end" keywords.
% my $block = begin
% my $name = shift;
Hello <%= $name %>.
% end
% for (1 .. 10) {
%= $block->('Sebastian')
% }
A naive translation to equivalent Perl code could look like this.
my $output = '';
my $block = sub {
my $name = shift;
my $output = '';
$output .= "Hello $name.";
return $output;
}
for (1 .. 10) {
$output .= $block->('Sebastian');
}
print $output;
Content Blocks
Blocks and the "content_for" helper can also be used to pass whole
sections of the template to the layout.
@@ foo/bar.html.ep
% layout 'mylayout';
<% content_for header => begin %>
<title>MyApp!</title>
<% end %>
Hello World!
<% content_for header => begin %>
<meta http-equiv="Pragma" content="no-cache">
<% end %>
@@ layouts/mylayout.html.ep
<!doctype html><html>
<head><%= content_for 'header' %></head>
<body><%= content %></body>
</html>
Template Inheritance
Inheritance takes the layout concept above one step further. Unlike
"content_for" the "content" helper does not allow appending to existing
values, this makes it possible to overload whole template sections.
The only difference between "layout" and "extends" is that extended
templates don't get prefixed with "layouts/".
@@ first.html.ep
%# "<div>First header!First footer!</div>"
<div>
<%= content header => begin %>
First header!
<% end %>
<%= content footer => begin %>
First footer!
<% end %>
</div>
@@ second.html.ep
%# "<div>Second header!First footer!</div>"
% extends 'first';
<% content header => begin %>
Second header!
<% end %>
@@ third.html.ep
%# "<div>Second header!Third footer!</div>"
% extends 'second';
<% content footer => begin %>
Third footer!
<% end %>
This chain could go on and on to allow a very high level of template
reuse.
Memorizing Template Blocks
Compiled templates are always cached in memory, but with the "memorize"
helper you can go one step further and prevent template blocks from
being executed more than once.
<%= memorize begin %>
This template was compiled at <%= localtime time %>.
<% end %>
Adding Helpers
Adding and redefining helpers is very easy, you can use them to do
pretty much everything.
use Mojolicious::Lite;
helper debug => sub {
my ($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
Mode Specific "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.
@@ exception.production.html.ep
<!doctype html><html>
<head><title>Server Error</title></head>
<body>Something bad happened!</body>
</html>
@@ 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.
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>');
$self->write_chunk('<link href="example.css" rel="stylesheet"');
$self->write_chunk(' type="text/css"></head>', sub {
my $self = shift;
$self->write_chunk('<body>Example</body></html>');
$self->write_chunk('');
});
The optional drain callback ensures that all previous chunks have been
written before processing continues. An empty chunk marks the end of
the stream.
22
<html><head><title>Example</title>
29
<link href="example.css" rel="stylesheet"
17
type="text/css"></head>
1C
<body>Example</body></html>
0
Especially in combination with long connection 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!';
}
);
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.
perl v5.14.1 2011-09-10 Mojolicious::Guides::Rendering(3)
