=encoding utf8 =head1 NAME Mojolicious::Guides::Rendering - Rendering =head1 OVERVIEW This document explains content generation with the L<Mojolicious> renderer. =head1 CONCEPTS Essentials every L<Mojolicious> developer should know. =head2 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 C<name.format.handler> scheme, with C<name> defaulting to C<controller/action> or the route name, C<format> defaulting to C<html> and C<handler> to C<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 C<templates> directories of the application or the C<DATA> section of the class C<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. =head2 Embedded Perl L<Mojolicious> includes a minimalistic but very powerful template system out of the box called Embedded Perl or C<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 C<E<lt>>, C<E<gt>>, C<&>, C<'> and C<"> in results from Perl expressions, which is the default to prevent XSS attacks against your application. <%= 'lalala' %> <%== '<p>test</p>' %> Only L<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) { %> <%= $foo =%> <% } %> Stash values that don't have invalid characters in their name get automatically initialized as normal variables in the template, and the controller object as C<$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'} %> =head1 BASICS Most commonly used features every L<Mojolicious> developer should know about. =head2 Automatic rendering The renderer can be manually started by calling the method L<Mojolicious::Controller/"render">, 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 L<Mojolicious/"controller_class">. =head2 Rendering templates The renderer will always try to detect the right template but you can also use the C<template> stash value to render a specific one. $self->render(template => 'foo/bar'); Choosing a specific C<format> and C<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'); =head2 Rendering inline templates Some renderers such as C<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 C<handler> too. $self->render(inline => "<%= shift->param('foo') %>", handler => 'epl'); =head2 Rendering text Perl characters can be rendered with the C<text> stash value, the given content will be automatically encoded to bytes. $self->render(text => 'Hello Wörld!'); =head2 Rendering data Raw bytes can be rendered with the C<data> stash value, no encoding will be performed. $self->render(data => $octets); =head2 Rendering JSON The C<json> stash value allows you to pass Perl data structures to the renderer which get directly encoded to JSON. $self->render(json => {foo => [1, 'test', 3]}); =head2 Partial rendering Sometimes you might want to access the rendered result, for example to generate emails, this can be done using the C<partial> stash value. my $html = $self->render('mail', partial => 1); =head2 Status code Response status codes can be changed with the C<status> stash value. $self->render(text => 'Oops.', status => 500); =head2 Content type The C<Content-Type> header of the response is actually based on the MIME type mapping of the C<format> stash value. $self->render(text => 'Hello.', format => 'txt'); These mappings can be easily extended or changed with L<Mojolicious/"types">. # 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; =head2 Stash data Any of the native Perl data types can be passed to templates through the L<Mojolicious::Controller/"stash">. $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 %>. % } =head2 Content negotiation For resources with different representations and that require truly C<RESTful> content negotiation you can also use L<Mojolicious::Controller/"respond_to"> instead of L<Mojolicious::Controller/"render">. # /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 C<Accept> request header, C<format> stash value or C<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 C<any> fallback will be used or an empty C<204> response rendered automatically. =head2 Rendering C<exception> and C<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. Especially during development they can be a great help, the methods L<Mojolicious::Controller/"render_exception"> and L<Mojolicious::Controller/"render_not_found"> can be used to render them manually. use Mojolicious::Lite; use Scalar::Util 'looks_like_number'; get '/divide/:dividend/by/:divisor' => sub { my $self = shift; my $dividend = $self->param('dividend'); my $divisor = $self->param('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 / $divisor); }; app->start; You can also change the templates of those pages, since you most likely want to show your users something more closely related to your application in production. The renderer will always try to find C<exception.$mode.$format.*> or C<not_found.$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><%= $exception %></body> </html> =head2 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 L<Mojolicious::Plugin::DefaultHelpers/"dumper"> for example will use L<Data::Dumper> to serialize whatever data structure you pass it, this can be very useful for debugging. We differentiate between C<default helpers> which are more general purpose like C<dumper> and C<tag helpers>, which are template specific and mostly used to generate C<HTML> tags. %= javascript '/script.js' %= javascript begin var a = 'b'; % end A list of all built-in helpers can be found in L<Mojolicious::Plugin::DefaultHelpers> and L<Mojolicious::Plugin::TagHelpers>. =head2 Layouts Most of the time when using C<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 L<Mojolicious::Plugin::DefaultHelpers/"layout"> and place the result of the current template with the helper L<Mojolicious::Plugin::DefaultHelpers/"content">. You can also pass along normal stash values to the C<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 C<layout> helper you could also just use the C<layout> stash value, or call L<Mojolicious::Controller/"render"> with the C<layout> argument. $self->render(template => 'mytemplate', layout => 'mylayout'); To set a C<layout> stash value application wide you can use L<Mojolicious/"defaults">. # Application package MyApp; use Mojo::Base 'Mojolicious'; sub startup { my $self = shift; # Default layout $self->defaults(layout => 'mylayout'); } 1; =head2 Including partial templates Like most helpers L<Mojolicious::Plugin::DefaultHelpers/"include"> 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 C<include> you could also just call L<Mojolicious::Controller/"render"> with the C<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 C<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> =head2 Reusable template blocks It's never fun to repeat yourself, that's why you can build reusable template blocks in C<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 C<begin> and C<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 $output; =head2 Content blocks Blocks and the helper L<Mojolicious::Plugin::DefaultHelpers/"content_for"> can also be used to pass whole sections of the template to the layout. @@ foo/bar.html.ep % layout 'mylayout'; % content_for header => begin <meta http-equiv="Content-Type" content="text/html"> % end <div>Hello World!</div> % content_for header => begin <meta http-equiv="Pragma" content="no-cache"> % end @@ layouts/mylayout.html.ep <!DOCTYPE html> <html> <head><%= content_for 'header' %></head> <body><%= content %></body> </html> =head2 Template inheritance Inheritance takes the layout concept above one step further, the helpers L<Mojolicious::Plugin::DefaultHelpers/"content"> and L<Mojolicious::Plugin::DefaultHelpers/"extends"> allow you to build a skeleton template with named blocks that child templates can override. @@ first.html.ep <!DOCTYPE html> <html> <head><title>Hello</title></head> <body> %= content header => begin Default header % end <div>Hello World!</div> %= content footer => begin Default footer % end </body> </html> @@ second.html.ep % extends 'first'; % content header => begin New header % end This chain could go on and on to allow a very high level of template reuse. =head2 Memorizing template blocks Compiled templates are always cached in memory, but with the helper L<Mojolicious::Plugin::DefaultHelpers/"memorize"> you can go one step further and prevent template blocks from getting executed more than once. @@ cached.html.ep % use Time::Piece; %= memorize begin This template was compiled at <%= localtime->hms %>. % end =head2 Adding helpers Adding and redefining helpers is very easy, you can use them to do pretty much everything. use Mojolicious::Lite; helper debug => sub { my ($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 L<Mojo::ByteStream> object can prevent accidental double escaping. =head2 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 C<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 C<CPAN> compatible plugin distribution can be automatically generated. $ mojo generate plugin DebugHelper And if you have a C<PAUSE> account (which can be requested at L<http://pause.perl.org>), you are only a few commands away from relasing it to C<CPAN>. $ perl Makefile.PL $ make test $ make manifest $ make dist $ mojo cpanify -u USER -p PASS Mojolicious-Plugin-DebugHelper-0.01.tar.gz =head2 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 C<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 C<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($base, 'public'); } 1; Both will work just like normal C<templates> and C<public> directories once you've installed and loaded the plugin, with slightly lower precedence. use Mojolicious::Lite; plugin 'AlertAssets'; get '/alert_me'; app->start; __DATA__ @@ alert_me.html.ep <!DOCTYPE html> <html> <head> <title>Alert me!</title> %= include 'alertassets' </head> <body>You've been alerted.</body> </html> And it works just the same for assets bundled in the C<DATA> section of your plugin. package Mojolicious::Plugin::AlertAssets; use Mojo::Base 'Mojolicious::Plugin'; sub register { my ($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" =head1 ADVANCED Less commonly used and more powerful features. =head2 Chunked transfer encoding For very dynamic content you might not know the response C<Content-Length> in advance, that's where the C<chunked> C<Transfer-Encoding> comes in handy. A common use would be to send the C<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 L<Mojolicious::Controller/"finish"> 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 (C<long polling>). Due to limitations in some web servers this might not work perfectly in all deployment environments. =head2 Encoding Templates stored in files are expected to be C<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 C<DATA> section are bound to the encoding of the Perl script, so don't forget to use the L<utf8> pragma if necessary. use Mojolicious::Lite; use utf8; get '/heart'; app->start; __DATA__ @@ heart.html.ep I ♥ Mojolicious! =head2 Base64 encoded DATA files Base64 encoded static files such as images can be easily stored in the C<DATA> section of your application, similar to templates. @@ favicon.ico (base64) ...base64 encoded image... =head2 Inflating DATA templates Templates stored in files get preferred over files from the C<DATA> section, this allows you to include a default set of templates in your application that the user can later customize. The C<inflate> command will write all templates and static files from the C<DATA> section into actual files in the C<templates> and C<public> directories. $ ./myapp.pl inflate =head2 Customizing the template syntax You can easily change the whole template syntax by loading L<Mojolicious::Plugin::EPRenderer> 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 {{= $name }}. L<Mojo::Template> contains the whole list of available options. =head2 Adding your favorite template system Maybe you would prefer a different template system than C<ep>, all you have to do is add a new C<handler>. use Mojolicious::Lite; app->renderer->add_handler( mine => sub { my ($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 C<DATA> section the renderer provides methods to help you with that. =head1 MORE You can continue with L<Mojolicious::Guides> now or take a look at the Mojolicious wiki L<http://github.com/kraih/mojo/wiki>, which contains a lot more documentation and examples by many different authors. =cut