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Introduction to Dancer! A Sinatra-inspired web framework for Perl! ! ! Mark Allen! mrallen1@yahoo.com! http://byte-me.org! https://github.com/mrallen1! https://bitbucket.org/mrallen1! https://metacpan.org/author/MALLEN!

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The Old Days!

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The Old Days cgi-lib.pl (1994-1998)! !

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The Old Days CGI.pm (1995-2011)! !

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The Old Days mod_perl (1996-2011)! !

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The Old Days Matt’s Script Archive (1995-2011)! ! Use instead:! http://nms-cgi.sourceforge.net/! (Thanks London.pm)! !

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The Old Days use CGI.pm;! ! my $q = CGI->new();! my ($a, $b, $c) = $q->param();! ! if ($a !~ /\d+/) {! !print $q->header(-status => ‘400 Bad request’);! !print “

Value of ‘a’ ($a) is not an integer

”;! !exit 0;! }! # yada, yada!

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The Old Days .htaccess Hack! ! ! RewriteEngine On! RewriteBase /abc! ! RewriteRule ^(.*)/(.*)/(.*)$ !abc.pl?a=$1;b=$2;c=$3! !

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The Old Days .htaccess Hack! ! # Use Web 2.0 style URLs, but keep CGI interface! RewriteEngine On! RewriteBase /abc! ! RewriteRule ^(.*)/(.*)/(.*)$ !abc.pl?a=$1;b=$2;c=$3! !

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The Old Days .htaccess Hack! ! # Use Web 2.0 style URLs, but keep CGI interface! RewriteEngine On! RewriteBase /abc! ! RewriteRule ^(.*)/(.*)/(.*)$ !abc.pl?a=$1;b=$2;c=$3! !

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The Old Days .htaccess Hack! ! # Use Web 2.0 style URLs, but keep CGI interface! RewriteEngine On! RewriteBase /abc! ! RewriteRule ^(.*)/(.*)/(.*)$ !abc.pl?a=$1;b=$2;c=$3! !

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The Old Days h"p://ﬂic.kr/p/5TWTR4

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The Old Days h"p://ﬂic.kr/p/5TWTR4

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Move over bacon, now there’s something leaner.! !

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Move over bacon Perl 5 Renaissance:! •  Moose! •  DBIx::Class! •  Plack! •  Tons of great new stuff in core perl 5.10+! !

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Move over bacon Do you ﬁnd Catalyst too ! heavyweight or intimidating?! !

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Move over bacon ! Me too!! ! !

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Move over bacon Enter Dancer! !

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Move over bacon Other Sinatra-inspired frameworks:! •  Mojo (Perl – TMTOWTDI)! •  Flask (Python)! •  Fitzgerald (PHP)! •  Express (Node.js)! !

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Move over bacon Dancer is:! •  Easy to learn! •  Expressive! •  Efﬁcient!

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Dancer is ...! ! Easy to learn!

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Easy to learn Basic Dancer concepts:! •  One (or more) HTTP verb(s)! •  A route! •  A handler!

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Easy to learn use Dancer;! ! get '/' => sub {! return 'Hello World!\n’;! };! ! start;!

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Easy to learn use Dancer;! ! get '/' => sub {! return 'Hello World!\n’;! };! ! start;!

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Easy to learn use Dancer;! ! get '/' => sub {! return 'Hello World!\n’;! };! ! start;!

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Easy to learn use Dancer;! ! get '/' => sub {! return 'Hello World!\n’;! };! ! start;!

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Easy to learn use Dancer;! ! get '/' => sub {! return 'Hello World!\n’;! };! ! start;!

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Easy to learn

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Easy to learn get '/' => sub {! my $db = connect_db();! my $sql = 'select id, title, text from entries order by id desc’;! my $sth = $db->prepare($sql) or die $db->errstr;! $sth->execute or die $sth->errstr;! template 'show_entries.tt', {! 'msg' => get_flash(),! 'add_entry_url' => uri_for('/add'),! 'entries' => $sth->fetchall_hashref('id'),! };! };!

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn show_entries.tt! !

<% entries.$id.title %>
! <% entries.$id.text %>! <% END %>! <% ELSE %>!
Unbelievable. No entries here so far! <% END %>!

!   !

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Easy to learn Directory structure  ! dancr/! ├── dancr.pl! ├── public! │ └── css! │ └── style.css! └── views! ├── layouts! │ └── main.tt! ├── login.tt! └── show_entries.tt!

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Dancer is...! ! Expressive!

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Expressive post '/add' => sub {! if ( not session('logged_in') ) {! return send_error("Not logged in", 401);! }! ! my $db = connect_db();! my $sql = 'insert into entries (title, text) values (?, ?)’;! my $sth = $db->prepare($sql)  or die $db->errstr;! $sth->execute(params->{'title'},   params->{'text'})   or die $sth->errstr;! ! set_flash('New entry posted!');! redirect '/’;! };!

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Expressive Little Bobby Tables! h"p://xkcd.com/327/

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Expressive post '/add' => sub {! if ( not session('logged_in') ) {! return send_error("Not logged in", 401);! }! # http://bobby-tables.com! my $db = connect_db();! my $sql = 'insert into entries (title, text) values (?, ?)’;! my $sth = $db->prepare($sql)  or die $db->errstr;! $sth->execute(params->{'title'},   params->{'text'})   or die $sth->errstr;! ! set_flash('New entry posted!');! redirect '/’;! };!

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Expressive

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Expressive Conﬁguration  ! •  Session Engine! •  Template Engine! •  Logging ! •  Plugins!

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Expressive Conﬁguration Examples!     set 'session' => 'Simple';  set 'template' =>'template_toolkit';  set 'logger' => 'console';  set 'log' => 'debug';  set 'show_errors' => 1;  !

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Expressive Conﬁguration Examples!     set 'session' => 'Simple';  set 'template' =>'template_toolkit';  set 'logger' => 'console';  set 'log' => 'debug';  set 'show_errors' => 1;  !

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Expressive Conﬁguration    Use any non-reserved key/value pair.    set 'username' => 'admin';  set 'password' => 'password';! !

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Expressive Routes with regex! !   get qr{\A\/(?

[A-Za-z0-9]+)\Z} => sub {!
my $decode = decode_base36( 
uc captures->{'code'}!
);!
...;!
};!

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Expressive Routes with regex! !   get qr{\A\/(?

[A-Za-z0-9]+)\Z} => sub {!
my $decode = decode_base36( 
uc captures->{'code'}!
);!
...;!
};!

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Expressive Routes with regex! ! use v5.10;  get qr{\A\/(?

[A-Za-z0-9]+)\Z} => sub {!
my $decode = decode_base36( 
uc captures->{'code'}!
);!
...;!
};!

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Expressive Routes with regex! ! use v5.10;  get qr{\A\/(?

[A-Za-z0-9]+)\Z} => sub {!
my $decode = decode_base36( 
uc captures->{'code'}!
);!
...;!
};!

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Expressive Routes with named params! ! get '/:code/stats' => sub {! my $decode = decode_base36(  uc params->{'code'}  );! ...;! };!

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Expressive Routes with named params! ! get '/:code/stats' => sub {! my $decode = decode_base36(  uc params->{'code'}  );! ...;! };!

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Expressive Routes with named params! ! get qr{^/(.+)/stats$} => sub {  params(‘code’) = $1;  # input sanity goes here  ...;  };!

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Expressive use CGI.pm;! ! my $q = CGI->new();! my ($a, $b, $c) = $q->param();! ! if ($a !~ /\d+/) {! !print $q->header(-status => ‘400 Bad request’);! !print “

Value of ‘a’ ($a) is not an integer

”;! !exit 0;! }! # yada, yada!

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Expressive ! ! ! ! use v5.10;  use Dancer;    ! get qr{/(?\d+)/(?.+)/(?.+)} => sub {! # Route will only match if a is an integer!  # No more sanitation/validation necessary  ...;  };! !

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Dancer is...    ! Efﬁcient!

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Efficient any ['get', 'post'] => '/login' => sub {! my $err;! if ( request->is_post ) {! if ( params->{'username'} ne setting('username') ) {! $err = "Invalid username”;! }! elsif ( params->{'password'} ne setting('password') ) {! $err = "Invalid password”;! }! else {! session 'logged_in' => true;! set_flash('You are logged in.');! redirect '/’;! }! }! template 'login.tt', {! 'err' => $err,! };! };!

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Efficient Hook Before / After! •  De/Serialization! •  Rendering! •  Template! •  Errors!

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Efficient Forward! ! get '/demo/foo/:bar' => sub {! my $bar = param->{'bar'};! # magically use demo DB! ...;! return forward "/foo/$bar";! };! !

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Efficient Preﬁx! ! prefix '/user'; # begins scope! ! get '/view/:id' => sub { ...; };! post '/add' => sub { ...; };! any ['get', 'post'] => '/edit/:id' => sub { ...; };! ! prefix undef; # ends scope! ! get '/view/:id' => sub { ...; };!

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Efficient Dancer Plugins add keywords  ! •  Auto-create RSS feeds! •  Integrate Twitter for authN! •  DBIx::Class! •  DWIM CRUD apps! •  ...and more!

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Efficient Dancer::Plugin::Database  ! database keyword gets $dbh! ! my $sth = database->prepare("SELECT * FROM mytable WHERE id = ?");! $sth->execute(42);! template 'userdetail.tt', {! row => $sth->fetchrow_hashref()! };!

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Efficient Sweet, sweet syntactic sugar:! ! ! database->quick_insert('mytable', \%data);! template 'userdetail.tt', {! row => database->quick_select('mytable', { id => 42 })! };! !

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Dancer is...! ! Awesome! !

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Awesome Source code:! { hg | git } clone https://bitbucket.org/mrallen1/dancr! ! See also:! https://metacpan.org/module/Dancer! https://metacpan.org/module/Dancer::Plugin::Database  ! Install:! curl -L http://cpanmin.us | perl - Dancer YAML Template! !

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Awesome Thank You!! !

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Value of ‘a’ ($a) is not an integer

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<% entries.$id.title %>

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