Provided by: libcatalyst-manual-perl_5.9011-2_all 
NAME
Catalyst::Manual::Cookbook - Cooking with Catalyst
DESCRIPTION
Yummy code like your mum used to bake!
RECIPES
Basics
These recipes cover some basic stuff that is worth knowing for Catalyst developers.
Delivering a Custom Error Page
By default, Catalyst will display its own error page whenever it encounters an error in
your application. When running under "-Debug" mode, the error page is a useful screen
including the error message and Data::Dump output of the relevant parts of the $c context
object. When not in "-Debug", users see a simple "Please come back later" screen.
To use a custom error page, use a special "end" method to short-circuit the error
processing. The following is an example; you might want to adjust it further depending on
the needs of your application (for example, any calls to "fillform" will probably need to
go into this "end" method; see Catalyst::Plugin::FillInForm).
sub end : Private {
my ( $self, $c ) = @_;
if ( scalar @{ $c->error } ) {
$c->stash->{errors} = $c->error;
for my $error ( @{ $c->error } ) {
$c->log->error($error);
}
$c->stash->{template} = 'errors.tt';
$c->forward('MyApp::View::TT');
$c->clear_errors;
}
return 1 if $c->response->status =~ /^3\d\d$/;
return 1 if $c->response->body;
unless ( $c->response->content_type ) {
$c->response->content_type('text/html; charset=utf-8');
}
$c->forward('MyApp::View::TT');
}
You can manually set errors in your code to trigger this page by calling
$c->error( 'You broke me!' );
Disable statistics
Just add this line to your application class if you don't want those nifty statistics in
your debug messages.
sub Catalyst::Log::info { }
Enable debug status in the environment
Normally you enable the debugging info by adding the "-Debug" flag to your "use Catalyst"
statement . However, you can also enable it using environment variable, so you can (for
example) get debug info without modifying your application scripts. Just set
"CATALYST_DEBUG" or "<MYAPP>_DEBUG" to a true value.
Sessions
When you have your users identified, you will want to somehow remember that fact, to save
them from having to identify themselves for every single page. One way to do this is to
send the username and password parameters in every single page, but that's ugly, and won't
work for static pages.
Sessions are a method of saving data related to some transaction, and giving the whole
collection a single ID. This ID is then given to the user to return to us on every page
they visit while logged in. The usual way to do this is using a browser cookie.
Catalyst uses two types of plugins to represent sessions:
State
A State module is used to keep track of the state of the session between the users
browser, and your application.
A common example is the Cookie state module, which sends the browser a cookie containing
the session ID. It will use default value for the cookie name and domain, so will "just
work" when used.
Store
A Store module is used to hold all the data relating to your session, for example the
users ID, or the items for their shopping cart. You can store data in memory (FastMmap),
in a file (File) or in a database (DBI).
Authentication magic
If you have included the session modules in your application, the Authentication modules
will automagically use your session to save and retrieve the user data for you.
Using a session
Once the session modules are loaded, the session is available as "$c->session", and can be
written to and read from as a simple hash reference.
EXAMPLE
package MyApp;
use Moose;
use namespace::autoclean;
use Catalyst qw/
Session
Session::Store::FastMmap
Session::State::Cookie
/;
extends 'Catalyst';
__PACKAGE__->setup;
package MyApp::Controller::Foo;
use Moose;
use namespace::autoclean;
BEGIN { extends 'Catalyst::Controller' };
## Write data into the session
sub add_item : Local {
my ( $self, $c ) = @_;
my $item_id = $c->req->params->{item};
push @{ $c->session->{items} }, $item_id;
}
## A page later we retrieve the data from the session:
sub get_items : Local {
my ( $self, $c ) = @_;
$c->stash->{items_to_display} = $c->session->{items};
}
More information
Catalyst::Plugin::Session
Catalyst::Plugin::Session::State::Cookie
Catalyst::Plugin::Session::State::URI
Catalyst::Plugin::Session::Store::FastMmap
Catalyst::Plugin::Session::Store::File
Catalyst::Plugin::Session::Store::DBI
Configure your application
You configure your application with the "config" method in your application class. This
can be hard-coded, or brought in from a separate configuration file.
Using Config::General
Config::General is a method for creating flexible and readable configuration files. It's a
great way to keep your Catalyst application configuration in one easy-to-understand
location.
Now create myapp.conf in your application home:
name MyApp
# session; perldoc Catalyst::Plugin::Session::FastMmap
<Session>
expires 3600
rewrite 0
storage /tmp/myapp.session
</Session>
# emails; perldoc Catalyst::Plugin::Email
# this passes options as an array :(
Mail SMTP
Mail localhost
This is equivalent to:
# configure base package
__PACKAGE__->config( name => MyApp );
# configure authentication
__PACKAGE__->config(
'Plugin::Authentication' => {
user_class => 'MyApp::Model::MyDB::Customer',
...
},
_;
# configure sessions
__PACKAGE__->config(
session => {
expires => 3600,
...
},
);
# configure email sending
__PACKAGE__->config( email => [qw/SMTP localhost/] );
Catalyst explains precedence of multiple sources for configuration values, how to access
the values in your components, and many 'base' config variables used internally.
See also Config::General.
Skipping your VCS's directories
Catalyst uses Module::Pluggable to load Models, Views, and Controllers. Module::Pluggable
will scan through all directories and load modules it finds. Sometimes you might want to
skip some of these directories, for example when your version control system makes a
subdirectory with meta-information in every version-controlled directory. While Catalyst
skips subversion and CVS directories already, there are other source control systems.
Here is the configuration you need to add their directories to the list to skip.
You can make Catalyst skip these directories using the Catalyst config:
# Configure the application
__PACKAGE__->config(
name => 'MyApp',
setup_components => { except => qr/SCCS/ },
);
See the Module::Pluggable manual page for more information on except and other options.
Users and Access Control
Most multiuser, and some single-user web applications require that users identify
themselves, and the application is often required to define those roles. The recipes
below describe some ways of doing this.
Authentication (logging in)
This is extensively covered in other documentation; see in particular
Catalyst::Plugin::Authentication and the Authentication chapter of the Tutorial at
Catalyst::Manual::Tutorial::06_Authorization.
Pass-through login (and other actions)
An easy way of having assorted actions that occur during the processing of a request that
are orthogonal to its actual purpose - logins, silent commands etc. Provide actions for
these, but when they're required for something else fill e.g. a form variable __login and
have a sub begin like so:
sub begin : Private {
my ($self, $c) = @_;
foreach my $action (qw/login docommand foo bar whatever/) {
if ($c->req->params->{"__${action}"}) {
$c->forward($action);
}
}
}
Authentication/Authorization
This is done in several steps:
Verification
Getting the user to identify themselves, by giving you some piece of information known
only to you and the user. Then you can assume that the user is who they say they are.
This is called credential verification.
Authorization
Making sure the user only accesses functions you want them to access. This is done by
checking the verified user's data against your internal list of groups, or allowed
persons for the current page.
Modules
The Catalyst Authentication system is made up of many interacting modules, to give you the
most flexibility possible.
Credential verifiers
A Credential module tables the user input, and passes it to a Store, or some other system,
for verification. Typically, a user object is created by either this module or the Store
and made accessible by a "$c->user" call.
Examples:
Password - Simple username/password checking.
HTTPD - Checks using basic HTTP auth.
TypeKey - Check using the typekey system.
Storage backends
A Storage backend contains the actual data representing the users. It is queried by the
credential verifiers. Updating the store is not done within this system; you will need to
do it yourself.
Examples:
DBIC - Storage using a database via DBIx::Class.
Minimal - Storage using a simple hash (for testing).
User objects
A User object is created by either the storage backend or the credential verifier, and is
filled with the retrieved user information.
Examples:
Hash - A simple hash of keys and values.
ACL authorization
ACL stands for Access Control List. The ACL plugin allows you to regulate access on a
path-by-path basis, by listing which users, or roles, have access to which paths.
Roles authorization
Authorization by roles is for assigning users to groups, which can then be assigned to
ACLs, or just checked when needed.
Logging in
When you have chosen your modules, all you need to do is call the "$c->authenticate"
method. If called with no parameters, it will try to find suitable parameters, such as
username and password, or you can pass it these values.
Checking roles
Role checking is done by using the "$c->check_user_roles" method. This will check using
the currently logged-in user (via "$c->user"). You pass it the name of a role to check,
and it returns true if the user is a member.
EXAMPLE
package MyApp;
use Moose;
use namespace::autoclean;
extends qw/Catalyst/;
use Catalyst qw/
Authentication
Authorization::Roles
/;
__PACKAGE__->config(
authentication => {
default_realm => 'test',
realms => {
test => {
credential => {
class => 'Password',
password_field => 'password',
password_type => 'self_check',
},
store => {
class => 'Htpasswd',
file => 'htpasswd',
},
},
},
},
);
package MyApp::Controller::Root;
use Moose;
use namespace::autoclean;
BEGIN { extends 'Catalyst::Controller' }
__PACKAGE__->config(namespace => '');
sub login : Local {
my ($self, $c) = @_;
if ( my $user = $c->req->params->{user}
and my $password = $c->req->param->{password} )
{
if ( $c->authenticate( username => $user, password => $password ) ) {
$c->res->body( "hello " . $c->user->name );
} else {
# login incorrect
}
}
else {
# invalid form input
}
}
sub restricted : Local {
my ( $self, $c ) = @_;
$c->detach("unauthorized")
unless $c->check_user_roles( "admin" );
# do something restricted here
}
Using authentication in a testing environment
Ideally, to write tests for authentication/authorization code one would first set up a
test database with known data, then use Test::WWW::Mechanize::Catalyst to simulate a user
logging in. Unfortunately this can be rather awkward, which is why it's a good thing that
the authentication framework is so flexible.
Instead of using a test database, one can simply change the authentication store to
something a bit easier to deal with in a testing environment. Additionally, this has the
advantage of not modifying one's database, which can be problematic if one forgets to use
the testing instead of production database.
Alternatively, if you want to authenticate real users, but not have to worry about their
passwords, you can use Catalyst::Authentication::Credential::Testing to force all users to
authenticate with a global password.
More information
Catalyst::Plugin::Authentication has a longer explanation.
Authorization
Introduction
Authorization is the step that comes after authentication. Authentication establishes that
the user agent is really representing the user we think it's representing, and then
authorization determines what this user is allowed to do.
Role Based Access Control
Under role based access control each user is allowed to perform any number of roles. For
example, at a zoo no one but specially trained personnel can enter the moose cage (Mynd
you, møøse bites kan be pretty nasti!). For example:
package Zoo::Controller::MooseCage;
sub feed_moose : Local {
my ( $self, $c ) = @_;
$c->model( "Moose" )->eat( $c->req->params->{food} );
}
With this action, anyone can just come into the moose cage and feed the moose, which is a
very dangerous thing. We need to restrict this action, so that only a qualified moose
feeder can perform that action.
The Authorization::Roles plugin lets us perform role based access control checks. Let's
load it:
use parent qw/Catalyst/;
use Catalyst qw/
Authentication
Authorization::Roles
/;
And now our action should look like this:
sub feed_moose : Local {
my ( $self, $c ) = @_;
if ( $c->check_roles( "moose_feeder" ) ) {
$c->model( "Moose" )->eat( $c->req->params->{food} );
} else {
$c->stash->{error} = "unauthorized";
}
}
This checks "$c->user", and only if the user has all the roles in the list, a true value
is returned.
"check_roles" has a sister method, "assert_roles", which throws an exception if any roles
are missing.
Some roles that might actually make sense in, say, a forum application:
• administrator
• moderator
each with a distinct task (system administration versus content administration).
Access Control Lists
Checking for roles all the time can be tedious and error prone.
The Authorization::ACL plugin lets us declare where we'd like checks to be done
automatically for us.
For example, we may want to completely block out anyone who isn't a "moose_feeder" from
the entire "MooseCage" controller:
Zoo->deny_access_unless( "/moose_cage", [qw/moose_feeder/] );
The role list behaves in the same way as "check_roles". However, the ACL plugin isn't
limited to just interacting with the Roles plugin. We can use a code reference instead.
For example, to allow either moose trainers or moose feeders into the moose cage, we can
create a more complex check:
Zoo->deny_access_unless( "/moose_cage", sub {
my $c = shift;
$c->check_roles( "moose_trainer" ) || $c->check_roles( "moose_feeder" );
});
The more specific a role, the earlier it will be checked. Let's say moose feeders are now
restricted to only the "feed_moose" action, while moose trainers get access everywhere:
Zoo->deny_access_unless( "/moose_cage", [qw/moose_trainer/] );
Zoo->allow_access_if( "/moose_cage/feed_moose", [qw/moose_feeder/]);
When the "feed_moose" action is accessed the second check will be made. If the user is a
"moose_feeder", then access will be immediately granted. Otherwise, the next rule in line
will be tested - the one checking for a "moose_trainer". If this rule is not satisfied,
access will be immediately denied.
Rules applied to the same path will be checked in the order they were added.
Lastly, handling access denial events is done by creating an "access_denied" private
action:
sub access_denied : Private {
my ( $self, $c, $action ) = @_;
}
This action works much like auto, in that it is inherited across namespaces (not like
object oriented code). This means that the "access_denied" action which is nearest to the
action which was blocked will be triggered.
If this action does not exist, an error will be thrown, which you can clean up in your
"end" private action instead.
Also, it's important to note that if you restrict access to "/" then "end", "default",
etc. will also be restricted.
MyApp->acl_allow_root_internals;
will create rules that permit access to "end", "begin", and "auto" in the root of your app
(but not in any other controller).
Models
Models are where application data belongs. Catalyst is extremely flexible with the kind
of models that it can use. The recipes here are just the start.
Using existing DBIC (etc.) classes with Catalyst
Many people have existing Model classes that they would like to use with Catalyst (or,
conversely, they want to write Catalyst models that can be used outside of Catalyst, e.g.
in a cron job). It's trivial to write a simple component in Catalyst that slurps in an
outside Model:
package MyApp::Model::DB;
use base qw/Catalyst::Model::DBIC::Schema/;
__PACKAGE__->config(
schema_class => 'Some::DBIC::Schema',
connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}],
);
1;
and that's it! Now "Some::DBIC::Schema" is part of your Cat app as "MyApp::Model::DB".
DBIx::Class as a Catalyst Model
See Catalyst::Model::DBIC::Schema.
Create accessors to preload static data once per server instance
When you have data that you want to load just once from the model at startup, instead of
for each request, use mk_group_accessors to create accessors and tie them to resultsets in
your package that inherits from DBIx::Class::Schema:
package My::Schema;
use base qw/DBIx::Class::Schema/;
__PACKAGE__->register_class('RESULTSOURCEMONIKER',
'My::Schema::RESULTSOURCE');
__PACKAGE__->mk_group_accessors('simple' =>
qw(ACCESSORNAME1 ACCESSORNAME2 ACCESSORNAMEn));
sub connection {
my ($self, @rest) = @_;
$self->next::method(@rest);
# $self is now a live My::Schema object, complete with DB connection
$self->ACCESSORNAME1([ $self->resultset('RESULTSOURCEMONIKER')->all ]);
$self->ACCESSORNAME2([ $self->resultset('RESULTSOURCEMONIKER')->search({ COLUMN => { '<' => '30' } })->all ]);
$self->ACCESSORNAMEn([ $self->resultset('RESULTSOURCEMONIKER')->find(1) ]);
}
1;
and now in the controller, you can now access any of these without a per-request fetch:
$c->stash->{something} = $c->model('My::Schema')->schema->ACCESSORNAME;
XMLRPC
Unlike SOAP, XMLRPC is a very simple (and elegant) web-services protocol, exchanging small
XML messages like these:
Request:
POST /api HTTP/1.1
TE: deflate,gzip;q=0.3
Connection: TE, close
Accept: text/xml
Accept: multipart/*
Host: 127.0.0.1:3000
User-Agent: SOAP::Lite/Perl/0.60
Content-Length: 192
Content-Type: text/xml
<?xml version="1.0" encoding="UTF-8"?>
<methodCall>
<methodName>add</methodName>
<params>
<param><value><int>1</int></value></param>
<param><value><int>2</int></value></param>
</params>
</methodCall>
Response:
Connection: close
Date: Tue, 20 Dec 2005 07:45:55 GMT
Content-Length: 133
Content-Type: text/xml
Status: 200
X-Catalyst: 5.70
<?xml version="1.0" encoding="us-ascii"?>
<methodResponse>
<params>
<param><value><int>3</int></value></param>
</params>
</methodResponse>
Now follow these few steps to implement the application:
1. Install Catalyst (5.61 or later), Catalyst::Plugin::XMLRPC (0.06 or later) and
SOAP::Lite (for XMLRPCsh.pl).
2. Create an application framework:
% catalyst.pl MyApp
...
% cd MyApp
3. Add the XMLRPC plugin to MyApp.pm
use Catalyst qw/-Debug Static::Simple XMLRPC/;
4. Add an API controller
% ./script/myapp_create.pl controller API
5. Add a XMLRPC redispatch method and an add method with Remote attribute to
lib/MyApp/Controller/API.pm
sub default :Path {
my ( $self, $c ) = @_;
$c->xmlrpc;
}
sub add : Remote {
my ( $self, $c, $a, $b ) = @_;
return $a + $b;
}
The default action is the entry point for each XMLRPC request. It will redispatch
every request to methods with Remote attribute in the same class.
The "add" method is not a traditional action; it has no private or public path. Only
the XMLRPC dispatcher knows it exists.
6. That's it! You have built your first web service. Let's test it with XMLRPCsh.pl (part
of SOAP::Lite):
% ./script/myapp_server.pl
...
% XMLRPCsh.pl http://127.0.0.1:3000/api
Usage: method[(parameters)]
> add( 1, 2 )
--- XMLRPC RESULT ---
'3'
Tip
Your return data type is usually auto-detected, but you can easily enforce a specific one.
sub add : Remote {
my ( $self, $c, $a, $b ) = @_;
return RPC::XML::int->new( $a + $b );
}
Views
Views pertain to the display of your application. As with models, Catalyst is uncommonly
flexible. The recipes below are just a start.
Catalyst::View::TT
One of the first things you probably want to do when starting a new Catalyst application
is set up your View. Catalyst doesn't care how you display your data; you can choose to
generate HTML, PDF files, or plain text if you wanted.
Most Catalyst applications use a template system to generate their HTML, and though there
are several template systems available, Template Toolkit is probably the most popular.
Once again, the Catalyst developers have done all the hard work, and made things easy for
the rest of us. Catalyst::View::TT provides the interface to Template Toolkit, and
provides Helpers which let us set it up that much more easily.
Creating your View
Catalyst::View::TT provides two different helpers for us to use: TT and TTSite.
TT
Create a basic Template Toolkit View using the provided helper script:
script/myapp_create.pl view TT TT
This will create lib/MyApp/View/MyView.pm, which is going to be pretty empty to start.
However, it sets everything up that you need to get started. You can now define which
template you want and forward to your view. For instance:
sub hello : Local {
my ( $self, $c ) = @_;
$c->stash->{template} = 'hello.tt';
$c->forward( $c->view('TT') );
}
In practice you wouldn't do the forwarding manually, but would use
Catalyst::Action::RenderView.
TTSite
Although the TT helper does create a functional, working view, you may find yourself
having to create the same template files and changing the same options every time you
create a new application. The TTSite helper saves us even more time by creating the basic
templates and setting some common options for us.
Once again, you can use the helper script:
script/myapp_create.pl view TT TTSite
This time, the helper sets several options for us in the generated View.
__PACKAGE__->config({
CATALYST_VAR => 'Catalyst',
INCLUDE_PATH => [
MyApp->path_to( 'root', 'src' ),
MyApp->path_to( 'root', 'lib' )
],
PRE_PROCESS => 'config/main',
WRAPPER => 'site/wrapper',
ERROR => 'error.tt2',
TIMER => 0
});
• "INCLUDE_PATH" defines the directories that Template Toolkit should search for the
template files.
• "PRE_PROCESS" is used to process configuration options which are common to every
template file.
• "WRAPPER" is a file which is processed with each template, usually used to easily
provide a common header and footer for every page.
In addition to setting these options, the TTSite helper also created the template and
config files for us! In the 'root' directory, you'll notice two new directories: src and
lib.
Several configuration files in root/lib/config are called by "PRE_PROCESS".
The files in root/lib/site are the site-wide templates, called by "WRAPPER", and display
the html framework, control the layout, and provide the templates for the header and
footer of your page. Using the template organization provided makes it much easier to
standardize pages and make changes when they are (inevitably) needed.
The template files that you will create for your application will go into root/src, and
you don't need to worry about putting the "<html>" or "<head>" sections; just put in the
content. The "WRAPPER" will the rest of the page around your template for you.
"$c->stash"
Of course, having the template system include the header and footer for you isn't all that
we want our templates to do. We need to be able to put data into our templates, and have
it appear where and how we want it, right? That's where the stash comes in.
In our controllers, we can add data to the stash, and then access it from the template.
For instance:
sub hello : Local {
my ( $self, $c ) = @_;
$c->stash->{name} = 'Adam';
$c->stash->{template} = 'hello.tt';
$c->forward( $c->view('TT') );
}
Then, in hello.tt:
<strong>Hello, [% name %]!</strong>
When you view this page, it will display "Hello, Adam!"
All of the information in your stash is available, by its name/key, in your templates. And
your data don't have to be plain, old, boring scalars. You can pass array references and
hash references, too.
In your controller:
sub hello : Local {
my ( $self, $c ) = @_;
$c->stash->{names} = [ 'Adam', 'Dave', 'John' ];
$c->stash->{template} = 'hello.tt';
$c->forward( $c->view('TT') );
}
In hello.tt:
[% FOREACH name IN names %]
<strong>Hello, [% name %]!</strong><br />
[% END %]
This allowed us to loop through each item in the arrayref, and display a line for each
name that we have.
This is the most basic usage, but Template Toolkit is quite powerful, and allows you to
truly keep your presentation logic separate from the rest of your application.
"$c->uri_for()"
One of my favorite things about Catalyst is the ability to move an application around
without having to worry that everything is going to break. One of the areas that used to
be a problem was with the http links in your template files. For example, suppose you have
an application installed at "http://www.domain.com/Calendar". The links point to
""/Calendar"", ""/Calendar/2005"", ""/Calendar/2005/10"", etc. If you move the
application to be at "http://www.mydomain.com/Tools/Calendar", then all of those links
will suddenly break.
That's where "$c->uri_for()" comes in. This function will merge its parameters with either
the base location for the app, or its current namespace. Let's take a look at a couple of
examples.
In your template, you can use the following:
<a href="[% c.uri_for('/login') %]">Login Here</a>
Although the parameter starts with a forward slash, this is relative to the application
root, not the webserver root. This is important to remember. So, if your application is
installed at "http://www.domain.com/Calendar", then the link would be
"http://www.mydomain.com/Calendar/Login". If you move your application to a different
domain or path, then that link will still be correct.
Likewise,
<a href="[% c.uri_for('2005','10', '24') %]">October, 24 2005</a>
The first parameter does NOT have a forward slash, and so it will be relative to the
current namespace. If the application is installed at "http://www.domain.com/Calendar".
and if the template is called from "MyApp::Controller::Display", then the link would
become "http://www.domain.com/Calendar/Display/2005/10/24".
If you want to link to a parent uri of your current namespace you can prefix the arguments
with multiple '"../"':
<a href="[% c.uri_for('../../view', stashed_object.id) %]">User view</a>
Once again, this allows you to move your application around without having to worry about
broken links. But there's something else, as well. Since the links are generated by
"uri_for", you can use the same template file by several different controllers, and each
controller will get the links that its supposed to. Since we believe in Don't Repeat
Yourself, this is particularly helpful if you have common elements in your site that you
want to keep in one file.
Further Reading:
Catalyst
Catalyst::View::TT
Template
Adding RSS feeds
Adding RSS feeds to your Catalyst applications is simple. We'll see two different
approaches here, but the basic premise is that you forward to the normal view action first
to get the objects, then handle the output differently.
Using XML::Feed
Assuming we have a "view" action that populates 'entries' with some DBIx::Class iterator,
the code would look something like this:
sub rss : Local {
my ($self,$c) = @_;
$c->forward('view'); # get the entries
my $feed = XML::Feed->new('RSS');
$feed->title( $c->config->{name} . ' RSS Feed' );
$feed->link( $c->req->base ); # link to the site.
$feed->description('Catalyst advent calendar'); Some description
# Process the entries
while( my $entry = $c->stash->{entries}->next ) {
my $feed_entry = XML::Feed::Entry->new('RSS');
$feed_entry->title($entry->title);
$feed_entry->link( $c->uri_for($entry->link) );
$feed_entry->issued( DateTime->from_epoch(epoch => $entry->created) );
$feed->add_entry($feed_entry);
}
$c->res->body( $feed->as_xml );
}
With this approach you're pretty sure to get something that validates.
Note that for both of the above approaches, you'll need to set the content type like this:
$c->res->content_type('application/rss+xml');
Final words
You could generalize the second variant easily by replacing 'RSS' with a variable, so you
can generate Atom feeds with the same code.
Now, go ahead and make RSS feeds for all your stuff. The world *needs* updates on your
goldfish!
Forcing the browser to download content
Sometimes you need your application to send content for download. For example, you can
generate a comma-separated values (CSV) file for your users to download and import into
their spreadsheet program.
Let's say you have an "Orders" controller which generates a CSV file in the "export"
action (i.e., "http://localhost:3000/orders/export"):
sub export : Local Args(0) {
my ( $self, $c ) = @_;
# In a real application, you'd generate this from the database
my $csv = "1,5.99\n2,29.99\n3,3.99\n";
$c->res->content_type('text/comma-separated-values');
$c->res->body($csv);
}
Normally the browser uses the last part of the URI to generate a filename for data it
cannot display. In this case your browser would likely ask you to save a file named
"export".
Luckily you can have the browser download the content with a specific filename by setting
the "Content-Disposition" header:
my $filename = 'Important Orders.csv';
$c->res->header('Content-Disposition', qq[attachment; filename="$filename"]);
Note the use of quotes around the filename; this ensures that any spaces in the filename
are handled by the browser.
Put this right before calling "$c->res->body" and your browser will download a file named
Important Orders.csv instead of "export".
You can also use this to have the browser download content which it normally displays,
such as JPEG images or even HTML. Just be sure to set the appropriate content type and
disposition.
Controllers
Controllers are the main point of communication between the web server and your
application. Here we explore some aspects of how they work.
Action Types
Introduction
A Catalyst application is driven by one or more Controller modules. There are a number of
ways that Catalyst can decide which of the methods in your controller modules it should
call. Controller methods are also called actions, because they determine how your catalyst
application should (re-)act to any given URL. When the application is started up, catalyst
looks at all your actions, and decides which URLs they map to.
Type attributes
Each action is a normal method in your controller, except that it has an attribute
attached. These can be one of several types.
Assume our Controller module starts with the following package declaration:
package MyApp::Controller::Buckets;
and we are running our application on localhost, port 3000 (the test server default).
Path
A Path attribute also takes an argument, this can be either a relative or an absolute
path. A relative path will be relative to the controller namespace, an absolute path
will represent an exact matching URL.
sub my_handles : Path('handles') { .. }
becomes
http://localhost:3000/buckets/handles
and
sub my_handles : Path('/handles') { .. }
becomes
http://localhost:3000/handles
See also: Catalyst::DispatchType::Path
Local
When using a Local attribute, no parameters are needed, instead, the name of the
action is matched in the URL. The namespaces created by the name of the controller
package is always part of the URL.
sub my_handles : Local { .. }
becomes
http://localhost:3000/buckets/my_handles
Global
A Global attribute is similar to a Local attribute, except that the namespace of the
controller is ignored, and matching starts at root.
sub my_handles : Global { .. }
becomes
http://localhost:3000/my_handles
Regex
By now you should have figured that a Regex attribute is just what it sounds like.
This one takes a regular expression, and matches starting from root. These differ from
the rest as they can match multiple URLs.
sub my_handles : Regex('^handles') { .. }
matches
http://localhost:3000/handles
and
http://localhost:3000/handles_and_other_parts
etc.
See also: Catalyst::DispatchType::Regex
LocalRegex
A LocalRegex is similar to a Regex, except it only matches below the current
controller namespace.
sub my_handles : LocalRegex(^handles') { .. }
matches
http://localhost:3000/buckets/handles
and
http://localhost:3000/buckets/handles_and_other_parts
etc.
Chained
See Catalyst::DispatchType::Chained for a description of how the chained dispatch type
works.
Private
Last but not least, there is the Private attribute, which allows you to create your
own internal actions, which can be forwarded to, but won't be matched as URLs.
sub my_handles : Private { .. }
becomes nothing at all..
Catalyst also predefines some special Private actions, which you can override, these
are:
default
The default action will be called, if no other matching action is found. If you
don't have one of these in your namespace, or any sub part of your namespace,
you'll get an error page instead. If you want to find out where it was the user
was trying to go, you can look in the request object using "$c->req->path".
sub default :Path { .. }
works for all unknown URLs, in this controller namespace, or every one if put
directly into MyApp.pm.
index
The index action is called when someone tries to visit the exact namespace of your
controller. If index, default and matching Path actions are defined, then index
will be used instead of default and Path.
sub index :Path :Args(0) { .. }
becomes
http://localhost:3000/buckets
begin
The begin action is called at the beginning of every request involving this
namespace directly, before other matching actions are called. It can be used to
set up variables/data for this particular part of your app. A single begin action
is called, its always the one most relevant to the current namespace.
sub begin : Private { .. }
is called once when
http://localhost:3000/bucket/(anything)?
is visited.
end Like begin, this action is always called for the namespace it is in, after every
other action has finished. It is commonly used to forward processing to the View
component. A single end action is called, its always the one most relevant to the
current namespace.
sub end : Private { .. }
is called once after any actions when
http://localhost:3000/bucket/(anything)?
is visited.
auto
Lastly, the auto action is magic in that every auto action in the chain of paths
up to and including the ending namespace, will be called. (In contrast, only one
of the begin/end/default actions will be called, the relevant one).
package MyApp::Controller::Root;
sub auto : Private { .. }
and
sub auto : Private { .. }
will both be called when visiting
http://localhost:3000/bucket/(anything)?
A word of warning
You can put root actions in your main MyApp.pm file, but this is deprecated, please put
your actions into your Root controller.
Flowchart
A graphical flowchart of how the dispatcher works can be found on the wiki at
<http://dev.catalystframework.org/attachment/wiki/WikiStart/catalyst-flow.png>.
DRY Controllers with Chained actions
Imagine that you would like the following paths in your application:
/cd/<ID>/track/<ID>
Displays info on a particular track.
In the case of a multi-volume CD, this is the track sequence.
/cd/<ID>/volume/<ID>/track/<ID>
Displays info on a track on a specific volume.
Here is some example code, showing how to do this with chained controllers:
package CD::Controller;
use base qw/Catalyst::Controller/;
sub root : Chained('/') PathPart('/cd') CaptureArgs(1) {
my ($self, $c, $cd_id) = @_;
$c->stash->{cd_id} = $cd_id;
$c->stash->{cd} = $self->model('CD')->find_by_id($cd_id);
}
sub trackinfo : Chained('track') PathPart('') Args(0) RenderView {
my ($self, $c) = @_;
}
package CD::Controller::ByTrackSeq;
use base qw/CD::Controller/;
sub track : Chained('root') PathPart('track') CaptureArgs(1) {
my ($self, $c, $track_seq) = @_;
$c->stash->{track} = $self->stash->{cd}->find_track_by_seq($track_seq);
}
package CD::Controller::ByTrackVolNo;
use base qw/CD::Controller/;
sub volume : Chained('root') PathPart('volume') CaptureArgs(1) {
my ($self, $c, $volume) = @_;
$c->stash->{volume} = $volume;
}
sub track : Chained('volume') PathPart('track') CaptureArgs(1) {
my ($self, $c, $track_no) = @_;
$c->stash->{track} = $self->stash->{cd}->find_track_by_vol_and_track_no(
$c->stash->{volume}, $track_no
);
}
Note that adding other actions (i.e. chain endpoints) which operate on a track is simply a
matter of adding a new sub to CD::Controller - no code is duplicated, even though there
are two different methods of looking up a track.
This technique can be expanded as needed to fulfil your requirements - for example, if you
inherit the first action of a chain from a base class, then mixing in a different base
class can be used to duplicate an entire URL hierarchy at a different point within your
application.
Component-based Subrequests
See Catalyst::Plugin::SubRequest.
File uploads
Single file upload with Catalyst
To implement uploads in Catalyst, you need to have a HTML form similar to this:
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="hidden" name="form_submit" value="yes">
<input type="file" name="my_file">
<input type="submit" value="Send">
</form>
It's very important not to forget "enctype="multipart/form-data"" in the form.
Catalyst Controller module 'upload' action:
sub upload : Global {
my ($self, $c) = @_;
if ( $c->request->parameters->{form_submit} eq 'yes' ) {
if ( my $upload = $c->request->upload('my_file') ) {
my $filename = $upload->filename;
my $target = "/tmp/upload/$filename";
unless ( $upload->link_to($target) || $upload->copy_to($target) ) {
die( "Failed to copy '$filename' to '$target': $!" );
}
}
}
$c->stash->{template} = 'file_upload.html';
}
Multiple file upload with Catalyst
Code for uploading multiple files from one form needs a few changes:
The form should have this basic structure:
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="hidden" name="form_submit" value="yes">
<input type="file" name="file1" size="50"><br>
<input type="file" name="file2" size="50"><br>
<input type="file" name="file3" size="50"><br>
<input type="submit" value="Send">
</form>
And in the controller:
sub upload : Local {
my ($self, $c) = @_;
if ( $c->request->parameters->{form_submit} eq 'yes' ) {
for my $field ( $c->req->upload ) {
my $upload = $c->req->upload($field);
my $filename = $upload->filename;
my $target = "/tmp/upload/$filename";
unless ( $upload->link_to($target) || $upload->copy_to($target) ) {
die( "Failed to copy '$filename' to '$target': $!" );
}
}
}
$c->stash->{template} = 'file_upload.html';
}
"for my $field ($c->req->upload)" loops automatically over all file input fields and gets
input names. After that is basic file saving code, just like in single file upload.
Notice: "die"ing might not be what you want to do, when an error occurs, but it works as
an example. A better idea would be to store error $! in "$c->stash->{error}" and show a
custom error template displaying this message.
For more information about uploads and usable methods look at Catalyst::Request::Upload
and Catalyst::Request.
Forwarding with arguments
Sometimes you want to pass along arguments when forwarding to another action. As of
version 5.30, arguments can be passed in the call to "forward"; in earlier versions, you
can manually set the arguments in the Catalyst Request object:
# version 5.30 and later:
$c->forward('/wherever', [qw/arg1 arg2 arg3/]);
# pre-5.30
$c->req->args([qw/arg1 arg2 arg3/]);
$c->forward('/wherever');
(See the Catalyst::Manual::Intro Flow_Control section for more information on passing
arguments via "forward".)
Chained dispatch using base classes, and inner packages.
package MyApp::Controller::Base;
use base qw/Catalyst::Controller/;
sub key1 : Chained('/')
Extending RenderView (formerly DefaultEnd)
The recommended approach for an "end" action is to use Catalyst::Action::RenderView
(taking the place of Catalyst::Plugin::DefaultEnd), which does what you usually need.
However there are times when you need to add a bit to it, but don't want to write your own
"end" action.
You can extend it like this:
To add something to an "end" action that is called before rendering (this is likely to be
what you want), simply place it in the "end" method:
sub end : ActionClass('RenderView') {
my ( $self, $c ) = @_;
# do stuff here; the RenderView action is called afterwards
}
To add things to an "end" action that are called after rendering, you can set it up like
this:
sub render : ActionClass('RenderView') { }
sub end : Private {
my ( $self, $c ) = @_;
$c->forward('render');
# do stuff here
}
Serving static content
Serving static content in Catalyst used to be somewhat tricky; the use of
Catalyst::Plugin::Static::Simple makes everything much easier. This plugin will
automatically serve your static content during development, but allows you to easily
switch to Apache (or other server) in a production environment.
Introduction to Static::Simple
Static::Simple is a plugin that will help to serve static content for your application. By
default, it will serve most types of files, excluding some standard Template Toolkit
extensions, out of your root file directory. All files are served by path, so if
images/me.jpg is requested, then root/images/me.jpg is found and served.
Usage
Using the plugin is as simple as setting your use line in MyApp.pm to include:
use Catalyst qw/Static::Simple/;
and already files will be served.
Configuring
Static content is best served from a single directory within your root directory. Having
many different directories such as root/css and root/images requires more code to manage,
because you must separately identify each static directory--if you decide to add a root/js
directory, you'll need to change your code to account for it. In contrast, keeping all
static directories as subdirectories of a main root/static directory makes things much
easier to manage. Here's an example of a typical root directory structure:
root/
root/content.tt
root/controller/stuff.tt
root/header.tt
root/static/
root/static/css/main.css
root/static/images/logo.jpg
root/static/js/code.js
All static content lives under root/static, with everything else being Template Toolkit
files.
Include Path
You may of course want to change the default locations, and make Static::Simple look
somewhere else, this is as easy as:
MyApp->config(
static => {
include_path => [
MyApp->path_to('/'),
'/path/to/my/files',
],
},
);
When you override include_path, it will not automatically append the normal root path,
so you need to add it yourself if you still want it. These will be searched in order
given, and the first matching file served.
Static directories
If you want to force some directories to be only static, you can set them using paths
relative to the root dir, or regular expressions:
MyApp->config(
static => {
dirs => [
'static',
qr/^(images|css)/,
],
},
);
File extensions
By default, the following extensions are not served (that is, they will be processed
by Catalyst): tmpl, tt, tt2, html, xhtml. This list can be replaced easily:
MyApp->config(
static => {
ignore_extensions => [
qw/tmpl tt tt2 html xhtml/
],
},
);
Ignoring directories
Entire directories can be ignored. If used with include_path, directories relative to
the include_path dirs will also be ignored:
MyApp->config( static => {
ignore_dirs => [ qw/tmpl css/ ],
});
More information
Catalyst::Plugin::Static::Simple
Serving manually with the Static plugin with HTTP::Daemon (myapp_server.pl)
In some situations you might want to control things more directly, using
Catalyst::Plugin::Static.
In your main application class (MyApp.pm), load the plugin:
use Catalyst qw/-Debug FormValidator Static OtherPlugin/;
You will also need to make sure your end method does not forward static content to the
view, perhaps like this:
sub end : Private {
my ( $self, $c ) = @_;
$c->forward( 'MyApp::View::TT' )
unless ( $c->res->body || !$c->stash->{template} );
}
This code will only forward to the view if a template has been previously defined by a
controller and if there is not already data in "$c->res->body".
Next, create a controller to handle requests for the /static path. Use the Helper to save
time. This command will create a stub controller as lib/MyApp/Controller/Static.pm.
$ script/myapp_create.pl controller Static
Edit the file and add the following methods:
# serve all files under /static as static files
sub default : Path('/static') {
my ( $self, $c ) = @_;
# Optional, allow the browser to cache the content
$c->res->headers->header( 'Cache-Control' => 'max-age=86400' );
$c->serve_static; # from Catalyst::Plugin::Static
}
# also handle requests for /favicon.ico
sub favicon : Path('/favicon.ico') {
my ( $self, $c ) = @_;
$c->serve_static;
}
You can also define a different icon for the browser to use instead of favicon.ico by
using this in your HTML header:
<link rel="icon" href="/static/myapp.ico" type="image/x-icon" />
Common problems with the Static plugin
The Static plugin makes use of the "shared-mime-info" package to automatically determine
MIME types. This package is notoriously difficult to install, especially on win32 and OS
X. For OS X the easiest path might be to install Fink, then use "apt-get install
shared-mime-info". Restart the server, and everything should be fine.
Make sure you are using the latest version (>= 0.16) for best results. If you are having
errors serving CSS files, or if they get served as text/plain instead of text/css, you may
have an outdated shared-mime-info version. You may also wish to simply use the following
code in your Static controller:
if ($c->req->path =~ /css$/i) {
$c->serve_static( "text/css" );
} else {
$c->serve_static;
}
Serving Static Files with Apache
When using Apache, you can bypass Catalyst and any Static plugins/controllers controller
by intercepting requests for the root/static path at the server level. All that is
required is to define a DocumentRoot and add a separate Location block for your static
content. Here is a complete config for this application under mod_perl 1.x:
<Perl>
use lib qw(/var/www/MyApp/lib);
</Perl>
PerlModule MyApp
<VirtualHost *>
ServerName myapp.example.com
DocumentRoot /var/www/MyApp/root
<Location />
SetHandler perl-script
PerlHandler MyApp
</Location>
<LocationMatch "/(static|favicon.ico)">
SetHandler default-handler
</LocationMatch>
</VirtualHost>
And here's a simpler example that'll get you started:
Alias /static/ "/my/static/files/"
<Location "/static">
SetHandler none
</Location>
Caching
Catalyst makes it easy to employ several different types of caching to speed up your
applications.
Cache Plugins
There are three wrapper plugins around common CPAN cache modules: Cache::FastMmap,
Cache::FileCache, and Cache::Memcached. These can be used to cache the result of slow
operations.
The Catalyst Advent Calendar uses the FileCache plugin to cache the rendered XHTML version
of the source POD document. This is an ideal application for a cache because the source
document changes infrequently but may be viewed many times.
use Catalyst qw/Cache::FileCache/;
...
use File::stat;
sub render_pod : Local {
my ( self, $c ) = @_;
# the cache is keyed on the filename and the modification time
# to check for updates to the file.
my $file = $c->path_to( 'root', '2005', '11.pod' );
my $mtime = ( stat $file )->mtime;
my $cached_pod = $c->cache->get("$file $mtime");
if ( !$cached_pod ) {
$cached_pod = do_slow_pod_rendering();
# cache the result for 12 hours
$c->cache->set( "$file $mtime", $cached_pod, '12h' );
}
$c->stash->{pod} = $cached_pod;
}
We could actually cache the result forever, but using a value such as 12 hours allows old
entries to be automatically expired when they are no longer needed.
Page Caching
Another method of caching is to cache the entire HTML page. While this is traditionally
handled by a frontend proxy server like Squid, the Catalyst PageCache plugin makes it
trivial to cache the entire output from frequently-used or slow actions.
Many sites have a busy content-filled front page that might look something like this. It
probably takes a while to process, and will do the exact same thing for every single user
who views the page.
sub front_page : Path('/') {
my ( $self, $c ) = @_;
$c->forward( 'get_news_articles' );
$c->forward( 'build_lots_of_boxes' );
$c->forward( 'more_slow_stuff' );
$c->stash->{template} = 'index.tt';
}
We can add the PageCache plugin to speed things up.
use Catalyst qw/Cache::FileCache PageCache/;
sub front_page : Path ('/') {
my ( $self, $c ) = @_;
$c->cache_page( 300 );
# same processing as above
}
Now the entire output of the front page, from <html> to </html>, will be cached for 5
minutes. After 5 minutes, the next request will rebuild the page and it will be re-
cached.
Note that the page cache is keyed on the page URI plus all parameters, so requests for /
and /?foo=bar will result in different cache items. Also, only GET requests will be
cached by the plugin.
You can even get that frontend Squid proxy to help out by enabling HTTP headers for the
cached page.
MyApp->config(
page_cache => {
set_http_headers => 1,
},
);
This would now set the following headers so proxies and browsers may cache the content
themselves.
Cache-Control: max-age=($expire_time - time)
Expires: $expire_time
Last-Modified: $cache_created_time
Template Caching
Template Toolkit provides support for caching compiled versions of your templates. To
enable this in Catalyst, use the following configuration. TT will cache compiled
templates keyed on the file mtime, so changes will still be automatically detected.
package MyApp::View::TT;
use strict;
use warnings;
use base 'Catalyst::View::TT';
__PACKAGE__->config(
COMPILE_DIR => '/tmp/template_cache',
);
1;
More Info
See the documentation for each cache plugin for more details and other available
configuration options.
Catalyst::Plugin::Cache::FastMmap Catalyst::Plugin::Cache::FileCache
Catalyst::Plugin::Cache::Memcached Catalyst::Plugin::PageCache "Caching and Compiling
Options" in Template::Manual::Config
Testing
Testing is an integral part of the web application development process. Tests make multi
developer teams easier to coordinate, and they help ensure that there are no nasty
surprises after upgrades or alterations.
Testing
Catalyst provides a convenient way of testing your application during development and
before deployment in a real environment.
Catalyst::Test makes it possible to run the same tests both locally (without an external
daemon) and against a remote server via HTTP.
Tests
Let's examine a skeleton application's t/ directory:
mundus:~/MyApp chansen$ ls -l t/
total 24
-rw-r--r-- 1 chansen chansen 95 18 Dec 20:50 01app.t
-rw-r--r-- 1 chansen chansen 190 18 Dec 20:50 02pod.t
-rw-r--r-- 1 chansen chansen 213 18 Dec 20:50 03podcoverage.t
01app.t
Verifies that the application loads, compiles, and returns a successful response.
02pod.t
Verifies that all POD is free from errors. Only executed if the "TEST_POD" environment
variable is true.
03podcoverage.t
Verifies that all methods/functions have POD coverage. Only executed if the "TEST_POD"
environment variable is true.
Creating tests
mundus:~/MyApp chansen$ cat t/01app.t | perl -ne 'printf( "%2d %s", $., $_ )'
1 use Test::More tests => 2;
2 BEGIN { use_ok( Catalyst::Test, 'MyApp' ) }
3
4 ok( request('/')->is_success );
The first line declares how many tests we are going to run, in this case two. The second
line tests and loads our application in test mode. The fourth line verifies that our
application returns a successful response.
Catalyst::Test exports two functions, "request" and "get". Each can take three different
arguments:
A string which is a relative or absolute URI.
request('/my/path');
request('http://www.host.com/my/path');
An instance of URI.
request( URI->new('http://www.host.com/my/path') );
An instance of HTTP::Request.
request( HTTP::Request->new( GET => 'http://www.host.com/my/path') );
"request" returns an instance of HTTP::Response and "get" returns the content (body) of
the response.
Running tests locally
mundus:~/MyApp chansen$ CATALYST_DEBUG=0 TEST_POD=1 prove --lib lib/ t/
t/01app............ok
t/02pod............ok
t/03podcoverage....ok
All tests successful.
Files=3, Tests=4, 2 wallclock secs ( 1.60 cusr + 0.36 csys = 1.96 CPU)
"CATALYST_DEBUG=0" ensures that debugging is off; if it's enabled you will see debug logs
between tests.
"TEST_POD=1" enables POD checking and coverage.
"prove" A command-line tool that makes it easy to run tests. You can find out more about
it from the links below.
Running tests remotely
mundus:~/MyApp chansen$ CATALYST_SERVER=http://localhost:3000/ prove --lib lib/ t/01app.t
t/01app....ok
All tests successful.
Files=1, Tests=2, 0 wallclock secs ( 0.40 cusr + 0.01 csys = 0.41 CPU)
"CATALYST_SERVER=http://localhost:3000/" is the absolute deployment URI of your
application. In "CGI" or "FastCGI" it should be the host and path to the script.
Test::WWW::Mechanize and Catalyst
Be sure to check out Test::WWW::Mechanize::Catalyst. It makes it easy to test HTML, forms
and links. A short example of usage:
use Test::More tests => 6;
BEGIN { use_ok( Test::WWW::Mechanize::Catalyst, 'MyApp' ) }
my $mech = Test::WWW::Mechanize::Catalyst->new;
$mech->get_ok("http://localhost/", 'Got index page');
$mech->title_like( qr/^MyApp on Catalyst/, 'Got right index title' );
ok( $mech->find_link( text_regex => qr/^Wiki/i ), 'Found link to Wiki' );
ok( $mech->find_link( text_regex => qr/^Mailing-List/i ), 'Found link to Mailing-List' );
ok( $mech->find_link( text_regex => qr/^IRC channel/i ), 'Found link to IRC channel' );
Further Reading
• Catalyst::Test
• Test::WWW::Mechanize::Catalyst
• Test::WWW::Mechanize
• WWW::Mechanize
• LWP::UserAgent
• HTML::Form
• HTTP::Message
• HTTP::Request
• HTTP::Request::Common
• HTTP::Response
• HTTP::Status
• URI
• Test::More
• Test::Pod
• Test::Pod::Coverage
• prove (Test::Harness)
More Information
• Catalyst::Plugin::Authorization::Roles
• Catalyst::Plugin::Authorization::ACL
AUTHORS
Catalyst Contributors, see Catalyst.pm
COPYRIGHT
This library is free software. You can redistribute it and/or modify it under the same
terms as Perl itself.