plucky (3) Catalyst::Manual::Cookbook.3pm.gz
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
<https://web.archive.org/web/20190919010727/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.