NAME

Catalyst - The Elegant MVC Web Application Framework

SYNOPSIS

See the Catalyst::Manual distribution for comprehensive documentation and tutorials.

# Install Catalyst::Devel for helpers and other development tools
# use the helper to create a new application
catalyst.pl MyApp

# add models, views, controllers
script/myapp_create.pl model MyDatabase DBIC::Schema create=static dbi:SQLite:/path/to/db
script/myapp_create.pl view MyTemplate TT
script/myapp_create.pl controller Search

# built in testserver -- use -r to restart automatically on changes
# --help to see all available options
script/myapp_server.pl

# command line testing interface
script/myapp_test.pl /yada

### in lib/MyApp.pm
use Catalyst qw/-Debug/; # include plugins here as well

### In lib/MyApp/Controller/Root.pm (autocreated)
sub foo : Chained('/') Args() { # called for /foo, /foo/1, /foo/1/2, etc.
    my ( $self, $c, @args ) = @_; # args are qw/1 2/ for /foo/1/2
    $c->stash->{template} = 'foo.tt'; # set the template
    # lookup something from db -- stash vars are passed to TT
    $c->stash->{data} =
      $c->model('Database::Foo')->search( { country => $args[0] } );
    if ( $c->req->params->{bar} ) { # access GET or POST parameters
        $c->forward( 'bar' ); # process another action
        # do something else after forward returns
    }
}

# The foo.tt TT template can use the stash data from the database
[% WHILE (item = data.next) %]
    [% item.foo %]
[% END %]

# called for /bar/of/soap, /bar/of/soap/10, etc.
sub bar : Chained('/') PathPart('/bar/of/soap') Args() { ... }

# called after all actions are finished
sub end : Action {
    my ( $self, $c ) = @_;
    if ( scalar @{ $c->error } ) { ... } # handle errors
    return if $c->res->body; # already have a response
    $c->forward( 'MyApp::View::TT' ); # render template
}

See Catalyst::Manual::Intro for additional information.

DESCRIPTION

Catalyst is a modern framework for making web applications without the pain usually associated with this process. This document is a reference to the main Catalyst application. If you are a new user, we suggest you start with Catalyst::Manual::Tutorial or Catalyst::Manual::Intro.

See Catalyst::Manual for more documentation.

Catalyst plugins can be loaded by naming them as arguments to the "use Catalyst" statement. Omit the Catalyst::Plugin:: prefix from the plugin name, i.e., Catalyst::Plugin::My::Module becomes My::Module.

use Catalyst qw/My::Module/;

If your plugin starts with a name other than Catalyst::Plugin::, you can fully qualify the name by using a unary plus:

use Catalyst qw/
    My::Module
    +Fully::Qualified::Plugin::Name
/;

Special flags like -Debug can also be specified as arguments when Catalyst is loaded:

use Catalyst qw/-Debug My::Module/;

The position of plugins and flags in the chain is important, because they are loaded in the order in which they appear.

The following flags are supported:

-Debug

Enables debug output. You can also force this setting from the system environment with CATALYST_DEBUG or <MYAPP>_DEBUG. The environment settings override the application, with <MYAPP>_DEBUG having the highest priority.

This sets the log level to 'debug' and enables full debug output on the error screen. If you only want the latter, see $c->debug.

-Home

Forces Catalyst to use a specific home directory, e.g.:

use Catalyst qw[-Home=/usr/mst];

This can also be done in the shell environment by setting either the CATALYST_HOME environment variable or MYAPP_HOME; where MYAPP is replaced with the uppercased name of your application, any "::" in the name will be replaced with underscores, e.g. MyApp::Web should use MYAPP_WEB_HOME. If both variables are set, the MYAPP_HOME one will be used.

If none of these are set, Catalyst will attempt to automatically detect the home directory. If you are working in a development environment, Catalyst will try and find the directory containing either Makefile.PL, Build.PL, dist.ini, or cpanfile. If the application has been installed into the system (i.e. you have done make install), then Catalyst will use the path to your application module, without the .pm extension (e.g., /foo/MyApp if your application was installed at /foo/MyApp.pm)

-Log

use Catalyst '-Log=warn,fatal,error';

Specifies a comma-delimited list of log levels.

-Stats

Enables statistics collection and reporting.

use Catalyst qw/-Stats=1/;

You can also force this setting from the system environment with CATALYST_STATS or <MYAPP>_STATS. The environment settings override the application, with <MYAPP>_STATS having the highest priority.

Stats are also enabled if debugging is enabled.

METHODS

INFORMATION ABOUT THE CURRENT REQUEST

$c->action

Returns a Catalyst::Action object for the current action, which stringifies to the action name. See Catalyst::Action.

$c->namespace

Returns the namespace of the current action, i.e., the URI prefix corresponding to the controller of the current action. For example:

# in Controller::Foo::Bar
$c->namespace; # returns 'foo/bar';

$c->request

$c->req

Returns the current Catalyst::Request object, giving access to information about the current client request (including parameters, cookies, HTTP headers, etc.). See Catalyst::Request.

REQUEST FLOW HANDLING

$c->forward( $action [, \@arguments ] )

$c->forward( $class, $method, [, \@arguments ] )

This is one way of calling another action (method) in the same or a different controller. You can also use $self->my_method($c, @args) in the same controller or $c->controller('MyController')->my_method($c, @args) in a different controller. The main difference is that 'forward' uses some of the Catalyst request cycle overhead, including debugging, which may be useful to you. On the other hand, there are some complications to using 'forward', restrictions on values returned from 'forward', and it may not handle errors as you prefer. Whether you use 'forward' or not is up to you; it is not considered superior to the other ways to call a method.

'forward' calls another action, by its private name. If you give a class name but no method, process() is called. You may also optionally pass arguments in an arrayref. The action will receive the arguments in @_ and $c->req->args. Upon returning from the function, $c->req->args will be restored to the previous values.

Any data returned from the action forwarded to, will be returned by the call to forward.

my $foodata = $c->forward('/foo');
$c->forward('index');
$c->forward(qw/Model::DBIC::Foo do_stuff/);
$c->forward('View::TT');

Note that forward implies an eval { } around the call (actually execute does), thus rendering all exceptions thrown by the called action non-fatal and pushing them onto $c->error instead. If you want die to propagate you need to do something like:

$c->forward('foo');
die join "\n", @{ $c->error } if @{ $c->error };

Or make sure to always return true values from your actions and write your code like this:

$c->forward('foo') || return;

Another note is that $c->forward always returns a scalar because it actually returns $c->state which operates in a scalar context. Thus, something like:

return @array;

in an action that is forwarded to is going to return a scalar, i.e. how many items are in that array, which is probably not what you want. If you need to return an array then return a reference to it, or stash it like so:

$c->stash->{array} = \@array;

and access it from the stash.

Keep in mind that the end method used is that of the caller action. So a $c->detach inside a forwarded action would run the end method from the original action requested.

$c->detach( $action [, \@arguments ] )

$c->detach( $class, $method, [, \@arguments ] )

$c->detach()

The same as forward, but doesn't return to the previous action when processing is finished.

When called with no arguments it escapes the processing chain entirely.

$c->visit( $action [, \@arguments ] )

$c->visit( $action [, \@captures, \@arguments ] )

$c->visit( $class, $method, [, \@arguments ] )

$c->visit( $class, $method, [, \@captures, \@arguments ] )

Almost the same as forward, but does a full dispatch, instead of just calling the new $action / $class->$method. This means that begin, auto and the method you go to are called, just like a new request.

In addition both $c->action and $c->namespace are localized. This means, for example, that $c->action methods such as name, class and reverse return information for the visited action when they are invoked within the visited action. This is different from the behavior of forward, which continues to use the $c->action object from the caller action even when invoked from the called action.

$c->stash is kept unchanged.

In effect, visit allows you to "wrap" another action, just as it would have been called by dispatching from a URL, while the analogous go allows you to transfer control to another action as if it had been reached directly from a URL.

$c->go( $action [, \@arguments ] )

$c->go( $action [, \@captures, \@arguments ] )

$c->go( $class, $method, [, \@arguments ] )

$c->go( $class, $method, [, \@captures, \@arguments ] )

The relationship between go and visit is the same as the relationship between forward and detach. Like $c->visit, $c->go will perform a full dispatch on the specified action or method, with localized $c->action and $c->namespace. Like detach, go escapes the processing of the current request chain on completion, and does not return to its caller.

@arguments are arguments to the final destination of $action. @captures are arguments to the intermediate steps, if any, on the way to the final sub of $action.

$c->response

$c->res

Returns the current Catalyst::Response object, see there for details.

$c->stash

Returns a hashref to the stash, which may be used to store data and pass it between components during a request. You can also set hash keys by passing arguments. The stash is automatically sent to the view. The stash is cleared at the end of a request; it cannot be used for persistent storage (for this you must use a session; see Catalyst::Plugin::Session for a complete system integrated with Catalyst).

$c->stash->{foo} = $bar;
$c->stash( { moose => 'majestic', qux => 0 } );
$c->stash( bar => 1, gorch => 2 ); # equivalent to passing a hashref

# stash is automatically passed to the view for use in a template
$c->forward( 'MyApp::View::TT' );

$c->error

$c->error($error, ...)

$c->error($arrayref)

Returns an arrayref containing error messages. If Catalyst encounters an error while processing a request, it stores the error in $c->error. This method should only be used to store fatal error messages.

my @error = @{ $c->error };

Add a new error.

$c->error('Something bad happened');

$c->state

Contains the return value of the last executed action. Note that << $c->state >> operates in a scalar context which means that all values it returns are scalar.

$c->clear_errors

Clear errors. You probably don't want to clear the errors unless you are implementing a custom error screen.

This is equivalent to running

$c->error(0);

$c->has_errors

Returns true if you have errors

COMPONENT ACCESSORS

$c->controller($name)

Gets a Catalyst::Controller instance by name.

$c->controller('Foo')->do_stuff;

If the name is omitted, will return the controller for the dispatched action.

If you want to search for controllers, pass in a regexp as the argument.

# find all controllers that start with Foo
my @foo_controllers = $c->controller(qr{^Foo});

$c->model($name)

Gets a Catalyst::Model instance by name.

$c->model('Foo')->do_stuff;

Any extra arguments are directly passed to ACCEPT_CONTEXT.

If the name is omitted, it will look for - a model object in $c->stash->{current_model_instance}, then - a model name in $c->stash->{current_model}, then - a config setting 'default_model', or - check if there is only one model, and return it if that's the case.

If you want to search for models, pass in a regexp as the argument.

# find all models that start with Foo
my @foo_models = $c->model(qr{^Foo});

$c->view($name)

Gets a Catalyst::View instance by name.

$c->view('Foo')->do_stuff;

Any extra arguments are directly passed to ACCEPT_CONTEXT.

If the name is omitted, it will look for - a view object in $c->stash->{current_view_instance}, then - a view name in $c->stash->{current_view}, then - a config setting 'default_view', or - check if there is only one view, and return it if that's the case.

If you want to search for views, pass in a regexp as the argument.

# find all views that start with Foo
my @foo_views = $c->view(qr{^Foo});

$c->controllers

Returns the available names which can be passed to $c->controller

$c->models

Returns the available names which can be passed to $c->model

$c->views

Returns the available names which can be passed to $c->view

$c->comp($name)

$c->component($name)

Gets a component object by name. This method is not recommended, unless you want to get a specific component by full class. $c->controller, $c->model, and $c->view should be used instead.

If $name is a regexp, a list of components matched against the full component name will be returned.

If Catalyst can't find a component by name, it will fallback to regex matching by default. To disable this behaviour set disable_component_resolution_regex_fallback to a true value.

__PACKAGE__->config( disable_component_resolution_regex_fallback => 1 );

CLASS DATA AND HELPER CLASSES

$c->config

Returns or takes a hashref containing the application's configuration.

__PACKAGE__->config( { db => 'dsn:SQLite:foo.db' } );

You can also use a YAML, XML or Config::General config file like myapp.conf in your applications home directory. See Catalyst::Plugin::ConfigLoader.

Cascading configuration

The config method is present on all Catalyst components, and configuration will be merged when an application is started. Configuration loaded with Catalyst::Plugin::ConfigLoader takes precedence over other configuration, followed by configuration in your top level MyApp class. These two configurations are merged, and then configuration data whose hash key matches a component name is merged with configuration for that component.

The configuration for a component is then passed to the new method when a component is constructed.

For example:

MyApp->config({ 'Model::Foo' => { bar => 'baz', overrides => 'me' } });
MyApp::Model::Foo->config({ quux => 'frob', overrides => 'this' });

will mean that MyApp::Model::Foo receives the following data when constructed:

MyApp::Model::Foo->new({
    bar => 'baz',
    quux => 'frob',
    overrides => 'me',
});

It's common practice to use a Moose attribute on the receiving component to access the config value.

package MyApp::Model::Foo;

use Moose;

# this attr will receive 'baz' at construction time
has 'bar' => (
    is  => 'rw',
    isa => 'Str',
);

You can then get the value 'baz' by calling $c->model('Foo')->bar (or $self->bar inside code in the model).

NOTE: you MUST NOT call $self->config or __PACKAGE__->config as a way of reading config within your code, as this will not give you the correctly merged config back. You MUST take the config values supplied to the constructor and use those instead.

$c->log

Returns the logging object instance. Unless it is already set, Catalyst sets this up with a Catalyst::Log object. To use your own log class, set the logger with the __PACKAGE__->log method prior to calling __PACKAGE__->setup.

__PACKAGE__->log( MyLogger->new );
__PACKAGE__->setup;

And later:

$c->log->info( 'Now logging with my own logger!' );

Your log class should implement the methods described in Catalyst::Log.

encoding

Sets or gets the application encoding.

$c->debug

Returns 1 if debug mode is enabled, 0 otherwise.

You can enable debug mode in several ways:

By calling myapp_server.pl with the -d flag

With the environment variables MYAPP_DEBUG, or CATALYST_DEBUG

The -Debug option in your MyApp.pm

By declaring sub debug { 1 } in your MyApp.pm.

The first three also set the log level to 'debug'.

Calling $c->debug(1) has no effect.

$c->dispatcher

Returns the dispatcher instance. See Catalyst::Dispatcher.

$c->engine

Returns the engine instance. See Catalyst::Engine.

UTILITY METHODS

$c->path_to(@path)

Merges @path with $c->config->{home} and returns a Path::Class::Dir object. Note you can usually use this object as a filename, but sometimes you will have to explicitly stringify it yourself by calling the ->stringify method.

For example:

$c->path_to( 'db', 'sqlite.db' );

MyApp->setup

Initializes the dispatcher and engine, loads any plugins, and loads the model, view, and controller components. You may also specify an array of plugins to load here, if you choose to not load them in the use Catalyst line.

MyApp->setup;
MyApp->setup( qw/-Debug/ );

Note: You should not wrap this method with method modifiers or bad things will happen - wrap the setup_finalize method instead.

$app->setup_finalize

A hook to attach modifiers to. This method does not do anything except set the setup_finished accessor.

Applying method modifiers to the setup method doesn't work, because of quirky things done for plugin setup.

Example:

after setup_finalize => sub {
    my $app = shift;

    ## do stuff here..
};

$c->uri_for( $path?, @args?, \%query_values? )

$c->uri_for( $action, \@captures?, @args?, \%query_values? )

Constructs an absolute URI object based on the application root, the provided path, and the additional arguments and query parameters provided. When used as a string, provides a textual URI. If you need more flexibility than this (i.e. the option to provide relative URIs etc.) see Catalyst::Plugin::SmartURI.

If no arguments are provided, the URI for the current action is returned. To return the current action and also provide @args, use $c->uri_for( $c->action, @args ).

If the first argument is a string, it is taken as a public URI path relative to $c->namespace (if it doesn't begin with a forward slash) or relative to the application root (if it does). It is then merged with $c->request->base; any @args are appended as additional path components; and any %query_values are appended as ?foo=bar parameters.

If the first argument is a Catalyst::Action it represents an action which will have its path resolved using $c->dispatcher->uri_for_action. The optional \@captures argument (an arrayref) allows passing the captured variables that are needed to fill in the paths of Chained and Regex actions; once the path is resolved, uri_for continues as though a path was provided, appending any arguments or parameters and creating an absolute URI.

The captures for the current request can be found in $c->request->captures, and actions can be resolved using Catalyst::Controller->action_for($name). If you have a private action path, use $c->uri_for_action instead.

# Equivalent to $c->req->uri
$c->uri_for($c->action, $c->req->captures,
    @{ $c->req->args }, $c->req->params);

# For the Foo action in the Bar controller
$c->uri_for($c->controller('Bar')->action_for('Foo'));

# Path to a static resource
$c->uri_for('/static/images/logo.png');

$c->uri_for_action( $path, \@captures_and_args?, @args?, \%query_values? )

$c->uri_for_action( $action, \@captures_and_args?, @args?, \%query_values? )

$path

A private path to the Catalyst action you want to create a URI for.

This is a shortcut for calling $c->dispatcher->get_action_by_path($path) and passing the resulting $action and the remaining arguments to $c->uri_for.

You can also pass in a Catalyst::Action object, in which case it is passed to $c->uri_for.

Note that although the path looks like a URI that dispatches to the wanted action, it is not a URI, but an internal path to that action.

For example, if the action looks like:

package MyApp::Controller::Users;

sub lst : Path('the-list') {}

You can use:

$c->uri_for_action('/users/lst')

and it will create the URI /users/the-list.

\@captures_and_args?

Optional array reference of Captures (i.e. <CaptureArgs or $c-req->captures>) and arguments to the request. Usually used with Catalyst::DispatchType::Chained to interpolate all the parameters in the URI.

@args?

Optional list of extra arguments - can be supplied in the \@captures_and_args? array ref, or here - whichever is easier for your code.

Your action can have zero, a fixed or a variable number of args (e.g. Args(1) for a fixed number or Args() for a variable number)..

\%query_values?

Optional array reference of query parameters to append. E.g.

{ foo => 'bar' }

will generate

/rest/of/your/uri?foo=bar

$c->welcome_message

Returns the Catalyst welcome HTML page.

run_options

Contains a hash of options passed from the application script, including the original ARGV the script received, the processed values from that ARGV and any extra arguments to the script which were not processed.

This can be used to add custom options to your application's scripts and setup your application differently depending on the values of these options.

INTERNAL METHODS

These methods are not meant to be used by end users.

$c->components

Returns a hash of components.

$c->context_class

Returns or sets the context class.

$c->counter

Returns a hashref containing coderefs and execution counts (needed for deep recursion detection).

$c->depth

Returns the number of actions on the current internal execution stack.

$c->dispatch

Dispatches a request to actions.

$c->dispatcher_class

Returns or sets the dispatcher class.

$c->dump_these

Returns a list of 2-element array references (name, structure) pairs that will be dumped on the error page in debug mode.

$c->engine_class

Returns or sets the engine class.

$c->execute( $class, $coderef )

Execute a coderef in given class and catch exceptions. Errors are available via $c->error.

$c->finalize

Finalizes the request.

$c->finalize_body

Finalizes body.

$c->finalize_cookies

Finalizes cookies.

$c->finalize_error

Finalizes error. If there is only one error in "error" and it is an object that does as_psgi or code we rethrow the error and presume it caught by middleware up the ladder. Otherwise we return the debugging error page (in debug mode) or we return the default error page (production mode).

$c->finalize_headers

Finalizes headers.

$c->finalize_encoding

Make sure your headers and body are encoded properly IF you set an encoding. See "ENCODING".

$c->finalize_output

An alias for finalize_body.

$c->finalize_read

Finalizes the input after reading is complete.

$c->finalize_uploads

Finalizes uploads. Cleans up any temporary files.

$c->get_action( $action, $namespace )

Gets an action in a given namespace.

$c->get_actions( $action, $namespace )

Gets all actions of a given name in a namespace and all parent namespaces.

$app->handle_request( @arguments )

Called to handle each HTTP request.

$class->prepare( @arguments )

Creates a Catalyst context from an engine-specific request (Apache, CGI, etc.).

$c->prepare_action

Prepares action. See Catalyst::Dispatcher.

$c->prepare_body

Prepares message body.

$c->prepare_body_chunk( $chunk )

Prepares a chunk of data before sending it to HTTP::Body.

See Catalyst::Engine.

$c->prepare_body_parameters

Prepares body parameters.

$c->prepare_connection

Prepares connection.

$c->prepare_cookies

Prepares cookies by ensuring that the attribute on the request object has been built.

$c->prepare_headers

Prepares request headers by ensuring that the attribute on the request object has been built.

$c->prepare_parameters

Prepares parameters.

$c->prepare_path

Prepares path and base.

$c->prepare_query_parameters

Prepares query parameters.

$c->log_request

Writes information about the request to the debug logs. This includes:

• Request method, path, and remote IP address

• Query keywords (see "query_keywords" in Catalyst::Request)

• Request parameters

• File uploads

$c->log_response

Writes information about the response to the debug logs by calling $c->log_response_status_line and $c->log_response_headers.

$c->log_response_status_line($response)

Writes one line of information about the response to the debug logs. This includes:

• Response status code

• Content-Type header (if present)

• Content-Length header (if present)

$c->log_response_headers($headers);

Hook method which can be wrapped by plugins to log the response headers. No-op in the default implementation.

$c->log_request_parameters( query => {}, body => {} )

Logs request parameters to debug logs

$c->log_request_uploads

Logs file uploads included in the request to the debug logs. The parameter name, filename, file type, and file size are all included in the debug logs.

$c->log_request_headers($headers);

Hook method which can be wrapped by plugins to log the request headers. No-op in the default implementation.

$c->log_headers($type => $headers)

Logs HTTP::Headers (either request or response) to the debug logs.

$c->prepare_read

Prepares the input for reading.

$c->prepare_request

Prepares the engine request.

$c->prepare_uploads

Prepares uploads.

$c->prepare_write

Prepares the output for writing.

$c->request_class

Returns or sets the request class. Defaults to Catalyst::Request.

$c->response_class

Returns or sets the response class. Defaults to Catalyst::Response.

$c->read( [$maxlength] )

Reads a chunk of data from the request body. This method is designed to be used in a while loop, reading $maxlength bytes on every call. $maxlength defaults to the size of the request if not specified.

You have to set MyApp->config(parse_on_demand => 1) to use this directly.

Warning: If you use read(), Catalyst will not process the body, so you will not be able to access POST parameters or file uploads via $c->request. You must handle all body parsing yourself.

$c->run

Starts the engine.

$c->set_action( $action, $code, $namespace, $attrs )

Sets an action in a given namespace.

$c->setup_actions($component)

Sets up actions for a component.

$c->setup_components

This method is called internally to set up the application's components.

It finds modules by calling the locate_components method, expands them to package names with the expand_component_module method, and then installs each component into the application.

The setup_components config option is passed to both of the above methods.

Installation of each component is performed by the setup_component method, below.

$c->locate_components( $setup_component_config )

This method is meant to provide a list of component modules that should be setup for the application. By default, it will use Module::Pluggable.

Specify a setup_components config option to pass additional options directly to Module::Pluggable. To add additional search paths, specify a key named search_extra as an array reference. Items in the array beginning with :: will have the application class name prepended to them.

$c->expand_component_module( $component, $setup_component_config )

Components found by locate_components will be passed to this method, which is expected to return a list of component (package) names to be set up.

$c->setup_component

$c->setup_dispatcher

Sets up dispatcher.

$c->setup_engine

Sets up engine.

$c->apply_default_middlewares

Adds the following Plack middlewares to your application, since they are useful and commonly needed:

Plack::Middleware::ReverseProxy, (conditionally added based on the status of your $ENV{REMOTE_ADDR}, and can be forced on with using_frontend_proxy or forced off with ignore_frontend_proxy), Plack::Middleware::LighttpdScriptNameFix (if you are using Lighttpd), Plack::Middleware::IIS6ScriptNameFix (always applied since this middleware is smart enough to conditionally apply itself).

Additionally if we detect we are using Nginx, we add a bit of custom middleware to solve some problems with the way that server handles $ENV{PATH_INFO} and $ENV{SCRIPT_NAME}

$c->psgi_app

Returns a PSGI application code reference for the catalyst application $c. This is the bare application without any middlewares applied. ${myapp}.psgi is not taken into account.

This is what you want to be using to retrieve the PSGI application code reference of your Catalyst application for use in .psgi files.

$c->setup_home

Sets up the home directory.

$c->setup_encoding

Sets up the input/output encoding. See ENCODING

handle_unicode_encoding_exception

Hook to let you customize how encoding errors are handled. By default we just throw an exception. Receives a hashref of debug information. Example:

$c->handle_unicode_encoding_exception({
    param_value => $value,
    error_msg => $_,
        encoding_step => 'params',
    });

$c->setup_log

Sets up log by instantiating a Catalyst::Log object and passing it to log(). Pass in a comma-delimited list of levels to set the log to.

This method also installs a debug method that returns a true value into the catalyst subclass if the "debug" level is passed in the comma-delimited list, or if the $CATALYST_DEBUG environment variable is set to a true value.

Note that if the log has already been setup, by either a previous call to setup_log or by a call such as __PACKAGE__->log( MyLogger->new ), that this method won't actually set up the log object.

$c->setup_plugins

Sets up plugins.

$c->setup_stats

Sets up timing statistics class.

$c->registered_plugins

Returns a sorted list of the plugins which have either been stated in the import list.

If passed a given plugin name, it will report a boolean value indicating whether or not that plugin is loaded. A fully qualified name is required if the plugin name does not begin with Catalyst::Plugin::.

if ($c->registered_plugins('Some::Plugin')) {
    ...
}

registered_middlewares

Read only accessor that returns an array of all the middleware in the order that they were added (which is the REVERSE of the order they will be applied).

The values returned will be either instances of Plack::Middleware or of a compatible interface, or a coderef, which is assumed to be inlined middleware

setup_middleware (?@middleware)

Read configuration information stored in configuration key psgi_middleware or from passed @args.

See under "CONFIGURATION" information regarding psgi_middleware and how to use it to enable Plack::Middleware

This method is automatically called during 'setup' of your application, so you really don't need to invoke it. However you may do so if you find the idea of loading middleware via configuration weird :). For example:

package MyApp;

use Catalyst;

__PACKAGE__->setup_middleware('Head');
__PACKAGE__->setup;

When we read middleware definitions from configuration, we reverse the list which sounds odd but is likely how you expect it to work if you have prior experience with Plack::Builder or if you previously used the plugin Catalyst::Plugin::EnableMiddleware (which is now considered deprecated)

So basically your middleware handles an incoming request from the first registered middleware, down and handles the response from the last middleware up.

registered_data_handlers

A read only copy of registered Data Handlers returned as a Hash, where each key is a content type and each value is a subref that attempts to decode that content type.

setup_data_handlers (?@data_handler)

Read configuration information stored in configuration key data_handlers or from passed @args.

See under "CONFIGURATION" information regarding data_handlers.

This method is automatically called during 'setup' of your application, so you really don't need to invoke it.

default_data_handlers

Default Data Handlers that come bundled with Catalyst. Currently there are only two default data handlers, for 'application/json' and an alternative to 'application/x-www-form-urlencoded' which supposed nested form parameters via CGI::Struct or via CGI::Struct::XS IF you've installed it.

The 'application/json' data handler is used to parse incoming JSON into a Perl data structure. It used either JSON::MaybeXS or JSON, depending on which is installed. This allows you to fail back to JSON:PP, which is a Pure Perl JSON decoder, and has the smallest dependency impact.

Because we don't wish to add more dependencies to Catalyst, if you wish to use this new feature we recommend installing JSON or JSON::MaybeXS in order to get the best performance. You should add either to your dependency list (Makefile.PL, dist.ini, cpanfile, etc.)

$c->stack

Returns an arrayref of the internal execution stack (actions that are currently executing).

$c->stats

Returns the current timing statistics object. By default Catalyst uses Catalyst::Stats, but can be set otherwise with stats_class.

Even if -Stats is not enabled, the stats object is still available. By enabling it with $c-stats->enabled(1) >, it can be used to profile explicitly, although MyApp.pm still won't profile nor output anything by itself.

$c->stats_class

Returns or sets the stats (timing statistics) class. Catalyst::Stats is used by default.

$c->use_stats

Returns 1 when stats collection is enabled.

Note that this is a static method, not an accessor and should be overridden by declaring sub use_stats { 1 } in your MyApp.pm, not by calling $c->use_stats(1).

$c->write( $data )

Writes $data to the output stream. When using this method directly, you will need to manually set the Content-Length header to the length of your output data, if known.

version

Returns the Catalyst version number. Mostly useful for "powered by" messages in template systems.

CONFIGURATION

There are a number of 'base' config variables which can be set:

• default_model - The default model picked if you say $c->model. See "$c->model($name)".

• default_view - The default view to be rendered or returned when $c->view is called. See "$c->view($name)".

• disable_component_resolution_regex_fallback - Turns off the deprecated component resolution functionality so that if any of the component methods (e.g. $c->controller('Foo')) are called then regex search will not be attempted on string values and instead undef will be returned.

• home - The application home directory. In an uninstalled application, this is the top level application directory. In an installed application, this will be the directory containing MyApp.pm.

• ignore_frontend_proxy - See "PROXY SUPPORT"

• name - The name of the application in debug messages and the debug and welcome screens

• parse_on_demand - The request body (for example file uploads) will not be parsed until it is accessed. This allows you to (for example) check authentication (and reject the upload) before actually receiving all the data. See "ON-DEMAND PARSER"

• root - The root directory for templates. Usually this is just a subdirectory of the home directory, but you can set it to change the templates to a different directory.

• search_extra - Array reference passed to Module::Pluggable to for additional namespaces from which components will be loaded (and constructed and stored in $c->components).

• show_internal_actions - If true, causes internal actions such as _DISPATCH to be shown in hit debug tables in the test server.

• use_request_uri_for_path - Controls if the REQUEST_URI or PATH_INFO environment variable should be used for determining the request path.

  Most web server environments pass the requested path to the application using environment variables, from which Catalyst has to reconstruct the request base (i.e. the top level path to / in the application, exposed as $c->request->base) and the request path below that base.

  There are two methods of doing this, both of which have advantages and disadvantages. Which method is used is determined by the $c->config(use_request_uri_for_path) setting (which can either be true or false).

  use_request_uri_for_path => 0

  This is the default (and the) traditional method that Catalyst has used for determining the path information. The path is generated from a combination of the PATH_INFO and SCRIPT_NAME environment variables. The allows the application to behave correctly when mod_rewrite is being used to redirect requests into the application, as these variables are adjusted by mod_rewrite to take account for the redirect.

  However this method has the major disadvantage that it is impossible to correctly decode some elements of the path, as RFC 3875 says: "Unlike a URI path, the PATH_INFO is not URL-encoded, and cannot contain path-segment parameters." This means PATH_INFO is always decoded, and therefore Catalyst can't distinguish / vs %2F in paths (in addition to other encoded values).

  use_request_uri_for_path => 1

  This method uses the REQUEST_URI and SCRIPT_NAME environment variables. As REQUEST_URI is never decoded, this means that applications using this mode can correctly handle URIs including the %2F character (i.e. with AllowEncodedSlashes set to On in Apache).

  Given that this method of path resolution is provably more correct, it is recommended that you use this unless you have a specific need to deploy your application in a non-standard environment, and you are aware of the implications of not being able to handle encoded URI paths correctly.

  However it also means that in a number of cases when the app isn't installed directly at a path, but instead is having paths rewritten into it (e.g. as a .cgi/fcgi in a public_html directory, with mod_rewrite in a .htaccess file, or when SSI is used to rewrite pages into the app, or when sub-paths of the app are exposed at other URIs than that which the app is 'normally' based at with mod_rewrite), the resolution of $c->request->base will be incorrect.

• using_frontend_proxy - See "PROXY SUPPORT".

• encoding - See "ENCODING"

• abort_chain_on_error_fix

  When there is an error in an action chain, the default behavior is to continue processing the remaining actions and then catch the error upon chain end. This can lead to running actions when the application is in an unexpected state. If you have this issue, setting this config value to true will promptly exit a chain when there is an error raised in any action (thus terminating the chain early.)

  use like:

  __PACKAGE__->config(abort_chain_on_error_fix => 1);

  In the future this might become the default behavior.

• use_hash_multivalue_in_request

  In Catalyst::Request the methods query_parameters, body_parametes and parameters return a hashref where values might be scalar or an arrayref depending on the incoming data. In many cases this can be undesirable as it leads one to writing defensive code like the following:

  my ($val) = ref($c->req->parameters->{a}) ?
    @{$c->req->parameters->{a}} :
      $c->req->parameters->{a};

  Setting this configuration item to true will make Catalyst populate the attributes underlying these methods with an instance of Hash::MultiValue which is used by Plack::Request and others to solve this very issue. You may prefer this behavior to the default, if so enable this option (be warned if you enable it in a legacy application we are not sure if it is completely backwardly compatible).

• psgi_middleware - See "PSGI MIDDLEWARE".

• data_handlers - See "DATA HANDLERS".

EXCEPTIONS

Generally when you throw an exception inside an Action (or somewhere in your stack, such as in a model that an Action is calling) that exception is caught by Catalyst and unless you either catch it yourself (via eval or something like Try::Tiny or by reviewing the "error" stack, it will eventually reach "finalize_errors" and return either the debugging error stack page, or the default error page. However, if your exception can be caught by Plack::Middleware::HTTPExceptions, Catalyst will instead rethrow it so that it can be handled by that middleware (which is part of the default middleware). For example this would allow

use HTTP::Throwable::Factory 'http_throw';

sub throws_exception :Local {
  my ($self, $c) = @_;

  http_throw(SeeOther => { location => 
    $c->uri_for($self->action_for('redirect')) });

}

INTERNAL ACTIONS

Catalyst uses internal actions like _DISPATCH, _BEGIN, _AUTO, _ACTION, and _END. These are by default not shown in the private action table, but you can make them visible with a config parameter.

MyApp->config(show_internal_actions => 1);

ON-DEMAND PARSER

The request body is usually parsed at the beginning of a request, but if you want to handle input yourself, you can enable on-demand parsing with a config parameter.

MyApp->config(parse_on_demand => 1);

PROXY SUPPORT

Many production servers operate using the common double-server approach, with a lightweight frontend web server passing requests to a larger backend server. An application running on the backend server must deal with two problems: the remote user always appears to be 127.0.0.1 and the server's hostname will appear to be localhost regardless of the virtual host that the user connected through.

Catalyst will automatically detect this situation when you are running the frontend and backend servers on the same machine. The following changes are made to the request.

$c->req->address is set to the user's real IP address, as read from
the HTTP X-Forwarded-For header.

The host value for $c->req->base and $c->req->uri is set to the real
host, as read from the HTTP X-Forwarded-Host header.

Additionally, you may be running your backend application on an insecure connection (port 80) while your frontend proxy is running under SSL. If there is a discrepancy in the ports, use the HTTP header X-Forwarded-Port to tell Catalyst what port the frontend listens on. This will allow all URIs to be created properly.

In the case of passing in:

X-Forwarded-Port: 443

All calls to uri_for will result in an https link, as is expected.

Obviously, your web server must support these headers for this to work.

In a more complex server farm environment where you may have your frontend proxy server(s) on different machines, you will need to set a configuration option to tell Catalyst to read the proxied data from the headers.

MyApp->config(using_frontend_proxy => 1);

If you do not wish to use the proxy support at all, you may set:

MyApp->config(ignore_frontend_proxy => 0);

Note about psgi files

Note that if you supply your own .psgi file, calling MyApp->psgi_app(@_);, then this will not happen automatically.

You either need to apply Plack::Middleware::ReverseProxy yourself in your psgi, for example:

builder {
    enable "Plack::Middleware::ReverseProxy";
    MyApp->psgi_app
};

This will unconditionally add the ReverseProxy support, or you need to call $app = MyApp->apply_default_middlewares($app) (to conditionally apply the support depending upon your config).

See Catalyst::PSGI for more information.

THREAD SAFETY

Catalyst has been tested under Apache 2's threading mpm_worker, mpm_winnt, and the standalone forking HTTP server on Windows. We believe the Catalyst core to be thread-safe.

If you plan to operate in a threaded environment, remember that all other modules you are using must also be thread-safe. Some modules, most notably DBD::SQLite, are not thread-safe.

DATA HANDLERS

The Catalyst::Request object uses HTTP::Body to populate 'classic' HTML form parameters and URL search query fields. However it has become common for various alternative content types to be PUT or POSTed to your controllers and actions. People working on RESTful APIs, or using AJAX often use JSON, XML and other content types when communicating with an application server. In order to better support this use case, Catalyst defines a global configuration option, data_handlers, which lets you associate a content type with a coderef that parses that content type into something Perl can readily access.

   package MyApp::Web;

   use Catalyst;
   use JSON::Maybe;

   __PACKAGE__->config(
     data_handlers => {
       'application/json' => sub { local $/; decode_json $_->getline },
     },
     ## Any other configuration.
   );

   __PACKAGE__->setup;

By default Catalyst comes with a generic JSON data handler similar to the example given above, which uses JSON::Maybe to provide either JSON::PP (a pure Perl, dependency free JSON parser) or Cpanel::JSON::XS if you have it installed (if you want the faster XS parser, add it to you project Makefile.PL or dist.ini, cpanfile, etc.)

The data_handlers configuration is a hashref whose keys are HTTP Content-Types (matched against the incoming request type using a regexp such as to be case insensitive) and whose values are coderefs that receive a localized version of $_ which is a filehandle object pointing to received body.

This feature is considered an early access release and we reserve the right to alter the interface in order to provide a performant and secure solution to alternative request body content. Your reports welcomed!

PSGI MIDDLEWARE

You can define middleware, defined as Plack::Middleware or a compatible interface in configuration. Your middleware definitions are in the form of an arrayref under the configuration key psgi_middleware. Here's an example with details to follow:

   package MyApp::Web;

   use Catalyst;
   use Plack::Middleware::StackTrace;

   my $stacktrace_middleware = Plack::Middleware::StackTrace->new;

   __PACKAGE__->config(
     'psgi_middleware', [
       'Debug',
       '+MyApp::Custom',
       $stacktrace_middleware,
       'Session' => {store => 'File'},
       sub {
         my $app = shift;
         return sub {
           my $env = shift;
           $env->{myapp.customkey} = 'helloworld';
           $app->($env);
         },
       },
     ],
   );

   __PACKAGE__->setup;

So the general form is:

__PACKAGE__->config(psgi_middleware => \@middleware_definitions);

Where @middleware is one or more of the following, applied in the REVERSE of the order listed (to make it function similarly to Plack::Builder:

Alternatively, you may also define middleware by calling the "setup_middleware" package method:

package MyApp::Web;

use Catalyst;

__PACKAGE__->setup_middleware( \@middleware_definitions);
__PACKAGE__->setup;

In the case where you do both (use 'setup_middleware' and configuration) the package call to setup_middleware will be applied earlier (in other words its middleware will wrap closer to the application). Keep this in mind since in some cases the order of middleware is important.

The two approaches are not exclusive.

Middleware Object

An already initialized object that conforms to the Plack::Middleware specification:

   my $stacktrace_middleware = Plack::Middleware::StackTrace->new;

   __PACKAGE__->config(
     'psgi_middleware', [
       $stacktrace_middleware,
     ]);

coderef

A coderef that is an inlined middleware:

   __PACKAGE__->config(
     'psgi_middleware', [
       sub {
         my $app = shift;
         return sub {
           my $env = shift;
           if($env->{PATH_INFO} =~m/forced/) {
             Plack::App::File
               ->new(file=>TestApp->path_to(qw/share static forced.txt/))
               ->call($env);
           } else {
             return $app->($env);
           }
        },
     },
   ]);

a scalar

We assume the scalar refers to a namespace after normalizing it using the following rules:

(1) If the scalar is prefixed with a "+" (as in +MyApp::Foo) then the full string is assumed to be 'as is', and we just install and use the middleware.

(2) If the scalar begins with "Plack::Middleware" or your application namespace (the package name of your Catalyst application subclass), we also assume then that it is a full namespace, and use it.

(3) Lastly, we then assume that the scalar is a partial namespace, and attempt to resolve it first by looking for it under your application namespace (for example if you application is "MyApp::Web" and the scalar is "MyMiddleware", we'd look under "MyApp::Web::Middleware::MyMiddleware") and if we don't find it there, we will then look under the regular Plack::Middleware namespace (i.e. for the previous we'd try "Plack::Middleware::MyMiddleware"). We look under your application namespace first to let you 'override' common Plack::Middleware locally, should you find that a good idea.

Examples:

   package MyApp::Web;

   __PACKAGE__->config(
     'psgi_middleware', [
       'Debug',  ## MyAppWeb::Middleware::Debug->wrap or Plack::Middleware::Debug->wrap
       'Plack::Middleware::Stacktrace', ## Plack::Middleware::Stacktrace->wrap
       '+MyApp::Custom',  ## MyApp::Custom->wrap
     ],
   );

a scalar followed by a hashref

Just like the previous, except the following HashRef is used as arguments to initialize the middleware object.

__PACKAGE__->config(
  'psgi_middleware', [
     'Session' => {store => 'File'},
]);

Please see PSGI for more on middleware.

ENCODING

On request, decodes all params from encoding into a sequence of logical characters. On response, encodes body into encoding.

Methods

encoding

Returns an instance of an Encode encoding

print $c->encoding->name

handle_unicode_encoding_exception ($exception_context)

Method called when decoding process for a request fails.

An $exception_context hashref is provided to allow you to override the behaviour of your application when given data with incorrect encodings.

The default method throws exceptions in the case of invalid request parameters (resulting in a 500 error), but ignores errors in upload filenames.

The keys passed in the $exception_context hash are:

param_value

The value which was not able to be decoded.

error_msg

The exception received from Encode.

encoding_step

What type of data was being decoded. Valid values are (currently) params - for request parameters / arguments / captures and uploads - for request upload filenames.

SUPPORT

IRC:

Join #catalyst on irc.perl.org.

Mailing Lists:

http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst
http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst-dev

Web:

http://catalyst.perl.org

Wiki:

http://dev.catalyst.perl.org

SEE ALSO

Task::Catalyst - All you need to start with Catalyst

Catalyst::Manual - The Catalyst Manual

Catalyst::Component, Catalyst::Controller - Base classes for components

Catalyst::Engine - Core engine

Catalyst::Log - Log class.

Catalyst::Request - Request object

Catalyst::Response - Response object

Catalyst::Test - The test suite.

PROJECT FOUNDER

sri: Sebastian Riedel <sri@cpan.org>

CONTRIBUTORS

abw: Andy Wardley

acme: Leon Brocard <leon@astray.com>

abraxxa: Alexander Hartmaier <abraxxa@cpan.org>

Andrew Bramble

Andrew Ford <A.Ford@ford-mason.co.uk>

Andrew Ruthven

andyg: Andy Grundman <andy@hybridized.org>

audreyt: Audrey Tang

bricas: Brian Cassidy <bricas@cpan.org>

Caelum: Rafael Kitover <rkitover@io.com>

chansen: Christian Hansen

chicks: Christopher Hicks

Chisel Wright pause@herlpacker.co.uk

Danijel Milicevic me@danijel.de

David Kamholz <dkamholz@cpan.org>

David Naughton, naughton@umn.edu

David E. Wheeler

dhoss: Devin Austin <dhoss@cpan.org>

dkubb: Dan Kubb <dan.kubb-cpan@onautopilot.com>

Drew Taylor

dwc: Daniel Westermann-Clark <danieltwc@cpan.org>

esskar: Sascha Kiefer

fireartist: Carl Franks <cfranks@cpan.org>

frew: Arthur Axel "fREW" Schmidt <frioux@gmail.com>

gabb: Danijel Milicevic

Gary Ashton Jones

Gavin Henry ghenry@perl.me.uk

Geoff Richards

groditi: Guillermo Roditi <groditi@gmail.com>

hobbs: Andrew Rodland <andrew@cleverdomain.org>

ilmari: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

jcamacho: Juan Camacho

jester: Jesse Sheidlower jester@panix.com

jhannah: Jay Hannah <jay@jays.net>

Jody Belka

Johan Lindstrom

jon: Jon Schutz <jjschutz@cpan.org>

Jonathan Rockway <jrockway@cpan.org>

Kieren Diment kd@totaldatasolution.com

konobi: Scott McWhirter <konobi@cpan.org>

marcus: Marcus Ramberg <mramberg@cpan.org>

miyagawa: Tatsuhiko Miyagawa <miyagawa@bulknews.net>

mgrimes: Mark Grimes <mgrimes@cpan.org>

mst: Matt S. Trout <mst@shadowcatsystems.co.uk>

mugwump: Sam Vilain

naughton: David Naughton

ningu: David Kamholz <dkamholz@cpan.org>

nothingmuch: Yuval Kogman <nothingmuch@woobling.org>

numa: Dan Sully <daniel@cpan.org>

obra: Jesse Vincent

Octavian Rasnita

omega: Andreas Marienborg

Oleg Kostyuk <cub.uanic@gmail.com>

phaylon: Robert Sedlacek <phaylon@dunkelheit.at>

rafl: Florian Ragwitz <rafl@debian.org>

random: Roland Lammel <lammel@cpan.org>

Robert Sedlacek <rs@474.at>

SpiceMan: Marcel Montes

sky: Arthur Bergman

szbalint: Balint Szilakszi <szbalint@cpan.org>

t0m: Tomas Doran <bobtfish@bobtfish.net>

Ulf Edvinsson

vanstyn: Henry Van Styn <vanstyn@cpan.org>

Viljo Marrandi vilts@yahoo.com

Will Hawes info@whawes.co.uk

willert: Sebastian Willert <willert@cpan.org>

wreis: Wallace Reis <wreis@cpan.org>

Yuval Kogman, nothingmuch@woobling.org

rainboxx: Matthias Dietrich, perl@rainboxx.de

dd070: Dhaval Dhanani <dhaval070@gmail.com>

Upasana <me@upasana.me>

COPYRIGHT

Copyright (c) 2005-2014, the above named PROJECT FOUNDER and CONTRIBUTORS.

LICENSE

This library is free software. You can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Catalyst::Runtime

perl -MCPAN -e shell
install Catalyst::Runtime