Provided by: libpoet-perl_0.16-1_all bug

NAME

       Poet::Manual::Intro - A gentle introduction to Poet

WHAT IS POET?

       Poet is a modern Perl web framework for Mason developers. It uses PSGI/Plack for server
       integration, Mason for request routing and templating, and a selection of best-of-breed
       CPAN modules for caching, logging and configuration.

INSTALLATION

       If you don't yet have cpanminus ("cpanm"), get it here
       <http://search.cpan.org/perldoc?App::cpanminus#INSTALLATION>. Then run

           cpanm -S --notest Poet

       Omit the "-S" if you don't have root, in which case cpanminus will install Poet and
       prereqs into "~/perl5".

       Omit the "--notest" if you want to run all the installation tests. Note that this will
       take about four times as long.

SETUP

       You should now have a "poet" app installed:

           % which poet
           /usr/local/bin/poet

       Run this to create your initial environment:

           % poet new MyApp
           my_app/.poet_root
           my_app/bin/app.psgi
           my_app/bin/get.pl
           ...
           Now run 'my_app/bin/run.pl' to start your server.

       The app name must be a valid Perl class name, generally either "CamelCase" ("MyApp") or an
       all-uppercase acronym ("TLA"). The directory, if not specified with -d, will be formed
       from the app name, but lowercased and underscored.

ENVIRONMENT

       In Poet, your entire web site lives within a single directory hierarchy called the
       environment. It contains subdirectories for configuration, libraries, Mason components
       (templates), static files, etc.

       Here are the subdirectories that are generated for you. If you don't need some of these
       directories, feel free to delete them. The only ones really required by Poet are "conf",
       "comps" and "lib".

       ·   "bin" - executable scripts

       ·   "comps" - Mason components (templates)

       ·   "conf" - configuration files

       ·   "data" - data not checked into version control, such as cache and object files

       ·   "db" - database related files such as your schema

       ·   "lib" - app-specific libraries and Poet subclasses

       ·   "logs" - logs from web server and from explicit logging statements

       ·   "static" - static web files - css, images, js

       ·   "t" - unit tests

   Initializing Poet
       Any web server or script must initialize Poet before it can use any of Poet's features.
       This is accomplished by with "Poet::Script":

           #!/usr/local/bin/perl
           use Poet::Script qw($conf $poet);

       You'll see this in "bin/run.pl", for example, the script you use to start your webserver.
       The "use Poet::Script" line does several things:

       ·   Searches upwards from the script for the environment root (as marked by the
           ".poet_root" file).

       ·   Reads and parses your configuration.

       ·   Unshifts onto @INC the lib/ subdirectory of your environment, so that you can "use"
           your application modules.

       ·   Imports the specified quick vars - in this case $conf and $poet - as well as some
           default utilities into the script namespace. More information about these below.

   Relocatable environments
       Ideally your environment will be relocatable -- if you move your environment to a
       different root, or checkout a second copy of it in a different root, things should just
       work.

       To achieve this you should never refer to exact environment directory paths in your code;
       instead you'll call Poet methods that return them. e.g. instead of this:

           system("/path/to/environment/bin/myscript.pl");

       you'll do this:

           system($poet->bin_path("myscript.pl"));

       (More information about this $poet variable below.)

   App name
       Your app name, e.g. "MyApp", is where you are expected to put app-specific subclasses. For
       example if you have a DBIx::Class schema, you'd create it under "MyApp::Schema" in the
       file "lib/MyApp/Schema.pm".

       The app name is also where Poet will look for subclasses of its own classes.

CONFIGURATION AND LAYERS

       Poet configuration files are kept in the "conf" subdirectory. The files are in YAML
       <http://www.yaml.org/> form and are merged in a particular order to create a single
       configuration hash. (If you want to use something other than YAML you can customize this.)

       Configuration files come in three varieties: "global", "layer", and "local", in order from
       least to highest precedence.

       Global
           Global configuration applies to all instances of your environment, and is typically
           checked into version control.

           Your generated environment includes a "conf/global.cfg".  This is simplest to start
           out with, but as a site scales in size and number of developers, you can split out
           your global configuration into multiple files in "conf/global/*.cfg".

       Layer
           Layers allow you to have different configuration for different contexts.  With all but
           the simplest site you'll have at least two layers: development (the internal
           environment where you develop) and production (the live site).  Later on, you might
           want a staging environment (which looks like production except for a different data
           source, etc.).

           In general you can have as many layers as you like.  Each layer has a corresponding
           configuration file in "conf/layer/*.cfg"; only one layer file will be loaded per
           environment. We recommend that these files all be checked into version control as
           well, so that changes to each layer are tracked.

           Note: layer is analagous to Plack's environment concept. And in fact, "bin/run.pl"
           passes the layer to plackup's <-E> option.

       Local
           "conf/local.cfg" contains configuration local to this specific environment instance.
           This is where the current layer must be defined. It is also the only configuration
           file that must exist, and the only one that should not be checked into version
           control.

           You can also specify an extra local file via $ENV{POET_EXTRA_CONF_FILE}.

       There are a variety of ways to access configuration:

           my $value = $conf->get('key', 'default');
           my $value = $conf->get_or_die('key');

           my $listref = $conf->get_list('key', ['default']);
           my $hashref = $conf->get_hash('key', {'default' => 5});
           my $bool = $conf->get_boolean('key');

       See below for more information about this $conf variable, and see Poet::Conf for more
       information on specifying and accessing configuration.

   Development versus live mode
       Although you may have as many layers as you like, Poet also maintains a more limited
       binary notion of development mode versus live mode. By default, you're in development mode
       iff layer equals 'development', and in live mode otherwise.

       You can use these boolean methods to determine which mode you're in at runtime:

           $conf->is_development
           $conf->is_live

       These are mutually exclusive (exactly one is always true).

       Poet uses development/live mode to determine things like

       ·   whether to turn on automatic server restarting

       ·   whether to display errors in the browser

       ·   whether to enable debugging utilities

       You can customize how mode is determined by subclassing Poet::Conf.

SERVER RUNNER AND MIDDLEWARE

       "poet new" generates "bin/run.pl" and "bin/app.psgi" for you.

       "bin/run.pl" is a wrapper around plackup, which starts your server.  It has a few sensible
       defaults, such as setting up autorestart in development mode and using an access log in
       live mode. It will also take a few options from configuration, e.g.

           server:
              host: 127.0.0.1
              port: 5000

       If you are using something other than plackup (e.g.  Server::Starter) then you'll have to
       adapt this into your own startup script.

       "bin/app.psgi" defines your PSGI app. It's the place to add Plack middleware, or change
       the configuration of the default middleware. For example, to enable basic authentication
       with an "conf/.htpasswd" file, add this to app.psgi:

           enable "Auth::Htpasswd", file => $poet->conf_path('.htpasswd');

QUICK VARS AND UTILITIES

       Poet makes it easy to import certain variables (known as "quick vars") and utility sets
       into any module or script in your environment. You've seen two examples of quick vars
       above: $conf, the global configuration variable, and $poet, the global environment object.

       In a script, this looks like:

           #!/usr/local/bin/perl
           use Poet::Script qw($conf :file);

       In a module, this looks like:

           package MyApp::Foo;
           use Poet qw($cache $poet);

       And every Mason component automatically gets this on top:

           use Poet qw($conf $poet :web);

       Debug utilities are automatically imported without having to specify a tag.

       See Poet::Import for a complete list of quick vars and utility sets.

HANDLING HTTP REQUESTS

       HTTP requests are handled with PSGI/Plack and Mason.

       A persistent Mason interpreter is created at server startup, with component root set to
       the "comps" subdirectory. (See Poet::Mason for other default settings and how to configure
       them.)

       When an HTTP request comes in, Poet

       ·   Constructs a Poet::Plack::Request object from the plack environment.  This is a thin
           subclass of Plack::Request and provides information such as the URL and incoming HTTP
           headers. It is made available in Mason components as "$m->req".

       ·   Constructs an empty Poet::Plack::Response object. This is a thin subclass of
           Plack::Response, and you may use it to set things such as the HTTP status and headers.
           It is made available in Mason components as "$m->res".

       ·   Calls "$interp->run" with the URL and the GET/POST parameters. So for example, a URL
           like

               /foo/bar?a=5&b=6

           would result in

               $interp->run("/foo/bar", a=>5, b=>6);

           From there Mason will choose a component to dispatch to - see
           Mason::Manual::RequestDispatch and Mason::Plugin::RouterSimple.

   Generating content with Mason
       Mason is a full-featured templating system and beyond our ability to summarize here.
       Recommended reading:

       ·   Poet::Manual::Tutorial, especially starting here

       ·   Mason::Manual::Components

       ·   Mason::Manual::Syntax

   Success and failure results
       If the Mason request finishes successfully, the Mason output becomes the plack response
       body, the status code is set to 200 if it hasn't already been set, and the content type is
       set to "text/html" (or the specified default content type) if it hasn't already been set.

       If the top-level component path cannot be found, the status code is set to 404.

       If any other kind of runtime error occurs in development mode, it will be nicely displayed
       in the browser via StackTrace middleware. Outside of development it will be logged and
       sent as a 500 error response.

       You can call "$m->redirect" and "$m->not_found" to generate redirect and not_found results
       from a component. These are documented in Poet::Mason.

   Multiple values for parameters
       If there are multiple values for a GET or POST parameter, generally only the last value
       will be kept, as per Hash::MultiValue. However, if the corresponding attribute in the page
       component is declared an "ArrayRef", then all values will be kept and passed in as an
       arrayref. For example, if the page component "/foo/bar.mc" has these declarations:

           <%class>
           has 'a';
           has 'b' => (isa => "Int");
           has 'c' => (isa => "ArrayRef");
           has 'd' => (isa => "ArrayRef[Int]");
           </%class>

       then this URL

           /foo/bar?a=1&a=2&b=3&b=4&c=5&c=6&d=7&d=8

       would result in

           $interp->run("/foo/bar", a=>2, b=>4, c=>[5,6], d => [7,8]);

       You can always get the original Hash::MultiValue object from "$m->request_args". e.g.

           my $hmv = $m->request_args;
           # get all values for 'e'
           $hmv->get_all('e');

LOGGING

       Poet uses the Log::Log4perl engine for logging, but with a much simpler configuration for
       the common cases. (If you want to use something other than Log4perl you can customize
       this.)

       Once you have a $log variable, logging looks like:

           $log->error("an error occurred");

           $log->debugf("arguments are: %s", \@_)
               if $log->is_debug();

       By default, all logs go to "logs/poet.log" with a reasonable set of metadata such as
       timestamp.

       See Poet::Log for more information.

CACHING

       Poet uses CHI for caching, providing access to a wide variety of cache backends (memory,
       files, memcached, etc.) You can configure caching differently for different namespaces.

       Once you have a $cache variable, caching looks like:

           my $customer = $cache->get($name);
           if ( !defined $customer ) {
               $customer = get_customer_from_db($name);
               $cache->set( $name, $customer, "10 minutes" );
           }

       or

           my $customer2 = $cache->compute($name2, "10 minutes", sub {
               get_customer_from_db($name2)
           });

       By default, everything is cached in files under "data/chi".

       See Poet::Cache for more information.

SEE ALSO

       Poet

AUTHOR

       Jonathan Swartz <swartz@pobox.com>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2012 by Jonathan Swartz.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.