NAME

Hook::Modular - making pluggable applications easy

SYNOPSIS

  # some_config.yaml

  global:
    log:
      level: error
    cache:
      base: /tmp/test-hook-modular
    # plugin_namespace: My::Test::Plugin
  
  plugins:
    - module: Some::Printer
      config:
        indent: 4
        indent_char: '*'
        text: 'this is some printer'


  # here is the plugin:

  package My::Test::Plugin::Some::Printer;
  use warnings;
  use strict;
  use base 'Hook::Modular::Plugin';
  
  sub register {
      my ($self, $context) = @_;
      $context->register_hook($self,
        'output.print' => $self->can('do_print'));
  }
  
  sub do_print { ... }


  # some_app.pl

  use base 'Hook::Modular';

  use constant PLUGIN_NAMESPACE => 'My::Test::Plugin';

  sub run {
    my $self = shift;
    $self->SUPER::run(@_);
    ...
    $self->run_hook('output.print', ...);
    ...
  }

  main->bootstrap(config => $config_filename);

DESCRIPTION

Hook::Modular makes writing pluggable applications easy. Use a config file to specify which plugins you want and to pass options to those plugins. The program to support those plugin then subclasses Hook::Modular and bootstraps itself. This causes the plugins to be loaded and registered. This gives each plugin the chance to register callbacks for any or all hooks the program offers. The program then runs the hooks in the order it desires. Each time a hook is run, all the callbacks the plugins have registered with this particular hook are run in order.

Hook::Modular does more than just load and call plugins, however. It also supports the following concepts:

Cache

Plugins can cache their settings. Cached items can also expire after a given time.

Crypt

Hook::Lexwrap can go over your config file and encrypt any passwords it finds (as determined by the key password). It will then rewrite the config file and make a backup of the original file. Encrypting and rewriting is turned off by default, but subclasses can enable it, or you can enable it from a config file itself.

At the moment, encrypting is rather basic: The passwords are only turned into base64.

Rules

Hook::Modular supports rule-based dispatch of plugins.

METHODS

new

  my $obj = Hook::Modular->new(config => $config_file_name);

Creates a new object and initializes it. The arguments are passed as a named hash. Valid argument keys:

config

Reads or sets the global configuration.

If the value is a simple string, it is interpreted as a filename. If the file is readable, it is loaded as YAML. If the filename is -, the configuration is read from STDIN.

If the value is a scalar reference, the dereferenced value is assumed to be YAML and is loaded.

If the value is a hash reference, the configuration is cloned from that hash reference.

The constructor also sets the application-wide configuration, which can be accessed using conf(), to the global part of the configuration data that has been passed to the constructor. This configuration is then augmented in various ways:

log level

  my $level = $self->conf->{log}{level}

The log level is set to debug, if it hasn't been set by the configuration data already.

In the config file, you can specify it this way:

  global:
    log:
      level: info

log encoding

  my $encoding = $self->conf->{log}{encoding}

The log encoding is set to the current terminal's encoding, if it hasn't been set by the configuration data already.

In the config file, you can specify it this way:

  global:
    log:
      level: info

plugin_namespace

  my $ns = $self->conf->{plugin_namespace};

The default plugin namespace is set to whatever the class defines as the PLUGIN_NAMESPACE constant, if the configuration data hasn't set it already. See the documentation of PLUGIN_NAMESPACE for details.

should_rewrite_config

  my $should_rewrite_config = $self->conf->{should_rewrite_config};

If the configuration data hasn't set it already to either 0 or 1, config file rewriting is turned off. See the documentation of SHOULD_REWRITE_CONFIG for details.

rule_namespaces

If the config file specifies any rule namespaces, they are added to the default rule namespaces. See the documentation of add_to_rule_namespaces() for details.

context, set_context

  my $context = $self->context;
  $self->set_context($context);

Gets and sets (respectively) the global context. It is singular; each program has only one context. Thie can be used to communicate between the plugins.

conf

  my %conf = $self->conf;
  my $plugin_path = $self->conf->{plugin_path} || [];
  $self->conf->{log}{level} = 'debug';

Returns a hash that has the application-wide configuration. It is set during new() from the global section of the configuration data and augmented with various other settings.

PLUGIN_NAMESPACE

  package My::TestApp;
  use base 'Hook::Modular';
  use constant PLUGIN_NAMESPACE => 'My::Test::Plugin';

A constant that specifies the namespace that is prepended to plugin names found in the configuration. Defaults to Hook::Modular::Plugin. Subclasses can and probably should override this value. For example, if the plugin namespace is set to My::Test::Plugin and the config file specifies a plugin with the name Some::Printer, we will try to load My:::Test::Plugin::Some::Printer.

In the config file, you can specify it this way:

  global:
    plugin_namespace: My::Test::Plugin

SHOULD_REWRITE_CONFIG

  package My::TestApp;
  use base 'Hook::Modular';
  use constant SHOULD_REWRITE_CONFIG => 1;

Hook::Modular can rewrite your config file, for example, to turn passwords into encrypted forms so they are not easily readable in the plain text. This behaviour is turned off by default, but the config file, or a subclass of Hook::Modular, can turn it on. In a config file, specify it this way:

In the config file, you can specify it this way:

  global:
    should_rewrite_config: 1

add_to_rule_namespace

  $self->add_to_rule_namespaces(
    qw/Some::Rule::Namespace Other::Rule::Namespace/);

Hook::Modular supports multiple rule namespace, that is, package prefixes that are used when looking for rule classes. The reason to allow multiple rule namespace is that Hook::Modular has some rules, and your subclass might well define its own rules, so Hook::Modular needs to know which package it might find rules in.

There is only one list of rule namespace per program. To add to rule namespaces in your program, don't access conf() directly, but use the proper class methods to do so: add_to_rule_namespaces() and rule_namespaces().

You can add to rule namespaces using the config file like this:

  global:
    rule_namespaces:
      - Some::Thing::Rule
      - Other::Thing::Rule

or, if you only want to add one rule namespace:

  global:
    rule_namespaces: Some::Thing::Rule

rule_namespaces

  my @ns = $self->rule_namespaces;

Returns the list of rule namespaces. See the documentation of add_to_rule_namespaces for details.

TAGS

If you talk about this module in blogs, on del.icio.us or anywhere else, please use the hookmodular tag.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests to bug-hook-modular@rt.cpan.org, or through the web interface at http://rt.cpan.org.

INSTALLATION

See perlmodinstall for information and options on installing Perl modules.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find a CPAN site near you. Or see <http://www.perl.com/CPAN/authors/id/M/MA/MARCEL/>.

AUTHOR

Marcel Grünauer, <marcel@cpan.org>

The code is almost completely lifted from Plagger, so really Tatsuhiko Miyagawa <miyagawa@bulknews.net> deserves all the credit.

COPYRIGHT AND LICENSE

Copyright 2007 by Marcel Grünauer

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