Mark Stosberg

Last updated: Sat Feb 18 23:42:29 EST 2006

NAME

CGI::Application::Standard::Config -- Define a standard configuration API for CGI::Application

RATIONALE

This module defines a minimum standard interface that configuration plugins for CGI::Application should meet. Having such a standard allows other plugin authors to rely on basic configuration functionality without coding exceptions for several configuration modules, or giving up on such integration.

SYNOPSIS

For Average Users

Simply load the config plugin before other modules that might use it:

  use CGI::Application::Plugin::ConfigAuto;
  use CGI::Application::Plugin::Session;

For Configuration plugin authors

Configuration plugin authors only need to follow the standards documented below.

For other plugin authors who wish to rely on the standard

Plugin authors who want to possibly use this standard can do so by simply using this module:

  package CGI::Application::Plugin::Session;
  use CGI::Application::Standard::Config;

If a standards complaint config module hasn't already been loaded a stub for config() will be added which will safely return undef.

Example use by another plugin

Here code first tries to get configuration details first from a config file, then from options passed to a plugin-specific config method, and finally applies defaults if no configuration options are found.

 my $session_options = $self->config('Session_options')
                                      || $self->session_config()
                                      || $self->session_defaults;

Standard Interface Definition

The following defines a minimum standard for configuration plugins to meet.

Config plugins are free to provide to additional functionality.

Configuration plugins are also encourage to explicity document that they are using CGI::Application::Standard::Config.

If there are existing methods that follow the standard but have different names, you can use this example to always export your method:

  sub import {
    my $app = caller;
    no strict 'refs';
    my $full_name = $app . '::config';
    # Change cfg to your config()-compliant method name
    *$full_name = \&cfg;
    CGI::Application::Plugin::YourNameHere->export_to_level(1,@_);
  }

$self->std_config

This method should be exported by default to simply declare that you meet the standard report which version of the standard you meet. This simple implementation is recommended:

 sub std_config { return 1; }

$self->config

The intended use is to load to read-only configuration details once from a config file at start up time.

This service is provided by plugins (list below). They must support at at least this syntax:

 my $value = $self->config('key');

By default, config() simply returns undef, making it safe for other plugins to directly to check if $self-config('key')> returns the value it needs.

config() must be exported by default.

For applications that need little configuration, config() is not necessary-- using PARAMS in an instance script should suffice.

Also, the param() is the appropriate method to use to set a configuration value at run time.

Configuration plugins that provide at least this basic API include:

CGI::Application::Plugin::ConfigAuto.

Standard config variables

Users are encouraged to use these standard config variable names, to ease compatibility between plugins:

 ROOT_URI - A URI corresponding to the project root (http://foo.com/proj )
 ROOT_DIR - a file system path to the same location ( /home/joe/www/proj )

All-caps are used to denote that config variables are essentially global constants.

Why URI and not URL? The wikipedia explains:

  The contemporary point of view among the working group that oversees URIs is
  that the terms URL and URN are context-dependent aspects of URI and rarely
  need to be distinguished. Furthermore, the term URL is increasingly becoming
  obsolete, as it is rarely necessary to differentiate between URLs and URIs,
  in general. 

Standard Version

This is 1.0 of the CGI::Application config() standard.

AUTHOR

Written by Mark Stosberg <mark@summersault.com> with input from the CGI::Application community.

COPYRIGHT and LICENSE

Copyright (C) 2008, Mark Stosberg. All rights reserved.

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




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