NAME
CGI::Application::Plugin::Config::Context - Hierarchical, context-based
configuration support for CGI::Application
VERSION
Version 0.15
SYNOPSIS
Simple Access to Configuration
In your CGI::Application-based module:
use base 'CGI::Application';
use CGI::Application::Plugin::Config::Context;
sub cgiapp_init {
my $self = shift;
# Set config file and other options
$self->conf->init(
file => 'app.conf',
driver => 'ConfigGeneral',
);
}
sub my_run_mode {
my $self = shift;
# get entire configuration
my %conf = $self->conf->context;
# get entire configuration (as a reference)
my $conf = $self->conf->context;
# get single config parameter
my $value = $self->conf->param('some_value');
# get raw configuraion (pre-context-matching)
my $raw_config = $self->conf->raw;
my %raw_config = $self->conf->raw;
}
Configuration Based on URL or Module
You can match a configuration section to the request URL, or to the
module name. For instance, given the following configuration file:
admin_area = 0
<AppMatch ^MyApp::Admin>
admin_area = 1
title = Admin Area
</AppMatch>
<Location /cgi-bin/feedback.cgi>
title = Feedback Form
</Location>
The configuration will depend on how the script is called:
# URL: /cgi-bin/feedback.cgi?rm=add
# Module: MyApp::Feedback
print $self->conf->param('admin_area'); # 0
print $self->conf->param('title'); # 'Feedback Form'
# URL: /cgi-bin/admin/users.cgi
# Module: MyApp::Admin::Users
print $self->conf->param('admin_area'); # 1
print $self->conf->param('title'); # 'Admin Area'
Matching Configuration based on a Virtual Host
This module can also pick a configuration section based on the current
virtual-host:
# httpd.conf
<VirtualHost _default_:8080>
SetEnv SITE_NAME REDSITE
</VirtualHost>
# in app.conf
<Site BLUESITE>
background = blue
foreground = white
</Site>
<Site REDSITE>
background = red
foreground = pink
</Site>
<Site GREENSITE>
background = darkgreen
foreground = lightgreen
</Site>
Multiple configuration formats
Supports any configuration format supported by Config::Context. As of
this writing, that includes the following formats:
Apache-style syntax, via Config::General:
<AppMatch ^MyApp::Admin>
admin_area = 1
title = Admin Area
</AppMatch>
<Location /cgi-bin/feedback.cgi>
title = Feedback Form
</Location>
XML, via XML::Simple:
<AppMatch name="^MyApp::Admin">
<admin_area>1</admin_area>
<title>Admin Area</title>
</AppMatch>
<Location name="/cgi-bin/feedback.cgi">
<title>Feedback Form</title>
</Location>
Config::Scoped syntax:
AppMatch '^MyApp::Admin' {
admin_area = 1
title = Admin Area
}
Location '/cgi-bin/feedback.cgi' {
title = Feedback Form
}
Most of the examples in this document are in Config::General syntax, but
can be translated into the other formats fairly easily. For more
information, see the Config::Context docs.
DESCRIPTION
This module allows you to easily access configuration data stored in any
of the formats supported by Config::Context: Config::General (Apache
style), XML::Simple and Config::Scoped.
You can also automatically match configuration sections to the request
URL, or to the module name. This is similar to how Apache dynamically
selects a configuration by matching the request URL to (for instance)
"<Location>" and "<LocationMatch>" sections.
You can also select configuration sections based on Virtual Host or by
an environment variable you set in an ".htaccess" file. This allows you
to share a configuration file and an application between many virtual
hosts, each with its own unique configuration. This could be useful, for
instance, in providing multiple themes for a single application.
Simple access to Configuration
This module provides a "conf" method to your CGI::Application object.
First, you initialize the configuration system (typically in your
"cgiapp_init" method):
$self->conf->init(
file => 'app.conf',
driver => 'ConfigGeneral',
);
The configuration file is parsed at this point and the configuration is
available from this moment on.
Then, within your run-modes you can retrieve configuration data:
# get entire configuration
my %conf = $self->conf->context;
my $value = $conf{'some_value'};
# get entire configuration (as a reference)
my $conf = $self->conf->context;
my $value = $conf->{'some_value'};
# get single config parameter
my $value = $self->conf->param('some_value');
The "context" method provides the configuration based on the "context"
of your application, i.e. after matching configuration sections based on
runtime data such as the current URL or package name.
But you can also access the raw configuration data from before the
matching took place:
# get raw configuration
my %conf = $self->conf->raw;
# get raw configuration (as a reference)
my $conf = $self->conf->raw;
Multiple named Configurations
You can use more than one configuration by providing a name to the
"conf" method:
$self->conf('database')->init(
file => 'app.conf',
driver => 'ConfigGeneral',
);
$self->conf('application')->init(
file => 'app.conf',
driver => 'ConfigScoped',
);
...
my %db_config = $self->conf('database')->context;
my %app_config = $self->conf('application')->context;
Configuration based on URL or Module
Within your configuration file, you can provide different configurations
depending on the current URL, or on the package name of your
application.
<Site>
Matches against the "SITE_NAME" environment variable, using an
*exact* match.
# httpd.conf
<VirtualHost _default_:8080>
SetEnv SITE_NAME REDSITE
</VirtualHost>
# in app.conf
<Site BLUESITE>
background = blue
foreground = white
</Site>
<Site REDSITE>
background = red
foreground = pink
</Site>
<Site GREENSITE>
background = darkgreen
foreground = lightgreen
</Site>
You can name your sections something other than "<Site>", and you
can use a different environment variable than "SITE_NAME". See
"Notes on Site Matching", below.
<App>
Matches the Package name of your application module, for instance:
<App ABC_Books::Admin>
...
</App>
The match is performed hierarchically, like a filesystem path,
except using "::" as a delimiter, instead of "/". The match is tied
to the beginning of the package name, just like absolute paths. For
instance, given the section:
<App Site::Admin>
...
</App>
the packages "Site::Admin" and "Site::Admin::Users" would match, but
the packages "My::Site::Admin" and "Site::Administrative" would not.
<AppMatch>
Matches the package name of your application module, using a regular
expression. The expression is not tied to the start of the string.
For instance, given the section:
<AppMatch Site::Admin>
...
</AppMatch>
The following packages would all match: "Site::Admin",
"Site::Admin::Users", "My::Site::Admin", "MySite::Admin",
"Site::Administrative".
<Location>
Matches hierarchically against the request URI, including the path
and the "PATH_INFO" components, but *excluding* the scheme, host,
port and query string.
So, for instance with the following URL:
http://bookstore.example.com/cgi-bin/category.cgi/fiction/?rm=list
The Location would be:
/cgi-bin/category.cgi/fiction/
Internally, the location is obtained by calling the "url" method of
the query object (which is usually either a CGI or CGI::Simple
object):
$path = $webapp->query->url('-absolute' => 1, '-path_info' => 1);
<LocationMatch>
Matches against the request URI, using a regular expression.
Section Merge Order
The sections are matched in the following order:
Site: <Site>
Package Name: <App> and <AppMatch>
URL: <Location> and <LocationMatch>
When there is more than one matching section at the same level of
priority (e.g. two "<Location>" sections, or both an "<App>" and an
"<AppMatch>" section), then the sections are merged in the order of
shortest match first.
Values in sections matched later override the values in sections matched
earlier.
The idea is that the longer matches are more specific and should have
priority, and that URIs are more specific than Module names.
Section Nesting
The sections can be nested inside each other. For instance:
<Site BOOKSHOP>
<Location /admin>
admin_books = 1
</Location>
</Site>
<Location /admin>
<Site RECORDSHOP>
admin_records = 1
</Site>
</Location>
<App Bookshop::>
<App Admin::>
</App>
</App>
By default, the sections can be nested up to two levels deep. This alows
for "Location" sections within "Site" sections and *vice versa*. You can
change this by setting the nesting_depth parameter to init.
Note: there is limited support for this kind of nesting when using
Config::Scoped format files. See the documentation in
Config::Context::ConfigScoped for details.
Merging Configuration Values into your Template
You can easily pass values from your configuration files directly to
your templates. This allows you to associate HTML titles with URLs, or
keep text like copyright notices in your config file instead of your
templates:
copyright_notice = Copyright (C) 1492 Christopher Columbus
<Location /about>
title = "Manifest Destiny, Inc. - About Us"
</Location>
<Location /contact>
title = "Manifest Destiny, Inc. - Contact Us"
</Location>
If you use HTML::Template, you use the associate method when you load
the template:
$self->load_template(
'template.tmpl',
'associate' => $self->conf,
);
If you use Template::Toolkit (via the CGI::Application::Plugin::TT
module), you can accomplish the same thing by providing a custom
tt_pre_process method:
sub tt_pre_process {
my $self = shift;
my $template = shift;
my $template_params = shift;
my $config = $self->conf->context
foreach (keys %$config) {
unless (exists $template_params->{$_}) {
$template_params->{$_} = $config->{$_};
}
}
}
*NOTE: If you plan to merge data directly from your config files to
your* *templates, you should consider keeping your database passwords
and other* *sensitive data in a separate configuration file, in order to
avoid* *accidentally leaking these data into your web pages.*
METHODS
init
Initializes the plugin. The only required parameter is the source of the
configuration, either "file", "string" or "hash".
$self->conf->init(
file => 'app.conf',
);
The other paramters are described below:
file
The path to the configuration file to be parsed.
string
A string containing configuration data to be parsed.
hash
A Perl data structure containing containing the pre-parsed config
data.
driver
Which Config::Context driver should parse the config. Currently
supported drivers are:
driver module name
------ -----------
ConfigGeneral Config::Context::ConfigGeneral
ConfigScoped Config::Context::ConfigScoped
XMLSimple Config::Context::XMLSimple
The default driver is "ConfigGeneral".
driver_options
Options to pass directly on to the driver. This is a multi-level
hash, where the top level keys are the driver names:
my $conf = Config::Context->new(
driver => 'ConfigScoped',
driver_options => {
ConfigGeneral => {
-AutoLaunder => 1,
},
ConfigScoped = > {
warnings => {
permissions => 'off',
}
},
},
);
In this example the options under "ConfigScoped" will be passed to
the "ConfigScoped" driver. (The options under "ConfigGeneral" will
be ignored because "driver" is not set to 'ConfigGeneral'.)
cache_config_files
Whether or not to cache configuration files. Enabled, by default.
This option is useful in a persistent environment such as
"mod_perl". See "Config File Caching" under "ADVANCED USAGE", below.
stat_config
If config file caching is enabled, this option controls how often
the config files are checked to see if they have changed. The
default is 60 seconds. This option is useful in a persistent
environment such as "mod_perl". See "Config File Caching" under
"ADVANCED USAGE", below.
site_section_name
Change the name of the "<Site>" section to something else. For
instance, to use sections named "<VirtualHost>", use:
site_section_name => 'VirtualHost'
site_var
Change the name of the "SITE_NAME" environment variable used to
match against "<Site>" sections. For instance To change this name to
"HTTP_HOST", use:
site_var => 'HTTP_HOST',
nesting_depth
The number of levels deep that sections can be nested. The default
is two levels deep.
See "Section Nesting", above.
You can initialize the plugin from within your instance CGI script:
my $app = WebApp->new();
$app->conf->init(file => '../../config/app.conf');
$app->run();
Or you can do so from within your "cgiapp_init" method within the
application:
sub cgiapp_init {
my $self = shift;
$self->conf->init(
file => "$ENV{DOCUMENT_ROOT}/../config/app.conf"
);
}
context
Gets the entire configuration as a hash or hashref:
my %config = $self->conf->context; # as hash
my $config = $self->conf->context; # as hashref
raw
Gets the raw configuration as a hash or hashref:
my %raw_config = $self->conf->raw; # as hash
my $raw_config = $self->conf->raw; # as hashref
The raw configuration is the configuration before matching has taken
place. It includes all the raw config with all of the "<Location>",
"<App>", etc. sections intact.
param
Allows you to retrieve individual values from the configuration.
It behvaves like the "param" method in other classes, such as CGI,
CGI::Application and HTML::Template:
$value = $self->conf->param('some_key');
@all_keys = $self->conf->param();
get_current_context ($name)
This is a class method which returns the current configuration object.
my $conf = CGI::Application::Plugin::Config::Context->get_current_context;
print $conf->{'title'};
my %db_conf = CGI::Application::Plugin::Config::Context->get_current_context('db');
print $db_conf{'username'};
This method is most useful in situations where you don't have access to
the CGI::Application object, such within a Class::DBI class. See "Access
to Configuration information from another Class" for an example.
get_current_raw_config ($name)
Same as get_current_context, but returns the raw configuration.
ADVANCED USAGE
Usage in a Persistent Environment such as mod_perl
The following sections describe some notes about running this module
under mod_perl:
Config File Caching
Config::Context caches configuration files by default.
Each config file is read only once when the conf object is first
initialized. Thereafter, on each init, the cached config is used.
This means that in a persistent environment like mod_perl, the config
file is parsed on the first request, but not on subsequent requests.
If enough time has passed (sixty seconds by default) the config file is
checked to see if it has changed. If it has changed, then the file is
reread.
See the docs for Config::Context for details.
Notes on Site Matching
Renaming "<Site>" or "SITE_NAME"
Normally, the environment variable "SITE_NAME" is matched to "<Site>"
section.
You can change these with the site_section_name and site_var parameters
to init:
$self->conf->init(
file => 'app.conf',
site_section_name => 'Host',
site_var => 'MY_HOST',
);
This will match the environment variable "MY_HOST" to the "<Host>"
section.
Setting "SITE_NAME" from an ".htaccess" file or the CGI script
Since "SITE_NAME" is just an environment variable, you can set it
anywhere you can set environment variables. For instance in an
".htaccess" file:
# .htaccess
SetEnv SITE_NAME bookshop
Or even the calling CGI script:
#!/usr/bin/perl
use MySite::WebApp;
$ENV{'SITE_NAME'} = 'recordshop';
my $app = MySite::WebApp->new();
$app->run();
Access to Configuration information from another Class
You can also get at the current configuration settings from a completely
unrelated Perl module. This can be useful for instance if you need to
configure a set of Class::DBI classes, and you want them to be able to
pick up their configuration on their own. For instance:
# app.conf
<database>
connect_string = dbi:Pg:dbname=example
username = test
password = test
<options>
RaiseError = 1
AutoCommit = 1
</options>
</database>
# In your Class::DBI subclass
package My::Class::DBI::Base;
use base 'Class::DBI';
sub db_Main {
my $conf = CGI::Application::Plugin::Config::Context->get_current_context;
my $dsn = $conf->{'database'}{'connect_string'};
my $user = $conf->{'database'}{'username'};
my $pass = $conf->{'database'}{'password'};
my $opts = $conf->{'database'}{'options'};
return DBI->connect_cached($dsn, $user, $pass, $opts);
}
For this example to work, you need to make sure you call
"$self->conf->init" before you access the database through any of your
Class::DBI objects.
You can also call get_current_raw_config to get access to the raw
configuration.
Changing Parsing Behaviour Using Custom match_sections
Internally, this module uses Config::Context to parse its config files.
If you want to change the parsing behaviour, you can pass your own
match_sections list to init. For instance, if you want to allow only
sections named "<URL>", with no nesting, and have these matched exactly
to the complete request path, you could do the following:
# app.conf
admin_area = 0
user_area = 0
<URL /cgi-bin/admin.cgi>
admin_area = 1
</URL>
<URL /cgi-bin/user.cgi>
user_area = 1
</URL>
# in your cgiapp_init:
$self->conf->init(
file => 'app.conf',
nesting_depth => 1,
match_sections => [
{
name => 'URL',
match_type => 'exact',
merge_priority => 0,
section_type => 'path',
},
]
);
For reference, here is the default match_sections:
[
{
name => 'Site', # overridden by 'site_section_name'
match_type => 'exact',
merge_priority => 0,
section_type => 'env',
},
{
name => 'AppMatch',
match_type => 'regex',
section_type => 'module',
merge_priority => 1,
},
{
name => 'App',
match_type => 'path',
path_separator => '::',
section_type => 'module',
merge_priority => 1,
},
{
name => 'LocationMatch',
match_type => 'regex',
section_type => 'path',
merge_priority => 3,
},
{
name => 'Location',
match_type => 'path',
section_type => 'path',
merge_priority => 3,
},
],
For each section, the section_type param indicates what runtime variable
the section will be matched against. Here are the allowed values
env: matched to the environment variable SITE_NAME (overridden by site_name_var)
module: name of the Perl Module handling this request (e.g. MyApp::Users)
path: path of the request, including path_info (e.g. /cgi-bin/myapp/users.cgi/some/path)
You can use the above section_type values in your own custom
match_sections.
For more information on the syntax of match_sections, see the docs for
Config::Context.
Importing the 'conf' method, but using a different name.
If you want to access the features of this module using a method other
than "conf", you can do so via Anno Siegel's Exporter::Renaming module
(available on CPAN).
use Exporter::Renaming;
use CGI::Application::Plugin::Config::Context Renaming => [ conf => custom_config_method];
sub cgiapp_init {
my $self = shift;
# Set config file and other options
$self->custom_config_method->init(
file => 'app.conf',
driver => 'ConfigGeneral',
);
my $config = $self->custom_config_method->context;
# ....
}
AUTHOR
Michael Graham, "<mag-perl@occamstoothbrush.com>"
BUGS
Please report any bugs or feature requests to
"bug-cgi-application-plugin-config-general@rt.cpan.org", or through the
web interface at <http://rt.cpan.org>. I will be notified, and then
you'll automatically be notified of progress on your bug as I make
changes.
ACKNOWLEDGEMENTS
Thanks to the excellent examples provided by the other CGI::Application
plugin authors: Mark Stosberg, Michael Peters, Cees Hek and others.
SEE ALSO
CGI::Application
Config::Context
Config::Context::ConfigGeneral
Config::Context::ConfigScoped
Config::Context::XMLSimple
CGI::Application::Plugin::Config::Simple
CGI::Application::Plugin::ConfigAuto
Exporter::Renaming
CGI::Application::Plugin::TT
Template::Toolkit
HTML::Template
COPYRIGHT & LICENSE
Copyright 2005 Michael Graham, All Rights Reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.