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#============================================================= -*-Perl-*-
#
# Template::Plugins
#
# DESCRIPTION
# Plugin provider which handles the loading of plugin modules and
# instantiation of plugin objects.
#
# AUTHORS
# Andy Wardley <abw@wardley.org>
#
# COPYRIGHT
# Copyright (C) 1996-2006 Andy Wardley. All Rights Reserved.
# Copyright (C) 1998-2000 Canon Research Centre Europe Ltd.
#
# This module is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# REVISION
# $Id$
#
#============================================================================
package Template::Plugins;
use strict;
use warnings;
use base 'Template::Base';
use Template::Constants;
our $VERSION = '3.100';
our $DEBUG = 0 unless defined $DEBUG;
our $PLUGIN_BASE = 'Template::Plugin';
our $STD_PLUGINS = {
'assert' => 'Template::Plugin::Assert',
'cgi' => 'Template::Plugin::CGI',
'datafile' => 'Template::Plugin::Datafile',
'date' => 'Template::Plugin::Date',
'debug' => 'Template::Plugin::Debug',
'directory' => 'Template::Plugin::Directory',
'dbi' => 'Template::Plugin::DBI',
'dumper' => 'Template::Plugin::Dumper',
'file' => 'Template::Plugin::File',
'format' => 'Template::Plugin::Format',
'html' => 'Template::Plugin::HTML',
'image' => 'Template::Plugin::Image',
'iterator' => 'Template::Plugin::Iterator',
'latex' => 'Template::Plugin::Latex',
'pod' => 'Template::Plugin::Pod',
'scalar' => 'Template::Plugin::Scalar',
'table' => 'Template::Plugin::Table',
'url' => 'Template::Plugin::URL',
'view' => 'Template::Plugin::View',
'wrap' => 'Template::Plugin::Wrap',
'xml' => 'Template::Plugin::XML',
'xmlstyle' => 'Template::Plugin::XML::Style',
};
#========================================================================
# -- PUBLIC METHODS --
#========================================================================
#------------------------------------------------------------------------
# fetch($name, \@args, $context)
#
# General purpose method for requesting instantiation of a plugin
# object. The name of the plugin is passed as the first parameter.
# The internal FACTORY lookup table is consulted to retrieve the
# appropriate factory object or class name. If undefined, the _load()
# method is called to attempt to load the module and return a factory
# class/object which is then cached for subsequent use. A reference
# to the calling context should be passed as the third parameter.
# This is passed to the _load() class method. The new() method is
# then called against the factory class name or prototype object to
# instantiate a new plugin object, passing any arguments specified by
# list reference as the second parameter. e.g. where $factory is the
# class name 'MyClass', the new() method is called as a class method,
# $factory->new(...), equivalent to MyClass->new(...) . Where
# $factory is a prototype object, the new() method is called as an
# object method, $myobject->new(...). This latter approach allows
# plugins to act as Singletons, cache shared data, etc.
#
# Returns a reference to a plugin, (undef, STATUS_DECLINE) to decline
# the request or ($error, STATUS_ERROR) on error.
#------------------------------------------------------------------------
sub fetch {
my ($self, $name, $args, $context) = @_;
my ($factory, $plugin, $error);
$self->debug("fetch($name, ",
defined $args ? ('[ ', join(', ', @$args), ' ]') : '<no args>', ', ',
defined $context ? $context : '<no context>',
')') if $self->{ DEBUG };
# NOTE:
# the $context ref gets passed as the first parameter to all regular
# plugins, but not to those loaded via LOAD_PERL; to hack around
# this until we have a better implementation, we pass the $args
# reference to _load() and let it unshift the first args in the
# LOAD_PERL case
$args ||= [ ];
unshift @$args, $context;
$factory = $self->{ FACTORY }->{ $name } ||= do {
($factory, $error) = $self->_load($name, $context);
return ($factory, $error) if $error; ## RETURN
$factory;
};
# call the new() method on the factory object or class name
eval {
if (ref $factory eq 'CODE') {
defined( $plugin = &$factory(@$args) )
|| die "$name plugin failed\n";
}
else {
defined( $plugin = $factory->new(@$args) )
|| die "$name plugin failed: ", $factory->error(), "\n";
}
};
if ($error = $@) {
# chomp $error;
return $self->{ TOLERANT }
? (undef, Template::Constants::STATUS_DECLINED)
: ($error, Template::Constants::STATUS_ERROR);
}
return $plugin;
}
#========================================================================
# -- PRIVATE METHODS --
#========================================================================
#------------------------------------------------------------------------
# _init(\%config)
#
# Private initialisation method.
#------------------------------------------------------------------------
sub _init {
my ($self, $params) = @_;
my ($pbase, $plugins, $factory) =
@$params{ qw( PLUGIN_BASE PLUGINS PLUGIN_FACTORY ) };
$plugins ||= { };
# update PLUGIN_BASE to an array ref if necessary
$pbase = [ ] unless defined $pbase;
$pbase = [ $pbase ] unless ref($pbase) eq 'ARRAY';
# add default plugin base (Template::Plugin) if set
push(@$pbase, $PLUGIN_BASE) if $PLUGIN_BASE;
$self->{ PLUGIN_BASE } = $pbase;
$self->{ PLUGINS } = { %$STD_PLUGINS, %$plugins };
$self->{ TOLERANT } = $params->{ TOLERANT } || 0;
$self->{ LOAD_PERL } = $params->{ LOAD_PERL } || 0;
$self->{ FACTORY } = $factory || { };
$self->{ DEBUG } = ( $params->{ DEBUG } || 0 )
& Template::Constants::DEBUG_PLUGINS;
return $self;
}
#------------------------------------------------------------------------
# _load($name, $context)
#
# Private method which attempts to load a plugin module and determine the
# correct factory name or object by calling the load() class method in
# the loaded module.
#------------------------------------------------------------------------
sub _load {
my ($self, $name, $context) = @_;
my ($factory, $module, $base, $pkg, $file, $ok, $error);
if ($module = $self->{ PLUGINS }->{ $name } || $self->{ PLUGINS }->{ lc $name }) {
# plugin module name is explicitly stated in PLUGIN_NAME
$pkg = $module;
($file = $module) =~ s|::|/|g;
$file =~ s|::|/|g;
$self->debug("loading $module.pm (PLUGIN_NAME)")
if $self->{ DEBUG };
$ok = eval { require "$file.pm" };
$error = $@;
}
else {
# try each of the PLUGIN_BASE values to build module name
($module = $name) =~ s/\./::/g;
foreach $base (@{ $self->{ PLUGIN_BASE } }) {
$pkg = $base . '::' . $module;
($file = $pkg) =~ s|::|/|g;
$self->debug("loading $file.pm (PLUGIN_BASE)")
if $self->{ DEBUG };
$ok = eval { require "$file.pm" };
last unless $@;
$error .= "$@\n"
unless ($@ =~ /^Can\'t locate $file\.pm/);
}
}
if ($ok) {
$self->debug("calling $pkg->load()") if $self->{ DEBUG };
$factory = eval { $pkg->load($context) };
$error = '';
if ($@ || ! $factory) {
$error = $@ || 'load() returned a false value';
}
}
elsif ($self->{ LOAD_PERL }) {
# fallback - is it a regular Perl module?
($file = $module) =~ s|::|/|g;
eval { require "$file.pm" };
if ($@) {
$error = $@;
}
else {
# this is a regular Perl module so the new() constructor
# isn't expecting a $context reference as the first argument;
# so we construct a closure which removes it before calling
# $module->new(@_);
$factory = sub {
shift;
$module->new(@_);
};
$error = '';
}
}
if ($factory) {
$self->debug("$name => $factory") if $self->{ DEBUG };
return $factory;
}
elsif ($error) {
return $self->{ TOLERANT }
? (undef, Template::Constants::STATUS_DECLINED)
: ($error, Template::Constants::STATUS_ERROR);
}
else {
return (undef, Template::Constants::STATUS_DECLINED);
}
}
1;
__END__
=head1 NAME
Template::Plugins - Plugin provider module
=head1 SYNOPSIS
use Template::Plugins;
$plugin_provider = Template::Plugins->new(\%options);
($plugin, $error) = $plugin_provider->fetch($name, @args);
=head1 DESCRIPTION
The C<Template::Plugins> module defines a provider class which can be used
to load and instantiate Template Toolkit plugin modules.
=head1 METHODS
=head2 new(\%params)
Constructor method which instantiates and returns a reference to a
C<Template::Plugins> object. A reference to a hash array of configuration
items may be passed as a parameter. These are described below.
Note that the L<Template> front-end module creates a C<Template::Plugins>
provider, passing all configuration items. Thus, the examples shown
below in the form:
$plugprov = Template::Plugins->new({
PLUGIN_BASE => 'MyTemplate::Plugin',
LOAD_PERL => 1,
...
});
can also be used via the L<Template> module as:
$ttengine = Template->new({
PLUGIN_BASE => 'MyTemplate::Plugin',
LOAD_PERL => 1,
...
});
as well as the more explicit form of:
$plugprov = Template::Plugins->new({
PLUGIN_BASE => 'MyTemplate::Plugin',
LOAD_PERL => 1,
...
});
$ttengine = Template->new({
LOAD_PLUGINS => [ $plugprov ],
});
=head2 fetch($name, @args)
Called to request that a plugin of a given name be provided. The relevant
module is first loaded (if necessary) and the
L<load()|Template::Plugin#load()> class method called to return the factory
class name (usually the same package name) or a factory object (a prototype).
The L<new()|Template::Plugin#new()> method is then called as a class or object
method against the factory, passing all remaining parameters.
Returns a reference to a new plugin object or C<($error, STATUS_ERROR)>
on error. May also return C<(undef, STATUS_DECLINED)> to decline to
serve the request. If C<TOLERANT> is set then all errors will be
returned as declines.
=head1 CONFIGURATION OPTIONS
The following list summarises the configuration options that can be provided
to the C<Template::Plugins> L<new()> constructor. Please consult
L<Template::Manual::Config> for further details and examples of each
configuration option in use.
=head2 PLUGINS
The L<PLUGINS|Template::Manual::Config#PLUGINS> option can be used to provide
a reference to a hash array that maps plugin names to Perl module names.
my $plugins = Template::Plugins->new({
PLUGINS => {
cgi => 'MyOrg::Template::Plugin::CGI',
foo => 'MyOrg::Template::Plugin::Foo',
bar => 'MyOrg::Template::Plugin::Bar',
},
});
=head2 PLUGIN_BASE
If a plugin is not defined in the L<PLUGINS|Template::Manual::Config#PLUGINS>
hash then the L<PLUGIN_BASE|Template::Manual::Config#PLUGIN_BASE> is used to
attempt to construct a correct Perl module name which can be successfully
loaded.
# single value PLUGIN_BASE
my $plugins = Template::Plugins->new({
PLUGIN_BASE => 'MyOrg::Template::Plugin',
});
# multiple value PLUGIN_BASE
my $plugins = Template::Plugins->new({
PLUGIN_BASE => [ 'MyOrg::Template::Plugin',
'YourOrg::Template::Plugin' ],
});
=head2 LOAD_PERL
The L<LOAD_PERL|Template::Manual::Config#LOAD_PERL> option can be set to allow
you to load regular Perl modules (i.e. those that don't reside in the
C<Template::Plugin> or another user-defined namespace) as plugins.
If a plugin cannot be loaded using the
L<PLUGINS|Template::Manual::Config#PLUGINS> or
L<PLUGIN_BASE|Template::Manual::Config#PLUGIN_BASE> approaches then,
if the L<LOAD_PERL|Template::Manual::Config#LOAD_PERL> is set, the
provider will make a final attempt to load the module without prepending any
prefix to the module path.
Unlike regular plugins, modules loaded using L<LOAD_PERL|Template::Manual::Config#LOAD_PERL>
do not receive a L<Template::Context> reference as the first argument to the
C<new()> constructor method.
=head2 TOLERANT
The L<TOLERANT|Template::Manual::Config#TOLERANT> flag can be set to indicate
that the C<Template::Plugins> module should ignore any errors encountered while
loading a plugin and instead return C<STATUS_DECLINED>.
=head2 DEBUG
The L<DEBUG|Template::Manual::Config#DEBUG> option can be used to enable
debugging messages for the C<Template::Plugins> module by setting it to
include the C<DEBUG_PLUGINS> value.
use Template::Constants qw( :debug );
my $template = Template->new({
DEBUG => DEBUG_FILTERS | DEBUG_PLUGINS,
});
=head1 TEMPLATE TOOLKIT PLUGINS
Please see L<Template::Manual::Plugins> For a complete list of all the plugin
modules distributed with the Template Toolkit.
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 1996-2007 Andy Wardley. All Rights Reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<Template::Manual::Plugins>, L<Template::Plugin>, L<Template::Context>, L<Template>.
=cut
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