Template::Service(3)

NAME
Template::Service - General purpose template processing service

SYNOPSIS
    use Template::Service;

    my $service = Template::Service->new({
        PRE_PROCESS  => [ 'config', 'header' ],
        POST_PROCESS => 'footer',
        ERROR        => {
            user     => 'user/index.html',
            dbi      => 'error/database',
            default  => 'error/default',
        },
    });

    my $output = $service->process($template_name, \%replace)
        || die $service->error(), "\n";

DESCRIPTION
The Template::Service module implements an object class for providing a consistent template processing service.

Standard header (PRE_PROCESS) and footer (POST_PROCESS) templates may be specified which are prepended and appended to all templates processed by the service (but not any other templates or blocks INCLUDEd or PROCESSed from within). An ERROR hash may be specified which redirects the service to an alternate template file in the case of uncaught exceptions being thrown. This allows errors to be automatically handled by the service and a guaranteed valid response to be generated regardless of any processing problems encountered.

A default Template::Service object is created by the Template module. Any Template::Service options may be passed to the Template new() constructor method and will be forwarded to the Template::Service constructor.

    use Template;

    my $template = Template->new({
        PRE_PROCESS  => 'header',
        POST_PROCESS => 'footer',
    });

Similarly, the Template::Service constructor will forward all configuration parameters onto other default objects (e.g. Template::Context) that it may need to instantiate.

A Template::Service object (or subclass/derivative) can be explicitly instantiated and passed to the Template new() constructor method as the SERVICE item.

    use Template;
    use Template::Service;

    my $service = Template::Service->new({
        PRE_PROCESS  => 'header',
        POST_PROCESS => 'footer',
    });

    my $template = Template->new({
        SERVICE => $service,
    });

The Template::Service module can be sub-classed to create custom service handlers.

    use Template;
    use MyOrg::Template::Service;

    my $service = MyOrg::Template::Service->new({
        PRE_PROCESS  => 'header',
        POST_PROCESS => 'footer',
        COOL_OPTION  => 'enabled in spades',
    });

    my $template = Template->new({
        SERVICE => $service,
    });

The Template module uses the Template::Config service() factory method to create a default service object when required. The $Template::Config::SERVICE package variable may be set to specify an alternate service module. This will be loaded automatically and its new() constructor method called by the service() factory method when a default service object is required. Thus the previous example could be written as:

    use Template;

    $Template::Config::SERVICE = 'MyOrg::Template::Service';

    my $template = Template->new({
        PRE_PROCESS  => 'header',
        POST_PROCESS => 'footer',
        COOL_OPTION  => 'enabled in spades',
    });

METHODS

  new(\%config)
The new() constructor method is called to instantiate a Template::Service object. Configuration parameters may be specified as a HASH reference or as a list of (name => value) pairs.

    my $service1 = Template::Service->new({
        PRE_PROCESS  => 'header',
        POST_PROCESS => 'footer',
    });

    my $service2 = Template::Service->new( ERROR => 'error.html' );

The new() method returns a Template::Service object (or sub-class) or undef on error. In the latter case, a relevant error message can be retrieved by the error() class method or directly from the $Template::Service::ERROR package variable.

    my $service = Template::Service->new(\%config)
        || die Template::Service->error();

    my $service = Template::Service->new(\%config)
        || die $Template::Service::ERROR;

The following configuration items may be specified:

PRE_PROCESS, POST_PROCESS
    These values may be set to contain the name(s) of template files (relative to INCLUDE_PATH) which should be processed immediately before and/or after each template. These do not get added to templates processed into a document via directives such as INCLUDE, PROCESS, WRAPPER etc.

        my $service = Template::Service->new({
            PRE_PROCESS  => 'header',
            POST_PROCESS => 'footer',
        };

    Multiple templates may be specified as a reference to a list. Each is processed in the order defined.

        my $service = Template::Service->new({
            PRE_PROCESS  => [ 'config', 'header' ],
            POST_PROCESS => 'footer',
        };

    Alternately, multiple template may be specified as a single string, delimited by ':'. This delimiter string can be changed via the DELIMITER option.

        my $service = Template::Service->new({
            PRE_PROCESS  => 'config:header',
            POST_PROCESS => 'footer',
        };

    The PRE_PROCESS and POST_PROCESS templates are evaluated in the same variable context as the main document and may define or update variables for subsequent use.

    config:

        [% # set some site-wide variables
           bgcolor = '#ffffff'
           version = 2.718
        %]

    header:

        [% DEFAULT title = 'My Funky Web Site' %]
        <html>
        <head>
        <title>[% title %]</title>
        </head>
        <body bgcolor="[% bgcolor %]">

    footer:

        <hr>
        Version [% version %]
        </body>
        </html>

    The Template::Document object representing the main template being processed is available within PRE_PROCESS and POST_PROCESS templates as the 'template' variable. Metadata items defined via the META directive may be accessed accordingly.

        $service->process('mydoc.html', $vars);

    mydoc.html:

        [% META title = 'My Document Title' %]
        blah blah blah
        ...

    header:

        <html>
        <head>
        <title>[% template.title %]</title></head>
        <body bgcolor="[% bgcolor %]">

PROCESS
    The PROCESS option may be set to contain the name(s) of template files (relative to INCLUDE_PATH) which should be processed instead of the main template passed to the Template::Service process() method. This can be used to apply consistent wrappers around all templates, similar to the use of PRE_PROCESS and POST_PROCESS templates.

        my $service = Template::Service->new({
            PROCESS  => 'content',
        };

        # processes 'content' instead of 'foo.html'
        $service->process('foo.html');

    A reference to the original template is available in the 'template' variable. Metadata items can be inspected and the template can be processed by specifying it as a variable reference (i.e. prefixed by '$') to an INCLUDE, PROCESS or WRAPPER directive.

    content:

        <html>
        <head>
        <title>[% template.title %]</title>
        </head>

        <body>
        [% PROCESS $template %]
        <hr>
        &copy; Copyright [% template.copyright %]
        </body>
        </html>

    foo.html:

        [% META
           title     = 'The Foo Page'
           author    = 'Fred Foo'
           copyright = '2000 Fred Foo'
        %]
        <h1>[% template.title %]</h1>
        Welcome to the Foo Page, blah blah blah

    output:

        <html>
        <head>
        <title>The Foo Page</title>
        </head>

        <body>
        <h1>The Foo Page</h1>
        Welcome to the Foo Page, blah blah blah
        <hr>
        &copy; Copyright 2000 Fred Foo
        </body>
        </html>

ERROR
    The ERROR (or ERRORS if you prefer) configuration item can be used to name a single template or specify a hash array mapping exception types to templates which should be used for error handling. If an uncaught exception is raised from within a template then the appropriate error template will instead be processed.

    If specified as a single value then that template will be processed for all uncaught exceptions.

        my $service = Template::Service->new({
            ERROR => 'error.html'
        });

    If the ERROR item is a hash reference the keys are assumed to be exception types and the relevant template for a given exception will be selected. A 'default' template may be provided for the general case. Note that 'ERROR' can be pluralised to 'ERRORS' if you find it more appropriate in this case.

        my $service = Template::Service->new({
            ERRORS => {
                user     => 'user/index.html',
                dbi      => 'error/database',
                default  => 'error/default',
            },
        });

    In this example, any 'user' exceptions thrown will cause the 'user/index.html' template to be processed, 'dbi' errors are handled by 'error/database' and all others by the 'error/default' template. Any PRE_PROCESS and/or POST_PROCESS templates will also be applied to these error templates.

    Note that exception types are hierarchical and a 'foo' handler will catch all 'foo.*' errors (e.g. foo.bar, foo.bar.baz) if a more specific handler isn't defined. Be sure to quote any exception types that contain periods to prevent Perl concatenating them into a single string (i.e. "user.passwd" is parsed as 'user'.'passwd').

        my $service = Template::Service->new({
            ERROR => {
                'user.login'  => 'user/login.html',
                'user.passwd' => 'user/badpasswd.html',
                'user'        => 'user/index.html',
                'default'     => 'error/default',
            },
        });

    In this example, any template processed by the $service object, or other templates or code called from within, can raise a 'user.login' exception and have the service redirect to the 'user/login.html' template. Similarly, a 'user.passwd' exception has a specific handling template, 'user/badpasswd.html', while all other 'user' or 'user.*' exceptions cause a redirection to the 'user/index.html' page. All other exception types are handled by 'error/default'.

    Exceptions can be raised in a template using the THROW directive,

        [% THROW user.login 'no user id: please login' %]

    or by calling the throw() method on the current Template::Context object,

        $context->throw('user.passwd', 'Incorrect Password');
        $context->throw('Incorrect Password');    # type 'undef'

    or from Perl code by calling die() with a Template::Exception object,

        die (Template::Exception->new('user.denied', 'Invalid User ID'));

    or by simply calling die() with an error string. This is automagically caught and converted to an exception of 'undef' type which can then be handled in the usual way.

        die "I'm sorry Dave, I can't do that";

AUTO_RESET
    The AUTO_RESET option is set by default and causes the local BLOCKS cache for the Template::Context object to be reset on each call to the Template process() method. This ensures that any BLOCKs defined within a template will only persist until that template is finished processing. This prevents BLOCKs defined in one processing request from interfering with other independent requests subsequently processed by the same context object.

    The BLOCKS item may be used to specify a default set of block definitions for the Template::Context object. Subsequent BLOCK definitions in templates will over-ride these but they will be reinstated on each reset if AUTO_RESET is enabled (default), or if the Template::Context reset() method is called.

DEBUG
    The DEBUG option can be used to enable debugging messages from the Template::Service module by setting it to include the DEBUG_SERVICE value.

        use Template::Constants qw( :debug );

        my $template = Template->new({
            DEBUG => DEBUG_SERVICE,
        });

  process($input, \%replace)
The process() method is called to process a template specified as the first parameter, $input. This may be a file name, file handle (e.g. GLOB or IO::Handle) or a reference to a text string containing the template text. An additional hash reference may be passed containing template variable definitions.

The method processes the template, adding any PRE_PROCESS or POST_PROCESS templates defined, and returns the output text. An uncaught exception thrown by the template will be handled by a relevant ERROR handler if defined. Errors that occur in the PRE_PROCESS or POST_PROCESS templates, or those that occur in the main input template and aren't handled, cause the method to return undef to indicate failure. The appropriate error message can be retrieved via the error() method.

    $service->process('myfile.html', { title => 'My Test File' })
        || die $service->error();

  context()
Returns a reference to the internal context object which is, by default, an instance of the Template::Context class.

  error()
Returns the most recent error message.

AUTHOR
Andy Wardley <abw@wardley.org>

<http://wardley.org/|http://wardley.org/>

VERSION
2.93, distributed as part of the Template Toolkit version 2.19, released on 27 April 2007.

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.

SEE ALSO
Template, Template::Context