Frank Wiles
and 1 contributors


ModPerl::ParamBuilder - Makes building custom Apache directives easy


   package MyApp::Parameters; 

   use ModPerl::ParamBuilder;

   use base qw( 'ModPerl::ParamBuilder' );

   my $builder = ModPerl::ParamBuilder->new( __PACKAGE__ ); 

   # Build simple one argument parameter
   $builder->param( 'Template'     );
   $builder->param( 'PageTitle'    );
   $builder->param( 'ItemsPerPage' );

   # Build an On/Off parameter
   $builder->on_off( 'Caching'     );

   # Build a Yes/No parameter 
   $builder->yes_no( 'AutoCommit'  ); 

   # Build a no argument/flag parameter
   $builder->no_arg( 'Active'      );

   # Build a one argument parameter with a custom error message
   # and special configuration hash key 
   $builder->param( {
                        name    => 'SMTPServer',
                        err     => 'SMTPServer xx.xx.xx.xx',
                        key     => 'smtp_server',

   # Load the configuration into Apache 

   # And elsewhere in your application
   package MyApp::Main;

   # Retrieve the configuration like so
   my $params   = MyApp::Parameters->new; 
   my $conf_ref = $params->get_config( $r ); 
   # Or if you have PerlOptions +GlobalRequest on then you can just
   # call 
   my $conf_ref = $params->get_config; 


One of the neatest features of mod_perl 2.0 is the ability to easily create your own custom Apache directives. Not only are they more efficient to use compared to PerlSetEnv, PerlPassEnv, PerlAddVar, and PerlSetVar, but they give your application a more polished and professional look and feel..

Not to mention they're just plain cool. This module aims to make the already easy, even easier.

Note that you MUST load your parameter module with PerlLoadModule in your httpd.conf and not PerlModule. This is necessary because Apache needs to load your module earlier than usual in the startup to be able to read it's own configuration now.



    package MyApp::Params;
    use base qw( ModPerl::ParamBuilder );
    my $builder = ModPerl::ParamBuilder->new( __PACKAGE__ ); 

This function creates a new ParamBuilder object. You must pass either the name of your application's parameter module or use the handy __PACKAGE__ built in.


This function is used to build the more general directives. To create a simple directive named Foo that takes one argument you simply call:

   $builder->param( 'Foo' ); 

Assuming you put your directives in MyApp::Parameters, you can then use Foo in Apache httpd.conf like so:

   PerlLoadModule MyApp::Parameters

   <Location /myapp> 
      SetHandler perl-script 
      Foo Bar 
      PerlResponseHandler MyApp::Main 

When you retrieve the configuration with get_config() Foo's argument will be stored in the hash key of the same name ( i.e. 'Foo' ).

param() can also take a hash of options that give you more access to using some more advanced features of Apache directives. The valid options are:

    name -- Name of the directive used in httpd.conf 
    key  -- Hash key to store this directives arguments in 
    err  -- Custom error message used with this directive 
    func -- Custom function used to process the directives on Apache 
            startup. See the mod_perl 2.0 documentation for more 
            information on how to use a custom function for 
            processing and/or validating the arguments 
    take -- How many arguments to take and which are required, etc. 

For example, if you wanted to create a directive named SMTPServers that took an arbitrarily long list of IP addresses of SMTP server your application should use, and you wanted it to be stored in the configuration as 'smtp_servers', it can be built like this:

                      name    => 'SMTPServers',
                      key     => 'smtp_servers',
                      err     => 'SMTPServers xx.xx.xx.xx yy.yy.yy.yy', 
                      take    => 'list',

This list of SMTP servers can then be retrieved like so:

   my $conf_ref = MyApp::Parameters->get_config; 

   my @smtp_servers = $$conf_ref{smtp_servers}; 

Because ModPerl::ParamBuilder will return a list to you in this case rather than a single value.

The valid options for take are:

 1    or one          -- Take one argument (default)
 2    or two          -- Take two arguments 
 3    or three        -- Take three arguments 
 12   or one_plus     -- One mandatory argument  with one optional 
 23   or two_plus     -- Two mandatory arguments with an optional third
 123  or one_plus_two -- One mandatory argument  with two optional ones

 list                 -- An arbitrarily long list of arguments 
 one_plus_list        -- One mandatory argument followed by an 
                         arbitrarily long list of additional 

no_arg( $name )

This allows you to define an Apache directive which takes no arguments. Each time this value is used the value in the configuration hash will be incremented. The value in the hash for the key $name will be undefined if it does not appear in httpd.conf

yes_no( $name )

This creates a simple Yes or No directive. The value in the configuration hash will be 1 ( Yes ) or 0 ( No ) depending on the definition in httpd.conf

on_off( $name )

This creates a simple On or Off directive. The value in the configuration hash will be 1 ( On ) or 0 ( No ), just like yes_no().


The biggest limitation is that this module ONLY works with mod_perl 2.0 and above. There are no plans to support mod_perl 1.x for this module, trust me you want to upgrade to mod_perl 2 as soon as you can.

This module's intent is not to replace the underlying mod_perl APIs nor is it intended to be used for complicated cases where special processing is needed. It is intended to make the simple things simple.

Some things to keep in mind when using ModPerl::ParamBuilder

This module does not restrict where the directives can be used in Apache's httpd.conf. To restrict directives to particular area ( only in main server conf, a VirtualHost, or a Location, etc ) you will need to use the mod_perl APIs to build your directives.

This also does not do, by default, any error checking or validation on the arguments passed to directives. If you create a directive 'NumberOfItemsPerPage' and then put:

     NumberOfItemsPerPage rhubarb 

Apache will not see this as an error and your configuration hash for the key 'NumberOfItemsPerPage' will contain the string 'rhubarb'. You can validate this data in three different ways:

    1) Validate the configuration data in your application prior to
       using it. 

    2) Instruct ModPerl::ParamBuilder to use a special function for
       processing the arguments by passing the 'func' option. 

    3) Revert to using the mod_perl API where you have more control.

See the appropriate mod_perl 2.0 API modules for how to accomplish more in depth processing of directives and their data.


None that I am aware of. Please report any you find to the E-mail address below.


Apache2::Module(3), Apache2::CmdParms(3), the examples/ directory of this module, and the mod_perl 2.0 documentation.


Frank Wiles <>


Revolution Systems, LLC. All rights reserved.


This software can be distributed under the same terms as Perl itself.