NAME

HTTP::Proxy::HeaderFilter - A base class for HTTP message header filters

SYNOPSIS

    package MyFilter;

    use base qw( HTTP::Proxy::HeaderFilter );

    # changes the User-Agent header in all requests
    # this filter must be pushed on the request stack
    sub filter {
        my ( $self, $headers, $message ) = @_;

        $message->headers->header( User_Agent => 'MyFilter/1.0' );
    }

1;

DESCRIPTION

The HTTP::Proxy::HeaderFilter class is used to create filters for HTTP request/response headers.

Creating a HeaderFilter

A HeaderFilter is just a derived class that implements some methods called by the proxy. Of all the methods presented below, only filter() must be defined in the derived class.

filter()

The signature of the filter() method is the following:

    sub filter { my ( $self, $headers, $message) = @_; ... }

where $self is the filter object, $headers is a HTTP::Headers object, and $message is either a HTTP::Request or a HTTP::Response object.

The $headers HTTP::Headers object is the one that will be sent to the client (if the filter is on the response stack) or origin server (if the filter is on the request stack). If $headers is modified by the filter, the modified headers will be sent to the client or server.

The init() method (if it exists) is called by the new() constructeur to perform all initisalisation tasks. It's called once in the filter lifetime.

A HTTP::Proxy::HeaderFilter object is a blessed hash, and the base class reserves only hash keys that start with _hphf.

new()

The constructor is defined for all subclasses. Initialisation tasks (if any) for subclasses should be done in the init() method (see below).

init()

This method is called by the new() constructeur to perform all initisalisation tasks. It's called once in the filter lifetime.

It receives all the parameters passed to new().

Standard HeaderFilters

Standard HTTP::Proxy::HeaderFilter classes are lowercase.

The following HeaderFilters are included in the HTTP::Proxy distribution:

simple: This class lets you create a simple header filter from a code reference.
standard: This is the filter that provides standard headers handling for HTTP::Proxy. It is loaded automatically by HTTP::Proxy.

Please read each filter's documentation for more details about their use.

USEFUL METHODS FOR SUBCLASSES

Some methods are available to filters, so that they can eventually use the little knowledge they might have of HTTP::Proxy's internals. They mostly are accessors.

proxy(): Gets a reference to the HTTP::Proxy objects that owns the filter. This gives access to some of the proxy methods.

AUTHOR

Philippe ``BooK'' Bruhat, <book@cpan.org>.

COPYRIGHT

LICENSE

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

HTTP::Proxy::HeaderFilter - A base class for HTTP message header filters