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.\" ========================================================================
.\"
.IX Title "HTTP::Proxy::HeaderFilter 3pm"
.TH HTTP::Proxy::HeaderFilter 3pm "2017-06-28" "perl v5.20.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
HTTP::Proxy::HeaderFilter \- A base class for HTTP message header filters
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    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 => \*(AqMyFilter/1.0\*(Aq );
\&    }
\&
\&    1;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The HTTP::Proxy::HeaderFilter class is used to create filters for
\&\s-1HTTP\s0 request/response headers.
.SS "Creating a HeaderFilter"
.IX Subsection "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
\&\f(CW\*(C`filter()\*(C'\fR \fBmust\fR be defined in the derived class.
.IP "\fIfilter()\fR" 4
.IX Item "filter()"
The signature of the \f(CW\*(C`filter()\*(C'\fR method is the following:
.Sp
.Vb 1
\&    sub filter { my ( $self, $headers, $message) = @_; ... }
.Ve
.Sp
where \f(CW$self\fR is the filter object, \f(CW$headers\fR is a HTTP::Headers object,
and \f(CW$message\fR is either a HTTP::Request or a HTTP::Response object.
.Sp
The \f(CW$headers\fR HTTP::Headers object is the one that will be sent to
the client (if the filter is on the response stack) or origin
server (if the filter is on the request stack). If \f(CW$headers\fR is
modified by the filter, the modified headers will be sent to the
client or server.
.Sp
The \f(CW\*(C`init()\*(C'\fR method (if it exists) is called by the \f(CW\*(C`new()\*(C'\fR constructeur
to perform all initisalisation tasks. It's called once in the filter
lifetime.
.Sp
A HTTP::Proxy::HeaderFilter object is a blessed hash, and the base class
reserves only hash keys that start with \f(CW\*(C`_hphf\*(C'\fR.
.IP "\fInew()\fR" 4
.IX Item "new()"
The constructor is defined for all subclasses. Initialisation tasks
(if any) for subclasses should be done in the \f(CW\*(C`init()\*(C'\fR method (see below).
.IP "\fIinit()\fR" 4
.IX Item "init()"
This method is called by the \f(CW\*(C`new()\*(C'\fR constructeur to perform all
initisalisation tasks. It's called once in the filter lifetime.
.Sp
It receives all the parameters passed to \f(CW\*(C`new()\*(C'\fR.
.SS "Standard HeaderFilters"
.IX Subsection "Standard HeaderFilters"
Standard HTTP::Proxy::HeaderFilter classes are lowercase.
.PP
The following HeaderFilters are included in the HTTP::Proxy distribution:
.IP "simple" 4
.IX Item "simple"
This class lets you create a simple header filter from a code reference.
.IP "standard" 4
.IX Item "standard"
This is the filter that provides standard headers handling for HTTP::Proxy.
It is loaded automatically by HTTP::Proxy.
.PP
Please read each filter's documentation for more details about their use.
.SH "USEFUL METHODS FOR SUBCLASSES"
.IX Header "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.
.IP "\fIproxy()\fR" 4
.IX Item "proxy()"
Gets a reference to the HTTP::Proxy objects that owns the filter.
This gives access to some of the proxy methods.
.SH "AUTHOR"
.IX Header "AUTHOR"
Philippe \*(L"BooK\*(R" Bruhat, <book@cpan.org>.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
HTTP::Proxy, HTTP::Proxy::BodyFilter.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2003\-2013, Philippe Bruhat.
.SH "LICENSE"
.IX Header "LICENSE"
This module is free software; you can redistribute it or modify it under
the same terms as Perl itself.