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Plack-Middleware-Negotiate-0.04
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/ Plack::Middleware::Negotiate

NAME

Plack::Middleware::Negotiate - Apply HTTP content negotiation as Plack middleware

VERSION

version 0.04

SYNOPSIS

builder {
    enable 'Negotiate',
        formats => {
            xml  => { 
                type    => 'application/xml',
                charset => 'utf-8',
            },
            html => { type => 'text/html', language => 'en' },
            _    => { size => 0 }  # default values for all formats           
        },
        parameter => 'format', # e.g. http://example.org/foo?format=xml
        extension => 'strip';  # e.g. http://example.org/foo.xml
    $app; # neither html nor xml requested
};

DESCRIPTION

Plack::Middleware::Negotiate applies HTTP content negotiation to a PSGI request. The PSGI environment key negotiate.format is set to the chosen format name. In addition to normal content negotiation one may enable explicit format selection with a path extension or query parameter. The middleware takes care for rewriting and restoring PATH_INFO if it is configured to detect and strip a format extension. The PSGI response is enriched with corresponding HTTP headers Content-Type and Content-Language unless these headers already exist.

If used as pure application, this middleware returns a HTTP status code 406 if no format could be negotiated.

METHODS

new ( formats => { ... } [ %argument ] )

Creates a new negotiation middleware with a given set of formats. The argument parameter can be added to support explicit format selection with a query parameter. The argument extension can be used to support explicit format selection with a virtual file extension. Use format => 'strip' to strip a known format name from the request path and format => 'keep' to keep it. Each format can be defined with type, quality (defaults to 1), encoding, charset, and language. The special format name _ (underscore) is reserved to define default values for all formats.

Formats can also be used to directly route the request to a PSGI application:

my $app = Plack::Middleware::Negotiate->new(
    formats => {
        json => { 
            type => 'application/json',
            app  => $json_app,
        },
        html => {
            type => 'text/html',
            app  => $html_app,
        }
    }
);

negotiate ( $env )

Chooses a format based on a PSGI request. The request is first checked for explicit format selection via parameter and extionsion (if configured) and then passed to HTTP::Negotiate. Returns the format name. May modify the PSGI request environment keys PATH_INFO and SCRIPT_NAME if format was selected by extension set to strip.

about ( $format )

If the format was specified, this method returns a hash with quality, type, encoding, charset, and language. Missing values are set to the default.

variants ()

Returns a list of content variants to be used in HTTP::Negotiate. The return value is an array reference of array references, each with seven elements: format name, source quality, type, encoding, charset, language, and size. The size is always zero.

add_headers ( \@headers, $format )

Add apropriate HTTP response headers for a format unless the headers are already given.

METHODS

LOGGING AND DEBUGGUNG

Plack::Middleware::Negotiate uses Log::Contextual to emit a logging message during content negotiation on logging level <trace>. Just set:

$ENV{PLACK_MIDDLEWARE_NEGOTIATE_TRACE} = 1;

LIMITATIONS

The Content-Encoding HTTP response header is not automatically set on a response and content negotiation based on size is not supported. Feel free to comment on whether and how this middleware should support both.

SEE ALSO

HTTP::Negotiate, HTTP::Headers::ActionPack::ContentNegotiation

AUTHOR

Jakob Voß <voss@gbv.de>

COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Jakob Voß.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.