Plack::Middleware::Negotiate - Apply HTTP content negotiation as Plack middleware
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; };
Plack::Middleware::Negotiate applies HTTP content negotiation to a PSGI request. In addition to normal content negotiation from a list of defined formats one may enable explicit format selection with a path extension or query parameter. In summary, the following methods are tried in this order to negotiate a known format:
formats
extension
parameter
e.g. format is set to xml for http://example.org/foo?format=xml if format xml has been defined.
e.g. format is set to xml for http://example.org/foo.xml if format xml has been defined.
explicit
e.g. format is set to xml if format xml has been defined with content type application/xml for Accept header value "application/xml".
The PSGI environment key negotiate.format is set to the chosen format name after negotiation. The PSGI response is enriched with corresponding HTTP headers Content-Type and Content-Language unless these headers already exist.
negotiate.format
If used as pure application, this middleware returns a HTTP status code 406 if no format could be negotiated.
Creates a new negotiation middleware with a given set of formats.
Chooses a format based on a PSGI request. The request is first checked for explicit format selection via parameter and extension (if configured) and then passed to HTTP::Negotiate. On success the method returns a format name. The method may modify the PSGI request environment keys PATH_INFO and SCRIPT_NAME if format was selected by extension set to strip, and strips the format HTTP GET query parameter from QUERY_STRING if parameter is set to a format. If format was selected by HTTP POST body parameter, the parameter it is not stripped from the request.
strip
format
Tells whether a format name is known. By default this is the case if the format name exists in the list of formats.
If the format was specified, this method returns a hash with quality, type, encoding, charset, and language. Missing values are set to the default.
quality
type
encoding
charset
language
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 apropriate HTTP response headers for a format unless the headers are already given.
A list of formats to choose among. 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, } } );
Enables explicit format selection with a query paramater, for instance format. Both HTTP GET and HTTP POST body parameters are supported.
Enables explicit format selection with a virtual file extension. The value strip strips a known format name from the request path. The value keep keeps the format name extension after format selection.
keep
The middleware takes care for rewriting and restoring PATH_INFO if it is configured to detect and strip a format extension.
Disables content negotiation based on HTTP headers.
Plack::Middleware::Negotiate uses Log::Contextual to emit a logging message during content negotiation on logging level trace. Just set:
Log::Contextual
trace
$ENV{PLACK_MIDDLEWARE_NEGOTIATE_TRACE} = 1;
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.
Jakob Voß, Christopher A. Kirke
Copyright 2014- Jakob Voß
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
Content negotiation in this module is based on HTTP::Negotiate. See HTTP::Headers::ActionPack::ContentNegotiation for an alternative approach. This module has some overlap with Plack::Middleware::SetAccept.
To install Plack::Middleware::Negotiate, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Plack::Middleware::Negotiate
CPAN shell
perl -MCPAN -e shell install Plack::Middleware::Negotiate
For more information on module installation, please visit the detailed CPAN module installation guide.