libweb-machine-perl 0.17-1 / usr / share / perl5 / Web / Machine / Manual.pod

package Web::Machine::Manual;
#ABSTRACT: Learn how to use Web::Machine

__END__

=pod

=encoding UTF-8

=head1 NAME

Web::Machine::Manual - Learn how to use Web::Machine

=head1 VERSION

version 0.17

=head1 Web::Machine IN A NUTSHELL

The basic idea behind C<Web::Machine> is that the handling of a web request
is implemented as a state machine. If you're not familiar with state machines,
think of a flowchart. We look at the request and the resource we provide and
ask questions about them. Is our service available? Is this a GET, POST, PUT,
etc.? Does the request ask for a content type our resource provides?

The result of each question leads us to the next state (or flowchart
box). Eventually we reach a point where we have a response for the
client. Since this is all built on top of L<Plack> and
L<PSGI|http://plackperl.org/>, the response consists of a status code, some
headers, and an optional body.

The best way to understand the full request/response cycle is to look at the
original L<Erlang webmachine state
diagram|https://github.com/basho/webmachine/wiki/Diagram>. Each diamond in that
diagram corresponds to a method that your L<Web::Machine::Resource> subclass
can implement. The return value from your method determines what method to call
next.

However, unlike on that diagram, we often support return values beyond simple
true/false values for methods. The L<Web::Machine::Resource> documentation
describes what each method can return.

=head1 Web::Machine and Plack

C<Web::Machine> is built on top of Plack and follows the
L<PSGI|http://plackperl.org/> spec. You can mix C<Web::Machine> applications
with other Plack applications using standard Plack tools like L<Plack::Builder>.

=head2 Web::Machine and Plack Middleware

Since C<Web::Machine> implements the complete request and response
cycle, some L<Plack> middleware is not really needed with C<Web::Machine>. For
example, it wouldn't make sense to use something like
C<Plack::Middleware::XSLT> with C<Web::Machine>. C<Web::Machine> implements
the full content negotiation process, so if you want to handle requests for
C<text/html> it probably makes more sense to do this in your resources. The
benefit of doing so is that with C<Web::Machine> you can easily ensure that
you return a proper C<406 Not Acceptable> status for content types you
I<can't> handle.

There are still many pieces of L<Plack> middleware that are useful with
C<Web::Machine>, such as logging middleware, debugging/linting middleware,
etc.

That all said, C<Web::Machine> won't break if you use an inappropriate
middleware; you'll just lose some of the benefits you get from implementing
things the C<Web::Machine> way.

=head2 Bodies Must be Bytes

The PSGI spec requires that the body you return contain bytes, not Perl
characters. In other words, strings you return must be passed through
C<Encode::encode> so that Perl interprets their contents as bytes.

If your data is not binary or ASCII, your resource should make sure to provide
C<charset_provided()> and C<default_charset()> methods. This will make sure
that C<Web::Machine> knows how to turn your response bodies into bytes.

B<CAVEAT:> Note that currently C<Web::Machine> does not provide full charset
or encoding support when the body is returned as a CODE ref. This is a bug to
be remedied in the future, but currently you are responsible for making sure
this code ref returns bytes.

=head1 SUPPORT

bugs may be submitted through L<https://github.com/houseabsolute/webmachine-perl/issues>.

=head1 AUTHORS

=over 4

=item *

Stevan Little <stevan@cpan.org>

=item *

Dave Rolsky <autarch@urth.org>

=back

=head1 COPYRIGHT AND LICENCE

This software is copyright (c) 2016 by Infinity Interactive, Inc.

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

=cut