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.\" ========================================================================
.\"
.IX Title "Web::Machine::Manual 3pm"
.TH Web::Machine::Manual 3pm "2017-01-26" "perl v5.24.1" "User Contributed Perl Documentation"
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.SH "NAME"
Web::Machine::Manual \- Learn how to use Web::Machine
.SH "VERSION"
.IX Header "VERSION"
version 0.17
.SH "Web::Machine IN A NUTSHELL"
.IX Header "Web::Machine IN A NUTSHELL"
The basic idea behind \f(CW\*(C`Web::Machine\*(C'\fR 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 \s-1GET, POST, PUT,\s0
etc.? Does the request ask for a content type our resource provides?
.PP
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 Plack and
\&\s-1PSGI\s0 <http://plackperl.org/>, the response consists of a status code, some
headers, and an optional body.
.PP
The best way to understand the full request/response cycle is to look at the
original Erlang webmachine state
diagram <https://github.com/basho/webmachine/wiki/Diagram>. Each diamond in that
diagram corresponds to a method that your Web::Machine::Resource subclass
can implement. The return value from your method determines what method to call
next.
.PP
However, unlike on that diagram, we often support return values beyond simple
true/false values for methods. The Web::Machine::Resource documentation
describes what each method can return.
.SH "Web::Machine and Plack"
.IX Header "Web::Machine and Plack"
\&\f(CW\*(C`Web::Machine\*(C'\fR is built on top of Plack and follows the
\&\s-1PSGI\s0 <http://plackperl.org/> spec. You can mix \f(CW\*(C`Web::Machine\*(C'\fR applications
with other Plack applications using standard Plack tools like Plack::Builder.
.SS "Web::Machine and Plack Middleware"
.IX Subsection "Web::Machine and Plack Middleware"
Since \f(CW\*(C`Web::Machine\*(C'\fR implements the complete request and response
cycle, some Plack middleware is not really needed with \f(CW\*(C`Web::Machine\*(C'\fR. For
example, it wouldn't make sense to use something like
\&\f(CW\*(C`Plack::Middleware::XSLT\*(C'\fR with \f(CW\*(C`Web::Machine\*(C'\fR. \f(CW\*(C`Web::Machine\*(C'\fR implements
the full content negotiation process, so if you want to handle requests for
\&\f(CW\*(C`text/html\*(C'\fR it probably makes more sense to do this in your resources. The
benefit of doing so is that with \f(CW\*(C`Web::Machine\*(C'\fR you can easily ensure that
you return a proper \f(CW\*(C`406 Not Acceptable\*(C'\fR status for content types you
\&\fIcan't\fR handle.
.PP
There are still many pieces of Plack middleware that are useful with
\&\f(CW\*(C`Web::Machine\*(C'\fR, such as logging middleware, debugging/linting middleware,
etc.
.PP
That all said, \f(CW\*(C`Web::Machine\*(C'\fR won't break if you use an inappropriate
middleware; you'll just lose some of the benefits you get from implementing
things the \f(CW\*(C`Web::Machine\*(C'\fR way.
.SS "Bodies Must be Bytes"
.IX Subsection "Bodies Must be Bytes"
The \s-1PSGI\s0 spec requires that the body you return contain bytes, not Perl
characters. In other words, strings you return must be passed through
\&\f(CW\*(C`Encode::encode\*(C'\fR so that Perl interprets their contents as bytes.
.PP
If your data is not binary or \s-1ASCII,\s0 your resource should make sure to provide
\&\f(CW\*(C`charset_provided()\*(C'\fR and \f(CW\*(C`default_charset()\*(C'\fR methods. This will make sure
that \f(CW\*(C`Web::Machine\*(C'\fR knows how to turn your response bodies into bytes.
.PP
\&\fB\s-1CAVEAT:\s0\fR Note that currently \f(CW\*(C`Web::Machine\*(C'\fR does not provide full charset
or encoding support when the body is returned as a \s-1CODE\s0 ref. This is a bug to
be remedied in the future, but currently you are responsible for making sure
this code ref returns bytes.
.SH "SUPPORT"
.IX Header "SUPPORT"
bugs may be submitted through <https://github.com/houseabsolute/webmachine\-perl/issues>.
.SH "AUTHORS"
.IX Header "AUTHORS"
.IP "\(bu" 4
Stevan Little <stevan@cpan.org>
.IP "\(bu" 4
Dave Rolsky <autarch@urth.org>
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
This software is copyright (c) 2016 by Infinity Interactive, Inc.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.