5 Catalyst::PSGI - How Catalyst and PSGI work together
9 The L<PSGI> specification defines an interface between web servers and
10 Perl-based web applications and frameworks. It supports the writing of
11 portable applications that can be run using various methods (as a
12 standalone server, or using mod_perl, FastCGI, etc.). L<Plack> is an
13 implementation of the PSGI specification for running Perl applications.
15 Catalyst used to contain an entire set of C<< Catalyst::Engine::XXXX >>
16 classes to handle various web servers and environments (e.g. CGI,
17 FastCGI, mod_perl) etc.
19 This has been changed in Catalyst 5.9 so that all of that work is done
20 by Catalyst implementing the L<PSGI> specification, using L<Plack>'s
21 adaptors to implement that functionality.
23 This means that we can share common code, and share fixes for specific
26 =head1 I already have an application
28 If you already have a Catalyst application, then you should be able to
29 upgrade to the latest release with little or no trouble (see the notes
30 in L<Catalyst::Upgrading> for specifics about your web server
33 =head1 Writing your own PSGI file.
35 =head2 What is a .psgi file?
37 A C<< .psgi >> file lets you control how your application code reference
38 is built. Catalyst will automatically handle this for you, but it's
39 possible to do it manually by creating a C<myapp.psgi> file in the root
42 =head2 Why would I want to write my own .psgi file?
44 Writing your own .psgi file allows you to use the alternate L<plackup> command
45 to start your application, and allows you to add classes and extensions
46 that implement L<Plack::Middleware>, such as L<Plack::Middleware::ErrorDocument>
47 or L<Plack::Middleware::AccessLog>.
49 The simplest C<.psgi> file for an application called C<TestApp> would be:
55 my $app = TestApp->psgi_app(@_);
57 Note that Catalyst will apply a number of middleware components for you
58 automatically, and these B<will not> be applied if you manually create a
59 psgi file yourself. Details of these components can be found below.
61 Additional information about psgi files can be found at:
62 L<http://search.cpan.org/dist/Plack/lib/Plack.pm#.psgi_files>
64 =head2 What is in the .psgi file Catalyst generates by default?
66 Catalyst generates an application which, if the C<using_frontend_proxy>
67 setting is on, is wrapped in L<Plack::Middleware::ReverseProxy>, and
68 contains some engine-specific fixes for uniform behaviour, as contained
73 =item L<Plack::Middleware::LighttpdScriptNameFix>
75 =item L<Plack::Middleware::IIS6ScriptNameFix>
79 If you override the default by providing your own C<< .psgi >> file,
80 then none of these things will be done automatically for you by the PSGI
81 application returned when you call C<< MyApp->psgi_app >>. Thus, if you
82 need any of this functionality, you'll need to implement this in your
83 C<< .psgi >> file yourself.
85 An apply_default_middlewares method is supplied to wrap your application
86 in the default middlewares if you want this behaviour and you are providing
89 This means that the auto-generated (no .psgi file) code looks something
96 my $app = TestApp->apply_default_middlewares(TestApp->psgi_app(@_));
100 L<Catalyst::Upgrading>, L<Plack>, L<PSGI::FAQ>, L<PSGI>.
104 Catalyst Contributors, see Catalyst.pm
108 This library is free software. You can redistribute it and/or modify
109 it under the same terms as Perl itself.