NAME

Plack::Middleware - Base class for easy-to-use PSGI middleware

SYNOPSIS

  package Plack::Middleware::Foo;
  use parent qw( Plack::Middleware );

  sub call {
      my($self, $env) = @_;
      # Do something with $env

      # $self->app is the original app
      my $res = $self->app->($env);

      # Do something with $res
      return $res;
  }

  # then in app.psgi
  use Plack::Builder;

  my $app = sub { ... } # as usual

  builder {
      enable "Plack::Middleware::Foo";
      enable "Plack::Middleware::Bar", %options;
      $app;
  };

DESCRIPTION

Plack::Middleware is an utility base class to write PSGI middleware. All you have to do is to inherit from Plack::Middleware and then implement the callback call method (or to_app method that would return the PSGI code reference) to do the actual work. You can use $self->app to call the original (wrapped) application.

See Plack::Builder how to actually enable middlewares in your .psgi application file using the DSL. If you do not like our builder DSL, you can also use wrap method to wrap your application with a middleware:

  use Plack::Middleware::Foo;

  my $app = sub { ... };
  $app = Plack::Middleware::Foo->wrap($app, %options);
  $app = Plack::Middleware::Bar->wrap($app, %options);

Note also Plack::Middleware object is callable, by overloading the code dereference, so:

  package Plack::Middleware::Foo;
  use parent qw(Plack::Middleware);

  sub call { ... }

  my $app = Plack::Middleware::Foo->new;

$app here is an object but can be used as a PSGI application as well, since $app->($env) just calls $app->call($env) internally.

SEE ALSO

Plack Plack::Builder