Is it required to map a Plack/PSGI middleware?

tiny_monk has asked for the wisdom of the Perl Monks concerning the following question:

Hello, Perl monks. I was able to write and run a PSGI middleware that validates a form. However, the problem is that I am not sure whether I did it correctly. What I did is that I mapped the middleware, $form_validator, instead of the wrapped PSGI application, $greeting. My code below will display a simple HTML form with a field name 'Taste of Vinegar' and a submit button. When you type in 'sour' and submit the form, the middleware, $form_validator, will be invoked to perform the validation. If all is well, then the PSGI application, $greeting, will be invoked. I am new to Perl/PSGI and I am not sure if I'm doing this correctly. I'd appreciate all of your comments on this. Best regards. :)


#!/usr/bin/perl

use strict;
use warnings;

use Plack::Request;
use Plack::Response;

        my $greeting = sub {
        
                    return [
                            '200',
                            [ 'Content-Type' => 'text/html' ],
                            [ "<html>
                                    <body>
                                        <p>Congratulations! Your answe
+r is correct!</p>
                                    </body>
                              </html>"],
                            ];
        
        };
        
        
        my $form_validator = sub {
        
            my $env = shift;                                 # PSGI en
+v
            my $request = Plack::Request->new($env);         # new Pla
+ck::Request
            
            my $taste = $request->param('taste');
            
            if ($taste eq 'sour') {
                return $greeting->($env);
                        
            }
            else
            {
                my $response = $request->new_response(200);;         #
+ new Plack::Response
                 $response->headers({ 'Content-Type' => 'text/html' })
+;
                $response->content('<html><body><p>Wrong answer!</p></
+body></html>' );
                return $response->finalize;    
            }
            
        };




        my $form = sub {
            
            return [
                    200, 
                    ['Content-Type' => 'text/html'],
                    ["<html>
                        <body>
                            <form action='submit' method='GET'>
                            Taste of Vinegar <input type='text' name='
+taste'/>
                            <input type='submit' value='SUBMIT' />
                            </form>
                        </body>
                    </html>"]
                    ];
        
        };






        my %routing = (
                '/submit' => $form_validator,
                '/' => $form,            
                );


        my $app = sub {
 
            my $env = shift;    # PSGI env
            my $request = Plack::Request->new($env);
            my $route = $routing{$request->path_info};
            
            if ($route) {return $route->($env);}
            else 
                {
                    return [
                            '404',
                            [ 'Content-Type' => 'text/html' ],
                            [ '404 Not Found' ],
                            ];
                }
        };
[download]

Comment on Is it required to map a Plack/PSGI middleware? Download Code

Replies are listed 'Best First'.
Re: Is it required to map a Plack/PSGI middleware? by Anonymous Monk on Sep 12, 2015 at 03:17 UTC
Since you're already using Plack, why aren't you using Plack::Builder / Plack::Middleware ?	[reply]
Re^2: Is it required to map a Plack/PSGI middleware? by tiny_monk (Sexton) on Sep 12, 2015 at 03:34 UTC
That's a good question. It's because at this point I'm still learning how to write my own middleware. I don't think the Perl Advent Calendar requires the use of those modules if one is merely writing one's own middleware. :) I'd appreciate your further comment. Thank you.	[reply]
Re^3: Is it required to map a Plack/PSGI middleware? by Anonymous Monk on Sep 12, 2015 at 07:28 UTC
Um, read http://advent.plackperl.org/2009/12/day-23-write-your-own-middleware.html	[reply]
Re^4: Is it required to map a Plack/PSGI middleware? by tiny_monk (Sexton) on Sep 12, 2015 at 10:38 UTC
Re^5: Is it required to map a Plack/PSGI middleware? by Anonymous Monk on Sep 12, 2015 at 21:28 UTC
Some notes below your chosen depth have not been shown here
Re: Is it required to map a Plack/PSGI middleware? by Anonymous Monk on Sep 12, 2015 at 03:14 UTC
What means "mapped"? See Middleware of PSGI	[reply]
Re^2: Is it required to map a Plack/PSGI middleware? by tiny_monk (Sexton) on Sep 12, 2015 at 03:29 UTC
Mapping in this case simply means the routing or the redirection of a request. I included a dispatch table in the code: `my %routing = ( '/submit' => $form_validator, '/' => $form, );` [download] When you submit the HTML form, it is sent to the URL '/submit' as defined by the HTML form attribute 'action'. Since '/submit' is associated with $form_validator, the anonymous function that the $form_validator refers to is invoked.	[reply] [d/l]