Question

I’m trying to implement a RESTful API in Perl. My current idea is to simply parse the path_info with a regex then dispatch the request to the appropriate subroutine which will then spit out the JSON, XML or even XHTML for the requested resource.

For example to retrieve info about user 1234 the RESTful client should find it at:

http://example.com/model.pl/users/1234

Below is the skeleton code of my first attempt at implementing a RESTful API:

model.pl :

#!/usr/bin/perl -w
use strict;
use CGI;

my $q = CGI->new();

print $q->header('text/html');

my $restfuluri  = $q->path_info;

if      ($restfuluri =~ /^\/(questions)\/([1-9]+$)/) { questions($1, $2); }
elsif   ($restfuluri =~ /^\/(users)\/([1-9]+$)/)     { users($1, $2); }


sub questions
{
      my $object = shift;
      my $value  = shift;

      #This is a stub, spits out JSON or XML when implemented.
      print $q->p("GET question : $object -> $value");
}

sub users
{
      my $object = shift;
      my $value  = shift;

      #This is a stub, spits out JSON or XML when implemented.
      print $q->p("GET user: $object -> $value");
}

Before I proceed any further, I would like to hear from experienced Perl hackers whether I got the basic idea right and if there are any serious shortcomings with this approach in terms of performance.

I can imagine, after a while, the if/else block would grow really large.

Looking forward to hear your views to make this code better.

Answer 1

I would use something like CGI::Application::Dispatch, it lets me build a dispatch table with variables and REST methods, and lets you use CGI and CGI::Application modules from CPAN. E.g.:

table => [
'/questions/:id[get]'    => { rm => 'get_question' },
'/users/:id[get]'        => { rm => 'get_user' }, # OR
':app/:id[post]'         => { rm => 'update' }, # where :app is your cgi application module
':app/:id[delete]'       => { rm => 'delete' },
],

(or you can use auto_rest or auto_rest_lc)

you can use a separate CGI::Application class for each type of thing (or just use classes in your cgi-app controller class methods).

CGI::Application also comes with plugins for outputting XML, JSON or text generated from templates.

cgi-app (and c::a::d) are are CGI applications and can be used with (little or) no change under CGI, FastCGI or mod_perl. C::A::D is also a mod_perl PerlHandler by default too.