Cro::HTTP::BodyParser::JSONClass

Parse and deserialise application/json HTTP body to a specified JSON::Class

Synopsis

use Cro::HTTP::Router;
use Cro::HTTP::Server;
use JSON::Class;
use Cro::HTTP::BodyParser::JSONClass;


class HelloClass does JSON::Class {
    has Str $.firstname;
    has Str $.lastname;

    method hello(--> Str ) {
        "Hello, $.firstname() $.lastname()";
    }

}

# This intermediate class is only necessary in older rakudo, as of
# 2021.09 the parameterised role can be use directly
class SomeBodyParser does Cro::HTTP::BodyParser::JSONClass[HelloClass] {
}

my $app = route {
    body-parser SomeBodyParser;
    post -> 'hello' {
        request-body -> $hello {
            content 'text/plain', $hello.hello;
        }
    }
};

my Cro::Service $service = Cro::HTTP::Server.new(:host<127.0.0.1>, :port<7798>, application => $app);

$service.start;

react  { whenever signal(SIGINT) { $service.stop; exit; } }

use Cro::HTTP::Client;
use JSON::Class;
use Cro::HTTP::BodyParser::JSONClass;

my $client1 = Cro::HTTP::Client.new: body-parsers => [Cro::HTTP::BodyParser::JSONClass[HelloClass]];
my $obj1 = await $client1.get-body: 'https://jsonclass.free.beeceptor.com/hello';
say $obj1.raku;
=output HelloClass.new(firstname => "fname", lastname => "lname")␤

# Setting the JSON class after creating an instance of Cro::HTTP::Client
my $body-parser = Cro::HTTP::BodyParser::JSONClass.new;
my $client2 = Cro::HTTP::Client.new: body-parsers => [$body-parser];
$body-parser.set-json-class: HelloClass;
my $obj2 = await $client2.get-body: 'https://jsonclass.free.beeceptor.com/hello';
say $obj2.raku;
=output HelloClass.new(firstname => "fname", lastname => "lname")␤

Description

This provides a specialised Cro::BodyParser that will parse a JSON ('application/json') request body to the specified JSON::Class type. This is useful if you have JSON::Class classes that you want to create from HTTP data, and will lead to less code and perhaps better abstraction.

The BodyParser is implemented as a Parameterised Role with the target class as the parameter. Because this will basically over-ride the Cro's builtin JSON parsing it probably doesn't want to be installed at the top level in the Cro::HTTP instance, but rather in a specific route block with the body-parser helper, also because it is specialised to a single class it may want to be isolated to its own route block so other routes keep the default behaviour or have parsers parameterised to different classes, so you may want to do something like:

my $app = route {
    delegate 'hello' => route {
        body-parser SomeBodyParser;
        post ->  {
            request-body -> $hello {
                content 'text/plain', $hello.hello;
            }
        }
    }
};

The test as to whether this body parser should be used (defined in the method is-applicable ) is generalised to the application/json content type, (hence the caveat above regarding reducing the scope.) If you want to make a more specific test (or even if the Content-Type supplied isn't application/json,) then you can compose this to a new class the over-rides the is-applicable:

class SomeBodyParser does Cro::HTTP::BodyParser::JSONClass[HelloClass] {
   method is-applicable(Cro::HTTP::Message $message --> Bool) {
      $message.header('X-API-Message-Type').defined && $message.header('X-API-Message-Type') eq 'Hello';
   }
}

And then use SomeBodyParser in place of Cro::HTTP::BodyParser::JSONClass.

The BodyParser has a set-json-class method which can be used to set the JSON::Class class to another class whenever needed.

Installation

Assuming you have a working installation of rakudo you should be able to install this with zef :

zef install Cro::HTTP::BodyParser::JSONClass

Or from a local clone of the repository:

zef install .

Support

Please direct any patches, suggestions or feedback to Github.

Licence and copyright

This is free software, please see the LICENCE file in the distribution.

© Jonathan Stowe 2021