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OpenAPI::Client - A client for talking to an Open API powered server


OpenAPI::Client can generating classes that can talk to an Open API server. This is done by generating a custom class, based on a Open API specification, with methods that transform parameters into a HTTP request.

The generated class will perform input validation, so invalid data won't be sent to the server.

Note that this implementation is currently EXPERIMENTAL, but unlikely to change! Feedback is appreciated.


Open API specification

The specification given to "new" need to point to a valid OpenAPI document. This document can be OpenAPI v2.x or v3.x, and it can be in either JSON or YAML format. Example:

  openapi: 3.0.1
    title: Swagger Petstore
    version: 1.0.0
  - url:
        operationId: listPets

host, basePath and the first item in schemes will be used to construct "base_url". This can be altered at any time, if you need to send data to a custom endpoint.


The OpenAPI API specification will be used to generate a sub-class of OpenAPI::Client where the "operationId", inside of each path definition, is used to generate methods:

  use OpenAPI::Client;
  $client = OpenAPI::Client->new("file:///path/to/api.json");

  # Blocking
  $tx = $client->listPets;

  # Non-blocking
  $client = $client->listPets(sub { my ($client, $tx) = @_; });

  # Promises
  $promise = $client->listPets_p->then(sub { my $tx = shift });

  # With parameters
  $tx = $client->listPets({limit => 10});

See Mojo::Transaction for more information about what you can do with the $tx object, but you often just want something like this:

  # Check for errors
  die $tx->error->{message} if $tx->error;

  # Extract data from the JSON responses
  say $tx->res->json->{pets}[0]{name};

Check out "error" in Mojo::Transaction, "req" in Mojo::Transaction and "res" in Mojo::Transaction for some of the most used methods in that class.


Custom server URL

If you want to request a different server than what is specified in the Open API document, you can change the "base_url":

  # Pass on a Mojo::URL object to the constructor
  $base_url = Mojo::URL->new("");
  $client1 = OpenAPI::Client->new("file:///path/to/api.json", base_url => $base_url);

  # A plain string will be converted to a Mojo::URL object
  $client2 = OpenAPI::Client->new("file:///path/to/api.json", base_url => "");

  # Change the base_url after the client has been created
  $client3 = OpenAPI::Client->new("file:///path/to/api.json");

Custom content

You can send XML or any format you like, but this require you to add a new "generator":

  use Your::XML::Library "to_xml";
  $client->ua->transactor->add_generator(xml => sub {
    my ($t, $tx, $data) = @_;
    $tx->req->body(to_xml $data);
    return $tx;

  $client->addHero({}, xml => {name => "Supergirl"});

See Mojo::UserAgent::Transactor for more details.



  $client->on(after_build_tx => sub { my ($client, $tx) = @_ })

This event is emitted after a Mojo::UserAgent::Transactor object has been built, just before it is passed on to the "ua". Note that all validation has already been run, so alternating the $tx too much, might cause an invalid request on the server side.

A special "env" in Mojo::Message::Request variable will be set, to reference the operationId:


Note that this usage of env() is currently EXPERIMENTAL:



  $base_url = $client->base_url;

Returns a Mojo::URL object with the base URL to the API. The default value comes from schemes, basePath and host in the OpenAPI v2 specification or from servers in the OpenAPI v3 specification.


  $ua = $client->ua;

Returns a Mojo::UserAgent object which is used to execute requests.



  $tx = $client->call($operationId => \%params, %content);
  $client = $client->call($operationId => \%params, %content, sub { my ($client, $tx) = @_; });

Used to either call an $operationId that has an "invalid name", such as "list pets" instead of "listPets" or to call an $operationId that you are unsure is supported yet. If it is not, an exception will be thrown, matching text "No such operationId".

$operationId is the name of the resource defined in the OpenAPI specification.

$params is optional, but must be a hash ref, where the keys should match a named parameter in the OpenAPI specification.

%content is used for the body of the request, where the key need to be either "body" or a matching "generators" in Mojo::UserAgent::Transactor. Example:

  $client->addHero({}, body => "Some data");
  $client->addHero({}, json => {name => "Supergirl"});

$tx is a Mojo::Transaction object.


  $promise = $client->call_p($operationId => $params, %content);
  $promise->then(sub { my $tx = shift });

As "call" above, but returns a Mojo::Promise object.


  $client = OpenAPI::Client->new($specification, \%attributes);
  $client = OpenAPI::Client->new($specification, %attributes);

Returns an object of a generated class, with methods generated from the Open API specification located at $specification. See "schema" in JSON::Validator for valid versions of $specification.

Note that the class is cached by perl, so loading a new specification from the same URL will not generate a new class.

Extra %attributes:


  $validator = $client->validator;
  $validator = $class->validator;

Returns a JSON::Validator::Schema::OpenAPIv2 object for a generated class. Note that this is a global variable, so changing the object will affect all instances returned by "new".


Copyright (C) 2017-2021, Jan Henning Thorsen

This program is free software, you can redistribute it and/or modify it under the terms of the Artistic License version 2.0.


Project Founder

Jan Henning Thorsen -


  • Clive Holloway <>

  • Ed J <>

  • Jan Henning Thorsen <>

  • Jan Henning Thorsen <>

  • Mohammad S Anwar <>

  • Reneeb <>

  • Roy Storey <>

  • Veesh Goldman <>