Action Web Service — Serving APIs on rails

Action Web Service provides a way to publish interoperable web service APIs with Rails without spending a lot of time delving into protocol details.

Features

SOAP RPC protocol support
Dynamic WSDL generation for APIs
XML-RPC protocol support
Clients that use the same API definitions as the server for easy interoperability with other Action Web Service based applications
Type signature hints to improve interoperability with static languages
Active Record model class support in signatures

Defining your APIs

You specify the methods you want to make available as API methods in an ActionWebService::API::Base derivative, and then specify this API definition class wherever you want to use that API.

The implementation of the methods is done seperately to the API specification.

Method name inflection

Action Web Service will camelcase the method names according to Rails Inflector rules for the API visible to public callers. What this means, for example is that the method names in generated WSDL will be camelcased, and callers will have to supply the camelcased name in their requests for the request to succeed.

If you do not desire this behaviour, you can turn it off with the ActionWebService::API::Base inflect_names option.

Inflection examples

  :add       => Add
  :find_all  => FindAll

Disabling inflection

  class PersonAPI < ActionWebService::API::Base
    inflect_names false
  end

API definition example

  class PersonAPI < ActionWebService::API::Base
    api_method :add, :expects => [:string, :string, :bool], :returns => [:int]
    api_method :remove, :expects => [:int], :returns => [:bool]
  end

API usage example

  class PersonController < ActionController::Base
    web_service_api PersonAPI

    def add
    end

    def remove
    end
  end

Publishing your APIs

Action Web Service uses Action Pack to process protocol requests. There are two modes of dispatching protocol requests, Direct, and Delegated.

Direct dispatching

This is the default mode. In this mode, controller actions implement the API methods, and parameters for incoming method calls will be placed in @params (keyed by name), and @method_params (ordered list).

The return value of the action is sent back as the return value to the caller.

In this mode, a special api action is generated in the target controller to unwrap the protocol request, forward it on to the relevant action and send back the wrapped return value. This action must not be overridden.

Direct dispatching example

  class PersonController < ApplicationController
    web_service_api PersonAPI

    def add
    end

    def remove
    end
  end

  class PersonAPI < ActionWebService::API::Base
    ...
  end

For this example, protocol requests for Add and Remove methods sent to /person/api will be routed to the actions add and remove.

Delegated dispatching

This mode can be turned on by setting the web_service_dispatching_mode option in a controller to :delegated.

In this mode, the controller contains one or more web service objects (objects that implement an ActionWebService::API::Base definition). These web service objects are each mapped onto one controller action only.

Delegated dispatching example

  class ApiController < ApplicationController
    web_service_dispatching_mode :delegated

    web_service :person, PersonService.new
  end

  class PersonService < ActionWebService::Base
    web_service_api PersonAPI

    def add
    end

    def remove
    end
  end

  class PersonAPI < ActionWebService::API::Base
    ...
  end

For this example, all protocol requests for PersonService are sent to the /api/person action.

The /api/person action is generated when the web_service method is called. This action must not be overridden.

Other controller actions (actions that aren’t the target of a web_service call) are ignored for ActionWebService purposes, and can do normal action tasks.

Layered dispatching

This mode can be turned on by setting the web_service_dispatching_mode option in a controller to :layered.

This mode is similar to delegated mode, in that multiple web service objects can be attached to one controller, however, all protocol requests are sent to a single endpoint.

This mode is only usable by XML-RPC. In this mode, method names can contain prefixes, which will indicate which web service object implements the API identified by that prefix.

The prefix can be any word, followed by a period.

Layered dispatching example

  class ApiController < ApplicationController
    web_service_dispatching_mode :layered

    web_service :mt, MovableTypeService.new
    web_service :blogger, BloggerService.new
    web_service :metaWeblog, MetaWeblogService.new
  end

  class MovableTypeService < ActionWebService::Base
    ...
  end

  class BloggerService < ActionWebService::Base
    ...
  end

  class MetaWeblogService < ActionWebService::API::Base
    ...
  end

For this example, a remote call for a method with a name like mt.getCategories will be dispatched as the getCategories method on the :mt service.

Using the client support

Action Web Service includes client classes that can use the same API definition as the server. The advantage of this approach is that your client will have the same support for Active Record and structured types as the server, and can just use them directly, and rely on the marshaling to Do The Right Thing.

Note: The client support is intended for communication between Ruby on Rails applications that both use Action Web Service. It may work with other servers, but that is not its intended use, and interoperability can’t be guaranteed, especially not for .NET web services.

Web services protocol specifications are complex, and Action Web Service client support can only be guaranteed to work with a subset.

Factory created client example

  class BlogManagerController < ApplicationController
    web_client_api :blogger, :xmlrpc, 'http://url/to/blog/api/RPC2', :handler_name => 'blogger'
  end

  class SearchingController < ApplicationController
    web_client_api :google, :soap, 'http://url/to/blog/api/beta', :service_name => 'GoogleSearch'
  end

See ActionWebService::API::ActionController::ClassMethods for more details.

Manually created client example

  class PersonAPI < ActionWebService::API::Base
    api_method :find_all, :returns => [[Person]]
  end

  soap_client = ActionWebService::Client::Soap.new(PersonAPI, "http://...")
  persons = soap_client.find_all

  class BloggerAPI < ActionWebService::API::Base
    inflect_names false
    api_method :getRecentPosts, :returns => [[Blog::Post]]
  end

  blog = ActionWebService::Client::XmlRpc.new(BloggerAPI, "http://.../xmlrpc", :handler_name => "blogger")
  posts = blog.getRecentPosts

See ActionWebService::Client::Soap and ActionWebService::Client::XmlRpc for more details.

Dependencies

Action Web Service requires that the Action Pack and Active Record are either available to be required immediately or are accessible as GEMs.

It also requires a version of Ruby that includes SOAP support in the standard library. At least version 1.8.2 final (2004-12-25) of Ruby is recommended, this is the version tested against.

Download

The latest Action Web Service version can be downloaded from rubyforge.org/projects/actionservice

Installation

You can install Action Web Service with the following command.

  % [sudo] ruby setup.rb

License

Action Web Service is released under the MIT license.

Support

The Ruby on Rails mailing list

Or, to contact the author, send mail to bitserf@gmail.com

README