alba

Alba is the fastest JSON serializer for Ruby.


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Alba

Alba is the fastest JSON serializer for Ruby, JRuby an TruffleRuby.

Why Alba?

Because it’s fast, flexible and well-maintained!

Fast

Alba is faster than most of the alternatives. We have a benchmark.

Flexible

Alba provides a small set of DSL to define your serialization logic. It also provides methods you can override to alter and filter serialized hash so that you have full control over the result.

Maintained

Alba is well-maintained and adds features quickly. Coverage Status and CodeClimate Maintainability show the code base is quite healthy.

Installation

Add this line to your application’s Gemfile:

gem 'alba'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install alba

Supported Ruby versions

Alba supports CRuby 2.5.7 and higher and latest JRuby and TruffleRuby.

Documentation

You can find the documentation on RubyDoc.

Features

  • Resource-based serialization
  • Arbitrary attribute definition
  • One and many association with the ability to define them inline
  • Adding condition and filter to association
  • Parameters can be injected and used in attributes and associations
  • Conditional attributes and associations
  • Selectable backend
  • Key transformation
  • Root key inference
  • Error handling
  • Resource name inflection based on association name
  • No runtime dependencies

Anti features

  • Sorting keys
  • Class level support of parameters
  • Supporting all existing JSON encoder/decoder
  • Cache
  • JSON:API support
  • And many others

Usage

Configuration

Alba’s configuration is fairly simple.

Backend configuration

Backend is the actual part serializing an object into JSON. Alba supports these backends.

  • Oj, the fastest. Gem installation required.
  • active_support, mostly for Rails. Gem installation required.
  • default or json, with no external dependencies.

You can set a backend like this:

Alba.backend = :oj

Inference configuration

You can enable inference feature using enable_inference! method.

Alba.enable_inference!

You must install ActiveSupport to enable inference.

Error handling configuration

You can configure error handling with on_error method.

Alba.on_error :ignore

For the details, see Error handling section

Simple serialization with key

class User
  attr_accessor :id, :name, :email, :created_at, :updated_at
  def initialize(id, name, email)
    @id = id
    @name = name
    @email = email
    @created_at = Time.now
    @updated_at = Time.now
  end
end

class UserResource
  include Alba::Resource

  key :user

  attributes :id, :name

  attribute :name_with_email do |resource|
    "#{resource.name}: #{resource.email}"
  end
end

user = User.new(1, 'Masafumi OKURA', 'masafumi@example.com')
UserResource.new(user).serialize
# => "{\"id\":1,\"name\":\"Masafumi OKURA\",\"name_with_email\":\"Masafumi OKURA: masafumi@example.com\"}"

Serialization with associations

class User
  attr_reader :id, :created_at, :updated_at
  attr_accessor :articles

  def initialize(id)
    @id = id
    @created_at = Time.now
    @updated_at = Time.now
    @articles = []
  end
end

class Article
  attr_accessor :user_id, :title, :body

  def initialize(user_id, title, body)
    @user_id = user_id
    @title = title
    @body = body
  end
end

class ArticleResource
  include Alba::Resource

  attributes :title
end

class UserResource
  include Alba::Resource

  attributes :id

  many :articles, resource: ArticleResource
end

user = User.new(1)
article1 = Article.new(1, 'Hello World!', 'Hello World!!!')
user.articles << article1
article2 = Article.new(2, 'Super nice', 'Really nice!')
user.articles << article2

UserResource.new(user).serialize
# => '{"id":1,"articles":[{"title":"Hello World!"},{"title":"Super nice"}]}'

Inline definition with Alba.serialize

Alba.serialize method is a shortcut to define everything inline.

Alba.serialize(user, key: :foo) do
  attributes :id
  many :articles do
    attributes :title, :body
  end
end
# => '{"foo":{"id":1,"articles":[{"title":"Hello World!","body":"Hello World!!!"},{"title":"Super nice","body":"Really nice!"}]}}'

Although this might be useful sometimes, it’s generally recommended to define a class for Resource.

Inheritance and Ignorance

You can exclude or ignore certain attributes using ignoring.

class Foo
  attr_accessor :id, :name, :body

  def initialize(id, name, body)
    @id = id
    @name = name
    @body = body
  end
end

class GenericFooResource
  include Alba::Resource

  attributes :id, :name, :body
end

class RestrictedFooResouce < GenericFooResource
  ignoring :id, :body
end

RestrictedFooResouce.new(foo).serialize
# => '{"name":"my foo"}'
end

Attribute key transformation

** Note: You need to install active_support gem to use transform_keys DSL.

With active_support installed, you can transform attribute keys.

class User
  attr_reader :id, :first_name, :last_name

  def initialize(id, first_name, last_name)
    @id = id
    @first_name = first_name
    @last_name = last_name
  end
end

class UserResource
  include Alba::Resource

  attributes :id, :first_name, :last_name

  transform_keys :lower_camel
end

user = User.new(1, 'Masafumi', 'Okura')
UserResourceCamel.new(user).serialize
# => '{"id":1,"firstName":"Masafumi","lastName":"Okura"}'

Supported transformation types are :camel, :lower_camel and :dash.

Filtering attributes

You can filter attributes by overriding Alba::Resource#converter method, but it’s a bit tricky.

class User
  attr_accessor :id, :name, :email, :created_at, :updated_at

  def initialize(id, name, email)
    @id = id
    @name = name
    @email = email
  end
end

class UserResource
  include Alba::Resource

  attributes :id, :name, :email

  private

  # Here using `Proc#>>` method to compose a proc from `super`
  def converter
    super >> proc { |hash| hash.compact }
  end
end

user = User.new(1, nil, nil)
UserResource.new(user).serialize # => '{"id":1}'

The key part is the use of Proc#>> since Alba::Resource#converter returns a Proc which contains the basic logic and it’s impossible to change its behavior by just overriding the method.

It’s not recommended to swap the whole conversion logic. It’s recommended to always call super when you override converter.

Conditional attributes

Filtering attributes with overriding convert works well for simple cases. However, It’s cumbersome when we want to filter various attributes based on different conditions for keys.

In these cases, conditional attributes works well. We can pass if option to attributes, attribute, one and many. Below is an example for the same effect as filtering attributes section.

class User
  attr_accessor :id, :name, :email, :created_at, :updated_at

  def initialize(id, name, email)
    @id = id
    @name = name
    @email = email
  end
end

class UserResource
  include Alba::Resource

  attributes :id, :name, :email, if: proc { |user, attribute| !attribute.nil? }
end

user = User.new(1, nil, nil)
UserResource.new(user).serialize # => '{"id":1}'

Inference

After Alba.enable_inference! called, Alba tries to infer root key and association resource name.

Alba.enable_inference!

class User
  attr_reader :id
  attr_accessor :articles

  def initialize(id)
    @id = id
    @articles = []
  end
end

class Article
  attr_accessor :id, :title

  def initialize(id, title)
    @id = id
    @title = title
  end
end

class ArticleResource
  include Alba::Resource

  attributes :title
end

class UserResource
  include Alba::Resource

  key!

  attributes :id

  many :articles
end

user = User.new(1)
user.articles << Article.new(1, 'The title')

UserResource.new(user).serialize # => '{"user":{"id":1,"articles":[{"title":"The title"}]}}'
UserResource.new([user]).serialize # => '{"users":[{"id":1,"articles":[{"title":"The title"}]}]}'

This resource automatically sets its root key to either “users” or “user”, depending on the given object is collection or not.

Also, you don’t have to specify which resource class to use with many. Alba infers it from association name.

Note that to enable this feature you must install ActiveSupport gem.

Error handling

You can set error handler globally or per resource using on_error.

class User
  attr_accessor :id, :name

  def initialize(id, name, email)
    @id = id
    @name = name
    @email = email
  end

  def email
    raise RuntimeError, 'Error!'
  end
end

class UserResource
  include Alba::Resource

  attributes :id, :name, :email

  on_error :ignore
end

user = User.new(1, 'Test', 'email@example.com')
UserResource.new(user).serialize # => '{"id":1,"name":"Test"}'

This way you can exclude an entry when fetching an attribute gives an exception.

There are four possible arguments on_error method accepts.

  • :raise re-raises an error. This is the default behavior.
  • :ignore ignores the entry with the error.
  • :nullify sets the attribute with the error to nil.
  • Block gives you more control over what to be returned.

The block receives five arguments, error, object, key, attribute and resource class and must return a two-element array. Below is an example.

# Global error handling
Alba.on_error do |error, object, key, attribute, resource_class|
  if resource_class == MyResource
    ['error_fallback', object.error_fallback]
  else
    [key, error.message]
  end
end

Caching

Currently, Alba doesn’t support caching, primarily due to the behavior of ActiveRecord::Relation’s cache. See the issue.

Comparison

Alba is faster than alternatives. For a performance benchmark, see https://gist.github.com/okuramasafumi/4e375525bd3a28e4ca812d2a3b3e5829.

Rails

When you use Alba in Rails, you can create an initializer file with the line below for compatibility with Rails JSON encoder.

Alba.backend = :active_support

Why named “Alba”?

The name “Alba” comes from “albatross”, a kind of birds. In Japanese, this bird is called “Aho-dori”, which means “stupid bird”. I find it funny because in fact albatrosses fly really fast. I hope Alba looks stupid but in fact it does its job quick.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/okuramasafumi/alba. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Alba project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.