JSON:API Serialization Library¶ ↑
:warning: :construction: At the moment, contributions are welcome only for v3! :construction: :warning:¶ ↑
A fast JSON:API serializer for Ruby Objects.
Previously this project was called fast_jsonapi, we forked the project and renamed it to jsonapi/serializer in order to keep it alive.
We would like to thank the Netflix team for the initial work and to all our contributors and users for the continuous support!
Performance Comparison¶ ↑
We compare serialization times with ActiveModelSerializer
and alternative implementations as part of performance tests available at jsonapi-serializer/comparisons.
We want to ensure that with every change on this library, serialization time stays significantly faster than the performance provided by the alternatives. Please read the performance article in the docs
folder for any questions related to methodology.
Table of Contents¶ ↑
Features¶ ↑
-
Declaration syntax similar to Active Model Serializer
-
Support for
belongs_to
,has_many
andhas_one
-
Support for compound documents (included)
-
Optimized serialization of compound documents
-
Caching
Installation¶ ↑
Add this line to your application’s Gemfile:
gem 'jsonapi-serializer'
Execute:
$ bundle install
Usage¶ ↑
Rails Generator¶ ↑
You can use the bundled generator if you are using the library inside of a Rails project:
rails g serializer Movie name year
This will create a new serializer in app/serializers/movie_serializer.rb
Model Definition¶ ↑
class Movie attr_accessor :id, :name, :year, :actor_ids, :owner_id, :movie_type_id end
Serializer Definition¶ ↑
class MovieSerializer include JSONAPI::Serializer set_type :movie # optional set_id :owner_id # optional attributes :name, :year has_many :actors belongs_to :owner, record_type: :user belongs_to :movie_type end
Sample Object
¶ ↑
movie = Movie.new movie.id = 232 movie.name = 'test movie' movie.actor_ids = [1, 2, 3] movie.owner_id = 3 movie.movie_type_id = 1 movie movies = 2.times.map do |i| m = Movie.new m.id = i + 1 m.name = "test movie #{i}" m.actor_ids = [1, 2, 3] m.owner_id = 3 m.movie_type_id = 1 m end
Object
Serialization¶ ↑
Return a hash¶ ↑
hash = MovieSerializer.new(movie).serializable_hash
Return Serialized JSON¶ ↑
json_string = MovieSerializer.new(movie).serializable_hash.to_json
Serialized Output¶ ↑
{ "data": { "id": "3", "type": "movie", "attributes": { "name": "test movie", "year": null }, "relationships": { "actors": { "data": [ { "id": "1", "type": "actor" }, { "id": "2", "type": "actor" } ] }, "owner": { "data": { "id": "3", "type": "user" } } } } }
The Optionality of set_type
¶ ↑
By default fast_jsonapi will try to figure the type based on the name of the serializer class. For example class MovieSerializer
will automatically have a type of :movie
. If your serializer class name does not follow this format, you have to manually state the set_type
at the serializer.
Key Transforms¶ ↑
By default fast_jsonapi underscores the key names. It supports the same key transforms that are supported by AMS. Here is the syntax of specifying a key transform
class MovieSerializer include JSONAPI::Serializer # Available options :camel, :camel_lower, :dash, :underscore(default) set_key_transform :camel end
Here are examples of how these options transform the keys
set_key_transform :camel # "some_key" => "SomeKey" set_key_transform :camel_lower # "some_key" => "someKey" set_key_transform :dash # "some_key" => "some-key" set_key_transform :underscore # "some_key" => "some_key"
Attributes¶ ↑
Attributes are defined using the attributes
method. This method is also aliased as attribute
, which is useful when defining a single attribute.
By default, attributes are read directly from the model property of the same name. In this example, name
is expected to be a property of the object being serialized:
class MovieSerializer include JSONAPI::Serializer attribute :name end
Custom attributes that must be serialized but do not exist on the model can be declared using Ruby block syntax:
class MovieSerializer include JSONAPI::Serializer attributes :name, :year attribute :name_with_year do |object| "#{object.name} (#{object.year})" end end
The block syntax can also be used to override the property on the object:
class MovieSerializer include JSONAPI::Serializer attribute :name do |object| "#{object.name} Part 2" end end
Attributes can also use a different name by passing the original method or accessor with a proc shortcut:
class MovieSerializer include JSONAPI::Serializer attributes :name attribute :released_in_year, &:year end
Links Per Object
¶ ↑
Links are defined using the link
method. By default, links are read directly from the model property of the same name. In this example, public_url
is expected to be a property of the object being serialized.
You can configure the method to use on the object for example a link with key self
will get set to the value returned by a method called url
on the movie object.
You can also use a block to define a url as shown in custom_url
. You can access params in these blocks as well as shown in personalized_url
class MovieSerializer include JSONAPI::Serializer link :public_url link :self, :url link :custom_url do |object| "https://movies.com/#{object.name}-(#{object.year})" end link :personalized_url do |object, params| "https://movies.com/#{object.name}-#{params[:user].reference_code}" end end
Links on a Relationship¶ ↑
You can specify relationship links by using the links:
option on the serializer. Relationship links in JSON API are useful if you want to load a parent document and then load associated documents later due to size constraints (see related resource links)
class MovieSerializer include JSONAPI::Serializer has_many :actors, links: { self: :url, related: -> (object) { "https://movies.com/#{object.id}/actors" } } end
Relationship links can also be configured to be defined as a method on the object.
has_many :actors, links: :actor_relationship_links
This will create a self
reference for the relationship, and a related
link for loading the actors relationship later. NB: This will not automatically disable loading the data in the relationship, you’ll need to do that using the lazy_load_data
option:
has_many :actors, lazy_load_data: true, links: { self: :url, related: -> (object) { "https://movies.com/#{object.id}/actors" } }
Meta Per Resource¶ ↑
For every resource in the collection, you can include a meta object containing non-standard meta-information about a resource that can not be represented as an attribute or relationship.
class MovieSerializer include JSONAPI::Serializer meta do |movie| { years_since_release: Date.current.year - movie.year } end end
Meta on a Relationship¶ ↑
You can specify relationship meta by using the meta:
option on the serializer. Relationship meta in JSON API is useful if you wish to provide non-standard meta-information about the relationship.
Meta can be defined either by passing a static hash or by using Proc to the meta
key. In the latter case, the record and any params passed to the serializer are available inside the Proc as the first and second parameters, respectively.
class MovieSerializer include JSONAPI::Serializer has_many :actors, meta: Proc.new do |movie_record, params| { count: movie_record.actors.length } end end
Compound Document¶ ↑
Support for top-level and nested included associations through options[:include]
.
options = {} options[:meta] = { total: 2 } options[:links] = { self: '...', next: '...', prev: '...' } options[:include] = [:actors, :'actors.agency', :'actors.agency.state'] MovieSerializer.new(movies, options).serializable_hash.to_json
Collection Serialization¶ ↑
options[:meta] = { total: 2 } options[:links] = { self: '...', next: '...', prev: '...' } hash = MovieSerializer.new(movies, options).serializable_hash json_string = MovieSerializer.new(movies, options).serializable_hash.to_json
Control Over Collection Serialization¶ ↑
You can use is_collection
option to have better control over collection serialization.
If this option is not provided or nil
autodetect logic is used to try understand if provided resource is a single object or collection.
Autodetect logic is compatible with most DB toolkits (ActiveRecord, Sequel, etc.) but cannot guarantee that single vs collection will be always detected properly.
options[:is_collection]
was introduced to be able to have precise control this behavior
-
nil
or not provided: will try to autodetect single vs collection (please, see notes above) -
true
will always treat input resource as collection -
false
will always treat input resource as single object
Caching¶ ↑
To enable caching, use cache_options store: <cache_store>
:
class MovieSerializer include JSONAPI::Serializer # use rails cache with a separate namespace and fixed expiry cache_options store: Rails.cache, namespace: 'jsonapi-serializer', expires_in: 1.hour end
store
is required can be anything that implements a #fetch(record, **options, &block)
method:
-
record
is the record that is currently serialized -
options
is everything that was passed tocache_options
exceptstore
, so it can be everyhing the cache store supports -
&block
should be executed to fetch new data if cache is empty
So for the example above it will call the cache instance like this:
Rails.cache.fetch(record, namespace: 'jsonapi-serializer', expires_in: 1.hour) { ... }
Caching and Sparse Fieldsets¶ ↑
If caching is enabled and fields are provided to the serializer, the fieldset will be appended to the cache key’s namespace.
For example, given the following serializer definition and instance:
class ActorSerializer include JSONAPI::Serializer attributes :first_name, :last_name cache_options store: Rails.cache, namespace: 'jsonapi-serializer', expires_in: 1.hour end serializer = ActorSerializer.new(actor, { fields: { actor: [:first_name] } })
The following cache namespace will be generated: 'jsonapi-serializer-fieldset:first_name'
.
Params¶ ↑
In some cases, attribute values might require more information than what is available on the record, for example, access privileges or other information related to a current authenticated user. The options[:params]
value covers these cases by allowing you to pass in a hash of additional parameters necessary for your use case.
Leveraging the new params is easy, when you define a custom id, attribute or relationship with a block you opt-in to using params by adding it as a block parameter.
class MovieSerializer include JSONAPI::Serializer set_id do |movie, params| # in here, params is a hash containing the `:admin` key params[:admin] ? movie.owner_id : "movie-#{movie.id}" end attributes :name, :year attribute :can_view_early do |movie, params| # in here, params is a hash containing the `:current_user` key params[:current_user].is_employee? ? true : false end belongs_to :primary_agent do |movie, params| # in here, params is a hash containing the `:current_user` key params[:current_user] end end # ... current_user = User.find(cookies[:current_user_id]) serializer = MovieSerializer.new(movie, {params: {current_user: current_user}}) serializer.serializable_hash
Custom attributes and relationships that only receive the resource are still possible by defining the block to only receive one argument.
Conditional Attributes¶ ↑
Conditional attributes can be defined by passing a Proc to the if
key on the attribute
method. Return true
if the attribute should be serialized, and false
if not. The record and any params passed to the serializer are available inside the Proc as the first and second parameters, respectively.
class MovieSerializer include JSONAPI::Serializer attributes :name, :year attribute :release_year, if: Proc.new { |record| # Release year will only be serialized if it's greater than 1990 record.release_year > 1990 } attribute :director, if: Proc.new { |record, params| # The director will be serialized only if the :admin key of params is true params && params[:admin] == true } # Custom attribute `name_year` will only be serialized if both `name` and `year` fields are present attribute :name_year, if: Proc.new { |record| record.name.present? && record.year.present? } do |object| "#{object.name} - #{object.year}" end end # ... current_user = User.find(cookies[:current_user_id]) serializer = MovieSerializer.new(movie, { params: { admin: current_user.admin? }}) serializer.serializable_hash
Conditional Relationships¶ ↑
Conditional relationships can be defined by passing a Proc to the if
key. Return true
if the relationship should be serialized, and false
if not. The record and any params passed to the serializer are available inside the Proc as the first and second parameters, respectively.
class MovieSerializer include JSONAPI::Serializer # Actors will only be serialized if the record has any associated actors has_many :actors, if: Proc.new { |record| record.actors.any? } # Owner will only be serialized if the :admin key of params is true belongs_to :owner, if: Proc.new { |record, params| params && params[:admin] == true } end # ... current_user = User.find(cookies[:current_user_id]) serializer = MovieSerializer.new(movie, { params: { admin: current_user.admin? }}) serializer.serializable_hash
Specifying a Relationship Serializer¶ ↑
In many cases, the relationship can automatically detect the serializer to use.
class MovieSerializer include JSONAPI::Serializer # resolves to StudioSerializer belongs_to :studio # resolves to ActorSerializer has_many :actors end
At other times, such as when a property name differs from the class name, you may need to explicitly state the serializer to use. You can do so by specifying a different symbol or the serializer class itself (which is the recommended usage):
class MovieSerializer include JSONAPI::Serializer # resolves to MovieStudioSerializer belongs_to :studio, serializer: :movie_studio # resolves to PerformerSerializer has_many :actors, serializer: PerformerSerializer end
For more advanced cases, such as polymorphic relationships and Single Table Inheritance, you may need even greater control to select the serializer based on the specific object or some specified serialization parameters. You can do by defining the serializer as a Proc
:
class MovieSerializer include JSONAPI::Serializer has_many :actors, serializer: Proc.new do |record, params| if record.comedian? ComedianSerializer elsif params[:use_drama_serializer] DramaSerializer else ActorSerializer end end end
Sparse Fieldsets¶ ↑
Attributes and relationships can be selectively returned per record type by using the fields
option.
class MovieSerializer include JSONAPI::Serializer attributes :name, :year end serializer = MovieSerializer.new(movie, { fields: { movie: [:name] } }) serializer.serializable_hash
Using helper methods¶ ↑
You can mix-in code from another ruby module into your serializer class to reuse functions across your app.
Since a serializer is evaluated in a the context of a class
rather than an instance
of a class, you need to make sure that your methods act as class
methods when mixed in.
Using ActiveSupport::Concern¶ ↑
module AvatarHelper extend ActiveSupport::Concern class_methods do def avatar_url(user) user.image.url end end end class UserSerializer include JSONAPI::Serializer include AvatarHelper # mixes in your helper method as class method set_type :user attributes :name, :email attribute :avatar do |user| avatar_url(user) end end
Using Plain Old Ruby¶ ↑
module AvatarHelper def avatar_url(user) user.image.url end end class UserSerializer include JSONAPI::Serializer extend AvatarHelper # mixes in your helper method as class method set_type :user attributes :name, :email attribute :avatar do |user| avatar_url(user) end end
Customizable Options¶ ↑
Option | Purpose | Example ———— | ————- | ————- set_type | Type name of Object
| set_type :movie
key | Key of Object
| belongs_to :owner, key: :user
set_id | ID of Object
| set_id :owner_id
or set_id { \|record, params\| params[:admin] ? record.id : "#{record.name.downcase}-#{record.id}" }
cache_options | Hash with store to enable caching and optional further cache options | cache_options store: ActiveSupport::Cache::MemoryStore.new, expires_in: 5.minutes
id_method_name | Set custom method name to get ID of an object (If block is provided for the relationship, id_method_name
is invoked on the return value of the block instead of the resource object) | has_many :locations, id_method_name: :place_ids
object_method_name | Set custom method name to get related objects | has_many :locations, object_method_name: :places
record_type | Set custom Object
Type for a relationship | belongs_to :owner, record_type: :user
serializer | Set custom Serializer for a relationship | has_many :actors, serializer: :custom_actor
, has_many :actors, serializer: MyApp::Api::V1::ActorSerializer
, or has_many :actors, serializer -> (object, params) { (return a serializer class) }
polymorphic | Allows different record types for a polymorphic association | has_many :targets, polymorphic: true
polymorphic | Sets custom record types for each object class in a polymorphic association | has_many :targets, polymorphic: { Person => :person, Group => :group }
Performance Instrumentation¶ ↑
Performance instrumentation is available by using the active_support/notifications
.
To enable it, include the module in your serializer class:
require 'jsonapi/serializer' require 'jsonapi/serializer/instrumentation' class MovieSerializer include JSONAPI::Serializer include JSONAPI::Serializer::Instrumentation # ... end
Skylight integration is also available and supported by us, follow the Skylight documentation to enable it.
Running Tests¶ ↑
The project has and requires unit tests, functional tests and performance tests. To run tests use the following command:
rspec
Deserialization¶ ↑
We currently do not support deserialization, but we recommend to use any of the next gems:
JSONAPI.rb¶ ↑
This gem provides the next features alongside deserialization: - Collection meta - Error handling - Includes and sparse fields - Filtering and sorting - Pagination
Migrating from Netflix/fast_jsonapi¶ ↑
If you come from Netflix/fast_jsonapi, here is the instructions to switch.
Modify your Gemfile¶ ↑
- gem 'fast_jsonapi' + gem 'jsonapi-serializer'
Replace all constant references¶ ↑
class MovieSerializer - include FastJsonapi::ObjectSerializer + include JSONAPI::Serializer end
Replace removed methods¶ ↑
- json_string = MovieSerializer.new(movie).serialized_json + json_string = MovieSerializer.new(movie).serializable_hash.to_json
Replace require references¶ ↑
- require 'fast_jsonapi' + require 'jsonapi/serializer'
Update your cache options¶ ↑
See docs.
- cache_options enabled: true, cache_length: 12.hours + cache_options store: Rails.cache, namespace: 'jsonapi-serializer', expires_in: 1.hour
Contributing¶ ↑
Please follow the instructions we provide as part of the issue and pull request creation processes.
This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.