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https://github.com/fotinakis/jsonapi-serializers
Pure Ruby readonly serializers for the JSON:API spec.
https://github.com/fotinakis/jsonapi-serializers
Last synced: 1 day ago
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Pure Ruby readonly serializers for the JSON:API spec.
- Host: GitHub
- URL: https://github.com/fotinakis/jsonapi-serializers
- Owner: fotinakis
- License: mit
- Created: 2015-05-08T22:14:47.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2020-05-27T23:45:12.000Z (over 4 years ago)
- Last Synced: 2024-10-31T13:25:36.465Z (12 days ago)
- Language: Ruby
- Homepage:
- Size: 283 KB
- Stars: 414
- Watchers: 11
- Forks: 91
- Open Issues: 30
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# JSONAPI::Serializers
[](https://travis-ci.org/fotinakis/jsonapi-serializers)
[](http://badge.fury.io/rb/jsonapi-serializers)
JSONAPI::Serializers is a simple library for serializing Ruby objects and their relationships into the [JSON:API format](http://jsonapi.org/format/).
This library is up-to-date with the finalized v1 JSON API spec.
* [Features](#features)
* [Installation](#installation)
* [Usage](#usage)
* [Define a serializer](#define-a-serializer)
* [Serialize an object](#serialize-an-object)
* [Serialize a collection](#serialize-a-collection)
* [Null handling](#null-handling)
* [Multiple attributes](#multiple-attributes)
* [Custom attributes](#custom-attributes)
* [More customizations](#more-customizations)
* [Base URL](#base-url)
* [Root metadata](#root-metadata)
* [Root links](#root-links)
* [Root errors](#root-errors)
* [Root jsonapi object](#root-jsonapi-object)
* [Explicit serializer discovery](#explicit-serializer-discovery)
* [Namespace serializers](#namespace-serializers)
* [Sparse fieldsets](#sparse-fieldsets)
* [Relationships](#relationships)
* [Compound documents and includes](#compound-documents-and-includes)
* [Relationship path handling](#relationship-path-handling)
* [Control links and data in relationships](#control-links-and-data-in-relationships)
* [Instrumentation](#instrumentation)
* [Rails example](#rails-example)
* [Sinatra example](#sinatra-example)
* [Unfinished business](#unfinished-business)
* [Contributing](#contributing)
## Features
* Works with **any Ruby web framework**, including Rails, Sinatra, etc. This is a pure Ruby library.
* Supports the readonly features of the JSON:API spec.
* **Full support for compound documents** ("side-loading") and the `include` parameter.
* Similar interface to ActiveModel::Serializers, should provide an easy migration path.
* Intentionally unopinionated and simple, allows you to structure your app however you would like and then serialize the objects at the end. Easy to integrate with your existing authorization systems and service objects.
JSONAPI::Serializers was built as an intentionally simple serialization interface. It makes no assumptions about your database structure or routes and it does not provide controllers or any create/update interface to the objects. It is a library, not a framework. You will probably still need to do work to make your API fully compliant with the nuances of the [JSON:API spec](http://jsonapi.org/format/), for things like supporting `/relationships` routes and for supporting write actions like creating or updating objects. If you are looking for a more complete and opinionated framework, see the [jsonapi-resources](https://github.com/cerebris/jsonapi-resources) project.
## Installation
Add this line to your application's Gemfile:
```ruby
gem 'jsonapi-serializers'
```
Or install directly with `gem install jsonapi-serializers`.
## Usage
### Define a serializer
```ruby
require 'jsonapi-serializers'
class PostSerializer
include JSONAPI::Serializer
attribute :title
attribute :content
end
```
### Serialize an object
```ruby
JSONAPI::Serializer.serialize(post)
```
Returns a hash:
```json
{
"data": {
"id": "1",
"type": "posts",
"attributes": {
"title": "Hello World",
"content": "Your first post"
},
"links": {
"self": "/posts/1"
}
}
}
```
### Serialize a collection
```ruby
JSONAPI::Serializer.serialize(posts, is_collection: true)
```
Returns:
```json
{
"data": [
{
"id": "1",
"type": "posts",
"attributes": {
"title": "Hello World",
"content": "Your first post"
},
"links": {
"self": "/posts/1"
}
},
{
"id": "2",
"type": "posts",
"attributes": {
"title": "Hello World again",
"content": "Your second post"
},
"links": {
"self": "/posts/2"
}
}
]
}
```
You must always pass `is_collection: true` when serializing a collection, see [Null handling](#null-handling).
### Null handling
```ruby
JSONAPI::Serializer.serialize(nil)
```
Returns:
```json
{
"data": null
}
```
And serializing an empty collection:
```ruby
JSONAPI::Serializer.serialize([], is_collection: true)
```
Returns:
```json
{
"data": []
}
```
Note that the JSON:API spec distinguishes in how null/empty is handled for single objects vs. collections, so you must always provide `is_collection: true` when serializing multiple objects. If you attempt to serialize multiple objects without this flag (or a single object with it on) a `JSONAPI::Serializer::AmbiguousCollectionError` will be raised.
### Multiple attributes
You could declare multiple attributes at once:
```ruby
attributes :title, :body, :contents
```
### Custom attributes
By default the serializer looks for the same name of the attribute on the object it is given. You can customize this behavior by providing a block to `attribute`, `has_one`, or `has_many`:
```ruby
attribute :content do
object.body
end
has_one :comment do
Comment.where(post: object).take!
end
has_many :authors do
Author.where(post: object)
end
```
The block is evaluated within the serializer instance, so it has access to the `object` and `context` instance variables.
### More customizations
Many other formatting and customizations are possible by overriding any of the following instance methods on your serializers.
```ruby
# Override this to customize the JSON:API "id" for this object.
# Always return a string from this method to conform with the JSON:API spec.
def id
object.slug.to_s
end
```
```ruby
# Override this to customize the JSON:API "type" for this object.
# By default, the type is the object's class name lowercased, pluralized, and dasherized,
# per the spec naming recommendations: http://jsonapi.org/recommendations/#naming
# For example, 'MyApp::LongCommment' will become the 'long-comments' type.
def type
'long-comments'
end
```
```ruby
# Override this to customize how attribute names are formatted.
# By default, attribute names are dasherized per the spec naming recommendations:
# http://jsonapi.org/recommendations/#naming
def format_name(attribute_name)
attribute_name.to_s.dasherize
end
```
```ruby
# The opposite of format_name. Override this if you override format_name.
def unformat_name(attribute_name)
attribute_name.to_s.underscore
end
```
```ruby
# Override this to provide resource-object metadata.
# http://jsonapi.org/format/#document-structure-resource-objects
def meta
end
```
```ruby
# Override this to set a base URL (http://example.com) for all links. No trailing slash.
def base_url
@base_url
end
```
```ruby
# Override this to provide a resource-object jsonapi object containing the version in use.
# http://jsonapi.org/format/#document-jsonapi-object
def jsonapi
end
```
```ruby
def self_link
"#{base_url}/#{type}/#{id}"
end
```
```ruby
def relationship_self_link(attribute_name)
"#{self_link}/relationships/#{format_name(attribute_name)}"
end
```
```ruby
def relationship_related_link(attribute_name)
"#{self_link}/#{format_name(attribute_name)}"
end
```
If you override `self_link`, `relationship_self_link`, or `relationship_related_link` to return `nil`, the link will be excluded from the serialized object.
### Base URL
You can override the `base_url` instance method to set a URL to be used in all links.
```ruby
class BaseSerializer
include JSONAPI::Serializer
def base_url
'http://example.com'
end
end
class PostSerializer < BaseSerializer
attribute :title
attribute :content
has_one :author
has_many :comments
end
JSONAPI::Serializer.serialize(post)
```
Returns:
```json
{
"data": {
"id": "1",
"type": "posts",
"attributes": {
"title": "Hello World",
"content": "Your first post"
},
"links": {
"self": "http://example.com/posts/1"
},
"relationships": {
"author": {
"links": {
"self": "http://example.com/posts/1/relationships/author",
"related": "http://example.com/posts/1/author"
}
},
"comments": {
"links": {
"self": "http://example.com/posts/1/relationships/comments",
"related": "http://example.com/posts/1/comments"
},
}
}
}
}
```
Alternatively, you can specify `base_url` as an argument to `serialize` which allows you to build the URL with different subdomains or other logic from the request:
```ruby
JSONAPI::Serializer.serialize(post, base_url: 'http://example.com')
```
Note: if you override `self_link` in your serializer and leave out `base_url`, it will not be included.
### Root metadata
You can pass a `meta` argument to specify top-level metadata:
```ruby
JSONAPI::Serializer.serialize(post, meta: {copyright: 'Copyright 2015 Example Corp.'})
```
### Root links
You can pass a `links` argument to specify top-level links:
```ruby
JSONAPI::Serializer.serialize(post, links: {self: 'https://example.com/posts'})
```
### Root errors
You can use `serialize_errors` method in order to specify top-level errors:
```ruby
errors = [{ "title": "Invalid Attribute", "detail": "First name must contain at least three characters." }]
JSONAPI::Serializer.serialize_errors(errors)
```
If you are using Rails models (ActiveModel by default), you can pass in an object's errors:
```ruby
JSONAPI::Serializer.serialize_errors(user.errors)
```
A more complete usage example (assumes ActiveModel):
```ruby
class Api::V1::ReposController < Api::V1::BaseController
def create
post = Post.create(post_params)
if post.errors
render json: JSONAPI::Serializer.serialize_errors(post.errors)
else
render json: JSONAPI::Serializer.serialize(post)
end
end
end
```
### Root 'jsonapi' object
You can pass a `jsonapi` argument to specify a [top-level "jsonapi" key](http://jsonapi.org/format/#document-jsonapi-object) containing the version of JSON:API in use:
```ruby
JSONAPI::Serializer.serialize(post, jsonapi: {version: '1.0'})
```
### Explicit serializer discovery
By default, jsonapi-serializers assumes that the serializer class for `Namespace::User` is `Namespace::UserSerializer`. You can override this behavior on a per-object basis by implementing the `jsonapi_serializer_class_name` method.
```ruby
class User
def jsonapi_serializer_class_name
'SomeOtherNamespace::CustomUserSerializer'
end
end
```
Now, when a `User` object is serialized, it will use the `SomeOtherNamespace::CustomUserSerializer`.
### Namespace serializers
Assume you have an API with multiple versions:
```ruby
module Api
module V1
class PostSerializer
include JSONAPI::Serializer
attribute :title
end
end
module V2
class PostSerializer
include JSONAPI::Serializer
attribute :name
end
end
end
```
With the namespace option you can choose which serializer is used.
```ruby
JSONAPI::Serializer.serialize(post, namespace: Api::V1)
JSONAPI::Serializer.serialize(post, namespace: Api::V2)
```
This option overrides the `jsonapi_serializer_class_name` method.
### Sparse fieldsets
The JSON:API spec allows to return only [specific fields](http://jsonapi.org/format/#fetching-sparse-fieldsets) from attributes and relationships.
For example, if you wanted to return only the `title` field and `author` relationship link for `posts`:
```ruby
fields =
JSONAPI::Serializer.serialize(post, fields: {posts: [:title]})
```
Sparse fieldsets also affect relationship links. In this case, only the `author` relationship link would be included:
``` ruby
JSONAPI::Serializer.serialize(post, fields: {posts: [:title, :author]})
```
Sparse fieldsets operate on a per-type basis, so they affect all resources in the response including in compound documents. For example, this will affect both the `posts` type in the primary data and the `users` type in the compound data:
``` ruby
JSONAPI::Serializer.serialize(
post,
fields: {posts: ['title', 'author'], users: ['name']},
include: 'author',
)
```
Sparse fieldsets support comma-separated strings (`fields: {posts: 'title,author'}`, arrays of strings (`fields: {posts: ['title', 'author']}`), single symbols (`fields: {posts: :title}`), and arrays of symbols (`fields: {posts: [:title, :author]}`).
## Relationships
You can easily specify relationships with the `has_one` and `has_many` directives.
```ruby
class BaseSerializer
include JSONAPI::Serializer
end
class PostSerializer < BaseSerializer
attribute :title
attribute :content
has_one :author
has_many :comments
end
class UserSerializer < BaseSerializer
attribute :name
end
class CommentSerializer < BaseSerializer
attribute :content
has_one :user
end
```
Note that when serializing a post, the `author` association will come from the `author` attribute on the `Post` instance, no matter what type it is (in this case it is a `User`). This will work just fine, because JSONAPI::Serializers automatically finds serializer classes by appending `Serializer` to the object's class name. This behavior can be customized.
Because the full class name is used when discovering serializers, JSONAPI::Serializers works with any custom namespaces you might have, like a Rails Engine or standard Ruby module namespace.
### Compound documents and includes
> To reduce the number of HTTP requests, servers MAY allow responses that include related resources along with the requested primary resources. Such responses are called "compound documents".
> [JSON:API Compound Documents](http://jsonapi.org/format/#document-structure-compound-documents)
JSONAPI::Serializers supports compound documents with a simple `include` parameter.
For example:
```ruby
JSONAPI::Serializer.serialize(post, include: ['author', 'comments', 'comments.user'])
```
Returns:
```json
{
"data": {
"id": "1",
"type": "posts",
"attributes": {
"title": "Hello World",
"content": "Your first post"
},
"links": {
"self": "/posts/1"
},
"relationships": {
"author": {
"links": {
"self": "/posts/1/relationships/author",
"related": "/posts/1/author"
},
"data": {
"type": "users",
"id": "1"
}
},
"comments": {
"links": {
"self": "/posts/1/relationships/comments",
"related": "/posts/1/comments"
},
"data": [
{
"type": "comments",
"id": "1"
}
]
}
}
},
"included": [
{
"id": "1",
"type": "users",
"attributes": {
"name": "Post Author"
},
"links": {
"self": "/users/1"
}
},
{
"id": "1",
"type": "comments",
"attributes": {
"content": "Have no fear, sers, your king is safe."
},
"links": {
"self": "/comments/1"
},
"relationships": {
"user": {
"links": {
"self": "/comments/1/relationships/user",
"related": "/comments/1/user"
},
"data": {
"type": "users",
"id": "2"
}
},
"post": {
"links": {
"self": "/comments/1/relationships/post",
"related": "/comments/1/post"
}
}
}
},
{
"id": "2",
"type": "users",
"attributes": {
"name": "Barristan Selmy"
},
"links": {
"self": "/users/2"
}
}
]
}
```
Notice a few things:
* The [primary data](http://jsonapi.org/format/#document-structure-top-level) relationships now include "linkage" information for each relationship that was included.
* The related objects themselves are loaded in the top-level `included` member.
* The related objects _also_ include "linkage" data when a deeper relationship is also present in the compound document. This is a very powerful feature of the JSON:API spec, and allows you to deeply link complicated relationships all in the same document and in a single HTTP response. JSONAPI::Serializers automatically includes the correct linkage data for whatever `include` paths you specify. This conforms to this part of the spec:
> Note: Full linkage ensures that included resources are related to either the primary data (which could be resource objects or resource identifier objects) or to each other.
> [JSON:API Compound Documents](http://jsonapi.org/format/#document-compound-documents)
#### Relationship path handling
The `include` param also accepts a string of [relationship paths](http://jsonapi.org/format/#fetching-includes), ie. `include: 'author,comments,comments.user'` so you can pass an `?include` query param directly through to the serialize method. Be aware that letting users pass arbitrary relationship paths might introduce security issues depending on your authorization setup, where a user could `include` a relationship they might not be authorized to see directly. Be aware of what you allow API users to include.
### Control `links` and `data` in relationships
The JSON API spec allows relationships objects to contain `links`, `data`, or both.
By default, `links` are included in each relationship. You can remove links for a specific relationship by passing `include_links: false` to `has_one` or `has_many`. For example:
```ruby
has_many :comments, include_links: false # Default is include_links: true.
```
Notice that `links` are now excluded for the `comments` relationship:
```json
"relationships": {
"author": {
"links": {
"self": "/posts/1/relationships/author",
"related": "/posts/1/author"
}
},
"comments": {}
}
```
By default, `data` is excluded in each relationship. You can enable data for a specific relationship by passing `include_data: true` to `has_one` or `has_many`. For example:
```ruby
has_one :author, include_data: true # Default is include_data: false.
```
Notice that linkage data is now included for the `author` relationship:
```json
"relationships": {
"author": {
"links": {
"self": "/posts/1/relationships/author",
"related": "/posts/1/author"
},
"data": {
"type": "users",
"id": "1"
}
}
```
## Instrumentation
Using [ActiveSupport::Notifications](https://api.rubyonrails.org/classes/ActiveSupport/Notifications.html) you can subscribe to key notifications to better understand the performance of your serialization.
The following notifications can be subscribed to:
* `render.jsonapi_serializers.serialize_primary` - time spent serializing a single object
* `render.jsonapi_serializers.find_recursive_relationships` - time spent finding objects to serialize through relationships
This is an example of how you might subscribe to all events that come from `jsonapi-serializers`.
```ruby
require 'active_support/notifications'
ActiveSupport::Notifications.subscribe(/^render\.jsonapi_serializers\..*/) do |*args|
event = ActiveSupport::Notifications::Event.new(*args)
puts event.name
puts event.time
puts event.end
puts event.payload
end
```
## Rails example
```ruby
# app/serializers/base_serializer.rb
class BaseSerializer
include JSONAPI::Serializer
def self_link
"/api/v1#{super}"
end
end
# app/serializers/post_serializer.rb
class PostSerializer < BaseSerializer
attribute :title
attribute :content
end
# app/controllers/api/v1/base_controller.rb
class Api::V1::BaseController < ActionController::Base
# Convenience methods for serializing models:
def serialize_model(model, options = {})
options[:is_collection] = false
JSONAPI::Serializer.serialize(model, options)
end
def serialize_models(models, options = {})
options[:is_collection] = true
JSONAPI::Serializer.serialize(models, options)
end
end
# app/controllers/api/v1/posts_controller.rb
class Api::V1::ReposController < Api::V1::BaseController
def index
posts = Post.all
render json: serialize_models(posts)
end
def show
post = Post.find(params[:id])
render json: serialize_model(post)
end
end
# config/initializers/jsonapi_mimetypes.rb
# Without this mimetype registration, controllers will not automatically parse JSON API params.
# Rails 4
module JSONAPI
MIMETYPE = "application/vnd.api+json"
end
Mime::Type.register(JSONAPI::MIMETYPE, :api_json)
ActionDispatch::ParamsParser::DEFAULT_PARSERS[Mime::Type.lookup(JSONAPI::MIMETYPE)] = lambda do |body|
JSON.parse(body)
end
# Rails 5 Option 1: Add another synonym to the json mime type
json_mime_type_synonyms = %w[
text/x-json
application/jsonrequest
application/vnd.api+json
]
Mime::Type.register('application/json', :json, json_mime_type_synonyms)
# Rails 5 Option 2: Add a separate mime type
Mime::Type.register('application/vnd.api+json', :api_json)
ActionDispatch::Request.parameter_parsers[:api_json] = -> (body) {
JSON.parse(body)
}
```
## Sinatra example
Here's an example using [Sinatra](http://www.sinatrarb.com) and
[Sequel ORM](http://sequel.jeremyevans.net) instead of Rails and ActiveRecord.
The important takeaways here are that:
1. The `:tactical_eager_loading` plugin will greatly reduce the number of
queries performed when sideloading associated records. You can add this
plugin to a single model (as demonstrated here), or globally to all models.
For more information, please see the Sequel
[documentation](http://sequel.jeremyevans.net/rdoc-plugins/classes/Sequel/Plugins/TacticalEagerLoading.html).
1. The `:skip_collection_check` option must be set to true in order for
JSONAPI::Serializer to be able to serialize a single Sequel::Model instance.
1. You should call `#all` on your Sequel::Dataset instances before passing them
to JSONAPI::Serializer to greatly reduce the number of queries performed.
```ruby
require 'sequel'
require 'sinatra/base'
require 'json'
require 'jsonapi-serializers'
class Post < Sequel::Model
plugin :tactical_eager_loading
one_to_many :comments
end
class Comment < Sequel::Model
many_to_one :post
end
class BaseSerializer
include JSONAPI::Serializer
def self_link
"/api/v1#{super}"
end
end
class PostSerializer < BaseSerializer
attributes :title, :content
has_many :comments
end
class CommentSerializer < BaseSerializer
attributes :username, :content
has_one :post
end
module Api
class V1 < Sinatra::Base
configure do
mime_type :api_json, 'application/vnd.api+json'
set :database, Sequel.connect
end
helpers do
def parse_request_body
return unless request.body.respond_to?(:size) &&
request.body.size > 0
halt 415 unless request.content_type &&
request.content_type[/^[^;]+/] == mime_type(:api_json)
request.body.rewind
JSON.parse(request.body.read, symbolize_names: true)
end
# Convenience methods for serializing models:
def serialize_model(model, options = {})
options[:is_collection] = false
options[:skip_collection_check] = true
JSONAPI::Serializer.serialize(model, options)
end
def serialize_models(models, options = {})
options[:is_collection] = true
JSONAPI::Serializer.serialize(models, options)
end
end
before do
halt 406 unless request.preferred_type.entry == mime_type(:api_json)
@data = parse_request_body
content_type :api_json
end
get '/posts' do
posts = Post.all
serialize_models(posts).to_json
end
get '/posts/:id' do
post = Post[params[:id].to_i]
not_found if post.nil?
serialize_model(post, include: 'comments').to_json
end
end
end
```
See also: [Sinja](https://github.com/mwpastore/sinja), which extends Sinatra
and leverages jsonapi-serializers to provide a JSON:API framework.
## Changelog
See [Releases](https://github.com/fotinakis/jsonapi-serializers/releases).
## Unfinished business
* Support for pagination/sorting is unlikely to be supported because it would likely involve coupling to ActiveRecord, but please open an issue if you have ideas of how to support this generically.
## Contributing
1. Fork it ( https://github.com/fotinakis/jsonapi-serializers/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request
Throw a ★ on it! :)