JSONAPI::Resources
, or "JR", provides a framework for developing a server that complies with the
JSON API specification.
Like JSON API itself, JR's design is focused on the resources served by an API. JR needs little more than a definition of your resources, including their attributes and relationships, to make your server compliant with JSON API.
JR is designed to work with Rails 4.0+, and provides custom routes, controllers, and serializers. JR's resources may be backed by ActiveRecord models or by custom objects.
Table of Contents
- [Demo App] (#demo-app)
- [Client Libraries] (#client-libraries)
- [Installation] (#installation)
- [Usage] (#usage)
- [Resources] (#resources)
- [JSONAPI::Resource] (#jsonapiresource)
- [Attributes] (#attributes)
- [Primary Key] (#primary-key)
- [Model Name] (#model-name)
- [Relationships] (#relationships)
- [Filters] (#filters)
- [Pagination] (#pagination)
- [Included relationships (side-loading resources)] (#included-relationships-side-loading-resources)
- [Callbacks] (#callbacks)
- [Controllers] (#controllers)
- [Namespaces] (#namespaces)
- [Error Codes] (#error-codes)
- [Handling Exceptions] (#handling-exceptions)
- [Action Callbacks] (#action-callbacks)
- [Serializer] (#serializer)
- [Resources] (#resources)
- [Configuration] (#configuration)
- [Contributing] (#contributing)
- [License] (#license)
Demo App
We have a simple demo app, called Peeps, available to show how JR is used.
Client Libraries
JSON API maintains a (non-verified) listing of client libraries which should be compatible with JSON API compliant server implementations such as JR.
Installation
Add JR to your application's Gemfile
:
gem 'jsonapi-resources'
And then execute:
$ bundle
Or install it yourself as:
$ gem install jsonapi-resources
Usage
Resources
Resources define the public interface to your API. A resource defines which attributes are exposed, as well as relationships to other resources.
Resource definitions should by convention be placed in a directory under app named resources, app/resources
. The class
name should be the single underscored name of the model that backs the resource with _resource.rb
appended. For example,
a Contact
model's resource should have a class named ContactResource
defined in a file named contact_resource.rb
.
JSONAPI::Resource
Resources must be derived from JSONAPI::Resource
, or a class that is itself derived from JSONAPI::Resource
.
For example:
class ContactResource < JSONAPI::Resource
end
A jsonapi-resource generator is avaliable
rails generate jsonapi:resource contact
Abstract Resources
Resources that are not backed by a model (purely used as base classes for other resources) should be declared as abstract.
Because abstract resources do not expect to be backed by a model, they won't attempt to discover the model class or any of its relationships.
class BaseResource < JSONAPI::Resource
abstract
has_one :creator
end
class ContactResource < BaseResource
end
Attributes
Any of a resource's attributes that are accessible must be explicitly declared. Single attributes can be declared using
the attribute
method, and multiple attributes can be declared with the attributes
method on the resource class.
For example:
class ContactResource < JSONAPI::Resource
attribute :name_first
attributes :name_last, :email, :twitter
end
This resource has 4 defined attributes: name_first
, name_last
, email
, twitter
, as well as the automatically
defined attributes id
and type
. By default these attributes must exist on the model that is handled by the resource.
A resource object wraps a Ruby object, usually an ActiveModel
record, which is available as the @model
variable.
This allows a resource's methods to access the underlying model.
For example, a computed attribute for full_name
could be defined as such:
class ContactResource < JSONAPI::Resource
attributes :name_first, :name_last, :email, :twitter
attribute :full_name
def full_name
"#{@model.name_first}, #{@model.name_last}"
end
end
Fetchable Attributes
By default all attributes are assumed to be fetchable. The list of fetchable attributes can be filtered by overriding
the fetchable_fields
method.
Here's an example that prevents guest users from seeing the email
field:
class AuthorResource < JSONAPI::Resource
attributes :name, :email
model_name 'Person'
has_many :posts
def fetchable_fields
if (context[:current_user].guest)
super - [:email]
else
super
end
end
end
Context flows through from the controller to the resource and can be used to control the attributes based on the current user (or other value).
Creatable and Updatable Attributes
By default all attributes are assumed to be updatable and creatable. To prevent some attributes from being accepted by
the update
or create
methods, override the self.updatable_fields
and self.creatable_fields
methods on a resource.
This example prevents full_name
from being set:
class ContactResource < JSONAPI::Resource
attributes :name_first, :name_last, :full_name
def full_name
"#{@model.name_first}, #{@model.name_last}"
end
def self.updatable_fields(context)
super - [:full_name]
end
def self.creatable_fields(context)
super - [:full_name]
end
end
The context
is not by default used by the ResourceController
, but may be used if you override the controller methods.
By using the context you have the option to determine the creatable and updatable fields based on the user.
Sortable Attributes
JR supports sorting primary resources by multiple sort criteria.
By default all attributes are assumed to be sortable. To prevent some attributes from being sortable, override the
self.sortable_fields
method on a resource.
Here's an example that prevents sorting by post's body
:
class PostResource < JSONAPI::Resource
attributes :title, :body
def self.sortable_fields(context)
super(context) - [:body]
end
end
Attribute Formatting
Attributes can have a Format
. By default all attributes use the default formatter. If an attribute has the format
option set the system will attempt to find a formatter based on this name. In the following example the last_login_time
will be returned formatted to a certain time zone:
class PersonResource < JSONAPI::Resource
attributes :name, :email
attribute :last_login_time, format: :date_with_timezone
end
The system will lookup a value formatter named DateWithTimezoneValueFormatter
and will use this when serializing and
updating the attribute. See the Value Formatters section for more details.
Flattening a Rails relationship
It is possible to flatten Rails relationships into attributes by using getters and setters. This can become handy if a relation needs to be created alongside the creation of the main object which can be the case if there is a bi-directional presence validation. For example:
# Given Models
class Person < ActiveRecord::Base
has_many :spoken_languages
validates :name, :email, :spoken_languages, presence: true
end
class SpokenLanguage < ActiveRecord::Base
belongs_to :person, inverse_of: :spoken_languages
validates :person, :language_code, presence: true
end
# Resource with getters and setter
class PersonResource < JSONAPI::Resource
attributes :name, :email, :spoken_languages
# Getter
def spoken_languages
@model.spoken_languages.pluck(:language_code)
end
# Setter (because spoken_languages needed for creation)
def spoken_languages=(new_spoken_language_codes)
@model.spoken_languages.destroy_all
new_spoken_language_codes.each do |new_lang_code|
@model.spoken_languages.build(language_code: new_lang_code)
end
end
end
Primary Key
Resources are always represented using a key of id
. The resource will interrogate the model to find the primary key.
If the underlying model does not use id
as the primary key and does not support the primary_key
method you
must use the primary_key
method to tell the resource which field on the model to use as the primary key. Note:
this must be the actual primary key of the model.
By default only integer values are allowed for primary key. To change this behavior you can set the resource_key_type
configuration option:
JSONAPI.configure do |config|
# Allowed values are :integer(default), :uuid, :string, or a proc
config.resource_key_type = :uuid
end
Override key type on a resource
You can override the default resource key type on a per-resource basis by calling key_type
in the resource class,
with the same allowed values as the resource_key_type
configuration option.
class ContactResource < JSONAPI::Resource
attribute :id
attributes :name_first, :name_last, :email, :twitter
key_type :uuid
end
Custom resource key validators
If you need more control over the key, you can override the #verify_key method on your resource, or set a lambda that accepts key and context arguments in config/initializers/jsonapi_resources.rb
:
JSONAPI.configure do |config|
config.resource_key_type = -> (key, context) { key && String(key) }
end
Model Name
The name of the underlying model is inferred from the Resource name. It can be overridden by use of the model_name
method. For example:
class AuthorResource < JSONAPI::Resource
attribute :name
model_name 'Person'
has_many :posts
end
Relationships
Related resources need to be specified in the resource. These may be declared with the relationship
or the has_one
and the has_many
methods.
Here's a simple example using the relationship
method where a post has a single author and an author can have many
posts:
class PostResource < JSONAPI::Resource
attribute :title, :body
relationship :author, to: :one
end
And the corresponding author:
class AuthorResource < JSONAPI::Resource
attribute :name
relationship :posts, to: :many
end
And here's the equivalent resources using the has_one
and has_many
methods:
class PostResource < JSONAPI::Resource
attribute :title, :body
has_one :author
end
And the corresponding author:
class AuthorResource < JSONAPI::Resource
attribute :name
has_many :posts
end
Options
The relationship methods (relationship
, has_one
, and has_many
) support the following options:
class_name
- a string specifying the underlying class for the related resource. Defaults to theclass_name
property on the underlying model.foreign_key
- the method on the resource used to fetch the related resource. Defaults to<resource_name>_id
for has_one and<resource_name>_ids
for has_many relationships.acts_as_set
- allows the entire set of related records to be replaced in one operation. Defaults to false if not set.polymorphic
- set to true to identify relationships that are polymorphic.relation_name
- the name of the relation to use on the model. A lambda may be provided which allows conditional selection of the relation based on the context.
to_one
relationships support the additional option:
foreign_key_on
- defaults to:self
. To indicate that the foreign key is on the related resource specify:related
.
Examples:
class CommentResource < JSONAPI::Resource
attributes :body
has_one :post
has_one :author, class_name: 'Person'
has_many :tags, acts_as_set: true
end
class ExpenseEntryResource < JSONAPI::Resource
attributes :cost, :transaction_date
has_one :currency, class_name: 'Currency', foreign_key: 'currency_code'
has_one :employee
end
class TagResource < JSONAPI::Resource
attributes :name
has_one :taggable, polymorphic: true
end
class BookResource < JSONAPI::Resource
# Only book_admins may see unapproved comments for a book. Using
# a lambda to select the correct relation on the model
has_many :book_comments, relation_name: -> (options = {}) {
context = options[:context]
current_user = context ? context[:current_user] : nil
unless current_user && current_user.book_admin
:approved_book_comments
else
:book_comments
end
}
...
end
The polymorphic relationship will require the resource and controller to exist, although routing to them will cause an error.
class TaggableResource < JSONAPI::Resource; end
class TaggablesController < JSONAPI::ResourceController; end
Filters
Filters for locating objects of the resource type are specified in the resource definition. Single filters can be
declared using the filter
method, and multiple filters can be declared with the filters
method on the resource
class.
For example:
class ContactResource < JSONAPI::Resource
attributes :name_first, :name_last, :email, :twitter
filter :id
filters :name_first, :name_last
end
Then a request could pass in a filter for example http://example.com/contacts?filter[name_last]=Smith
and the system
will find all people where the last name exactly matches Smith.
Default Filters
A default filter may be defined for a resource using the default
option on the filter
method. This default is used
unless the request overrides this value.
For example:
class CommentResource < JSONAPI::Resource
attributes :body, :status
has_one :post
has_one :author
filter :status, default: 'published,pending'
end
The default value is used as if it came from the request.
Finders
Basic finding by filters is supported by resources. This is implemented in the find
and find_by_key
finder methods.
Currently this is implemented for ActiveRecord
based resources. The finder methods rely on the records
method to get
an Arel
relation. It is therefore possible to override records
to affect the three find related methods.
Customizing base records for finder methods
If you need to change the base records on which find
and find_by_key
operate, you can override the records
method
on the resource class.
For example to allow a user to only retrieve his own posts you can do the following:
class PostResource < JSONAPI::Resource
attribute :title, :body
def self.records(options = {})
context = options[:context]
context[:current_user].posts
end
end
When you create a relationship, a method is created to fetch record(s) for that relationship, using the relation name for the relationship.
class PostResource < JSONAPI::Resource
has_one :author
has_many :comments
# def record_for_author
# relation_name = relationship.relation_name(context: @context)
# records_for(relation_name)
# end
# def records_for_comments
# relation_name = relationship.relation_name(context: @context)
# records_for(relation_name)
# end
end
For example, you may want raise an error if the user is not authorized to view the related records. See the next section for additional details on raising errors.
class BaseResource < JSONAPI::Resource
def records_for(relation_name)
context = options[:context]
records = model.public_send(relation_name)
unless context[:current_user].can_view?(records)
raise NotAuthorizedError
end
records
end
end
Raising Errors
Inside the finder methods (like records_for
) or inside of resource callbacks
(like before_save
) you can raise
an error to halt processing. JSONAPI::Resources
has some built in errors that will return appropriate error codes. By
default any other error that you raise will return a 500
status code
for a general internal server error.
To return useful error codes that represent application errors you
should set the exception_class_whitelist
config varible, and then you
should use the Rails rescue_from
macro to render a status code.
For example, this config setting allows the NotAuthorizedError
to bubble up out of
JSONAPI::Resources and into your application.
# config/initializer/jsonapi-resources.rb
JSONAPI.configure do |config|
config.exception_class_whitelist = [NotAuthorizedError]
end
Handling the error and rendering the appropriate code is now the resonsiblity of the application and could be handled like this:
class ApiController < ApplicationController
rescue_from NotAuthorizedError, with: :reject_forbidden_request
def reject_forbidden_request
render json: {error: 'Forbidden'}, :status => 403
end
end
Applying Filters
The apply_filter
method is called to apply each filter to the Arel
relation. You may override this method to gain
control over how the filters are applied to the Arel
relation.
This example shows how you can implement different approaches for different filters.
def self.apply_filter(records, filter, value, options)
case filter
when :visibility
records.where('users.publicly_visible = ?', value == :public)
when :last_name, :first_name, :name
if value.is_a?(Array)
value.each do |val|
records = records.where(_model_class.arel_table[filter].matches(val))
end
return records
else
records.where(_model_class.arel_table[filter].matches(value))
end
else
return super(records, filter, value)
end
end
Override finder methods
Finally if you have more complex requirements for finding you can override the find
and find_by_key
methods on the
resource class.
Here's an example that defers the find
operation to a current_user
set on the context
option:
class AuthorResource < JSONAPI::Resource
attribute :name
model_name 'Person'
has_many :posts
filter :name
def self.find(filters, options = {})
context = options[:context]
authors = context[:current_user].find_authors(filters)
return authors.map do |author|
self.new(author, context)
end
end
end
Pagination
Pagination is performed using a paginator
, which is a class responsible for parsing the page
request parameters and
applying the pagination logic to the results.
Paginators
JSONAPI::Resource
supports several pagination methods by default, and allows you to implement a custom system if the
defaults do not meet your needs.
Paged Paginator
The paged
paginator
returns results based on pages of a fixed size. Valid page
parameters are number
and size
.
If number
is omitted the first page is returned. If size
is omitted the default_page_size
from the configuration
settings is used.
Offset Paginator
The offset
paginator
returns results based on an offset from the beginning of the resultset. Valid page
parameters
are offset
and limit
. If offset
is omitted a value of 0 will be used. If limit
is omitted the default_page_size
from the configuration settings is used.
Custom Paginators
Custom paginators
can be used. These should derive from Paginator
. The apply
method takes a relation
and
order_options
and is expected to return a relation
. The initialize
method receives the parameters from the page
request parameters. It is up to the paginator author to parse and validate these parameters.
For example, here is a very simple single record at a time paginator:
class SingleRecordPaginator < JSONAPI::Paginator
def initialize(params)
# param parsing and validation here
@page = params.to_i
end
def apply(relation, order_options)
relation.offset(@page).limit(1)
end
end
Paginator Configuration
The default paginator, which will be used for all resources, is set using JSONAPI.configure
. For example, in your
config/initializers/jsonapi_resources.rb
:
JSONAPI.configure do |config|
# built in paginators are :none, :offset, :paged
config.default_paginator = :offset
config.default_page_size = 10
config.maximum_page_size = 20
end
If no default_paginator
is configured, pagination will be disabled by default.
Paginators can also be set at the resource-level, which will override the default setting. This is done using the
paginator
method:
class BookResource < JSONAPI::Resource
attribute :title
attribute :isbn
paginator :offset
end
To disable pagination in a resource, specify :none
for paginator
.
Included relationships (side-loading resources)
JR supports request include params out of the box, for side loading related resources.
Here's an example from the spec:
GET /articles/1?include=comments HTTP/1.1
Accept: application/vnd.api+json
Will get you the following payload by default:
{
"data": {
"type": "articles",
"id": "1",
"attributes": {
"title": "JSON API paints my bikeshed!"
},
"links": {
"self": "http://example.com/articles/1"
},
"relationships": {
"comments": {
"links": {
"self": "http://example.com/articles/1/relationships/comments",
"related": "http://example.com/articles/1/comments"
},
"data": [
{ "type": "comments", "id": "5" },
{ "type": "comments", "id": "12" }
]
}
}
},
"included": [{
"type": "comments",
"id": "5",
"attributes": {
"body": "First!"
},
"links": {
"self": "http://example.com/comments/5"
}
}, {
"type": "comments",
"id": "12",
"attributes": {
"body": "I like XML better"
},
"links": {
"self": "http://example.com/comments/12"
}
}]
}
Callbacks
ActiveSupport::Callbacks
is used to provide callback functionality, so the behavior is very similar to what you may be
used to from ActiveRecord
.
For example, you might use a callback to perform authorization on your resource before an action.
class BaseResource < JSONAPI::Resource
before_create :authorize_create
def authorize_create
# ...
end
end
The types of supported callbacks are:
before
after
around
JSONAPI::Resource
Callbacks
Callbacks can be defined for the following JSONAPI::Resource
events:
:create
:update
:remove
:save
:create_has_many_link
:replace_has_many_links
:create_has_one_link
:replace_has_one_link
:remove_has_many_link
:remove_has_one_link
:replace_fields
JSONAPI::OperationsProcessor
Callbacks
Callbacks can also be defined for JSONAPI::OperationsProcessor
events:
:operations
: The set of operations.:operation
: Any individual operation.:find_operation
: Afind_operation
.:show_operation
: Ashow_operation
.:show_relationship_operation
: Ashow_relationship_operation
.:show_related_resource_operation
: Ashow_related_resource_operation
.:show_related_resources_operation
: Ashow_related_resources_operation
.:create_resource_operation
: Acreate_resource_operation
.:remove_resource_operation
: Aremove_resource_operation
.:replace_fields_operation
: Areplace_fields_operation
.:replace_has_one_relationship_operation
: Areplace_has_one_relationship_operation
.:create_has_many_relationship_operation
: Acreate_has_many_relationship_operation
.:replace_has_many_relationship_operation
: Areplace_has_many_relationship_operation
.:remove_has_many_relationship_operation
: Aremove_has_many_relationship_operation
.:remove_has_one_relationship_operation
: Aremove_has_one_relationship_operation
.
The operation callbacks have access to two meta data hashes, @operations_meta
and @operation_meta
, two links hashes,
@operations_links
and @operation_links
, the full list of @operations
, each individual @operation
and the
@result
variables.
OperationsProcessor
Example to Return total_count in Meta
Custom Note: this can also be accomplished with the top_level_meta_include_record_count
option, and in most cases that will
be the better option.
To return the total record count of a find operation in the meta data of a find operation you can create a custom OperationsProcessor. For example:
# lib/jsonapi/counting_active_record_operations_processor.rb
class CountingActiveRecordOperationsProcessor < ActiveRecordOperationsProcessor
after_find_operation do
@operation_meta[:total_records] = @operation.record_count
end
end
Set the configuration option operations_processor
to use the new CountingActiveRecordOperationsProcessor
by
specifying the snake cased name of the class (without the OperationsProcessor
).
require 'jsonapi/counting_active_record_operations_processor'
JSONAPI.configure do |config|
config.operations_processor = :counting_active_record
end
The callback code will be called after each find. It will use the same options as the find operation, without the
pagination, to collect the record count. This is stored in the operation_meta
, which will be returned in the top level
meta element.
Controllers
There are two ways to implement a controller for your resources. Either derive from ResourceController
or import
the ActsAsResourceController
module.
ResourceController
JSONAPI::Resources
provides a class, ResourceController
, that can be used as the base class for your controllers.
ResourceController
supports index
, show
, create
, update
, and destroy
methods. Just deriving your controller
from ResourceController
will give you a fully functional controller.
For example:
class PeopleController < JSONAPI::ResourceController
end
Of course you are free to extend this as needed and override action handlers or other methods.
The context that's used for serialization and resource configuration is set by the controller's context
method.
For example:
class ApplicationController < JSONAPI::ResourceController
def context
{current_user: current_user}
end
end
# Specific resource controllers derive from ApplicationController
# and share its context
class PeopleController < ApplicationController
end
Note: This gem uses the filter chain to set up the request. In some instances, variables that are set in the filter chain (such as
current_user
) may not be set at the right time. If this happens (i.e.current_user
isnil
incontext
but it's set properly everywhere else), you may want to have your authentication occur earlier in the filter chain, usingprepend_before_action
instead ofbefore_action
.
ActsAsResourceController
JSONAPI::Resources
also provides a module, JSONAPI::ActsAsResourceController
. You can include this module to
mix in all the features of ResourceController
into your existing controller class.
For example:
class PostsController < ActionController::Base
include JSONAPI::ActsAsResourceController
end
Namespaces
JSONAPI::Resources supports namespacing of controllers and resources. With namespacing you can version your API.
If you namespace your controller it will require a namespaced resource.
In the following example we have a resource
that isn't namespaced, and one the has now been namespaced. There are
slight differences between the two resources, as might be seen in a new version of an API:
class PostResource < JSONAPI::Resource
attribute :title
attribute :body
attribute :subject
has_one :author, class_name: 'Person'
has_one :section
has_many :tags, acts_as_set: true
has_many :comments, acts_as_set: false
def subject
@model.title
end
filters :title, :author, :tags, :comments
filter :id
end
...
module Api
module V1
class PostResource < JSONAPI::Resource
# V1 replaces the non-namespaced resource
# V1 no longer supports tags and now calls author 'writer'
attribute :title
attribute :body
attribute :subject
has_one :writer, foreign_key: 'author_id'
has_one :section
has_many :comments, acts_as_set: false
def subject
@model.title
end
filters :writer
end
class WriterResource < JSONAPI::Resource
attributes :name, :email
model_name 'Person'
has_many :posts
filter :name
end
end
end
The following controllers are used:
class PostsController < JSONAPI::ResourceController
end
module Api
module V1
class PostsController < JSONAPI::ResourceController
end
end
end
You will also need to namespace your routes:
Rails.application.routes.draw do
jsonapi_resources :posts
namespace :api do
namespace :v1 do
jsonapi_resources :posts
end
end
end
When a namespaced resource
is used, any related resources
must also be in the same namespace.
Error codes
Error codes are provided for each error object returned, based on the error. These errors are:
module JSONAPI
VALIDATION_ERROR = 100
INVALID_RESOURCE = 101
FILTER_NOT_ALLOWED = 102
INVALID_FIELD_VALUE = 103
INVALID_FIELD = 104
PARAM_NOT_ALLOWED = 105
PARAM_MISSING = 106
INVALID_FILTER_VALUE = 107
COUNT_MISMATCH = 108
KEY_ORDER_MISMATCH = 109
KEY_NOT_INCLUDED_IN_URL = 110
INVALID_INCLUDE = 112
RELATION_EXISTS = 113
INVALID_SORT_CRITERIA = 114
INVALID_LINKS_OBJECT = 115
TYPE_MISMATCH = 116
INVALID_PAGE_OBJECT = 117
INVALID_PAGE_VALUE = 118
INVALID_FIELD_FORMAT = 119
INVALID_FILTERS_SYNTAX = 120
SAVE_FAILED = 121
FORBIDDEN = 403
RECORD_NOT_FOUND = 404
UNSUPPORTED_MEDIA_TYPE = 415
LOCKED = 423
end
These codes can be customized in your app by creating an initializer to override any or all of the codes.
In addition textual error codes can be returned by setting the configuration option use_text_errors = true
. For
example:
JSONAPI.configure do |config|
config.use_text_errors = true
end
Handling Exceptions
By default, all exceptions raised downstream from a resource controller will be caught, logged, and a 500 Internal Server Error
will be rendered. Exceptions can be whitelisted in the config to pass through the handler and be caught manually, or you can pass a callback from a resource controller to insert logic into the rescue block without interrupting the control flow. This can be particularly useful for additional logging or monitoring without the added work of rendering responses.
Pass a block, refer to controller class methods, or both. Note that methods must be defined as class methods on a controller and accept one parameter, which is passed the exception object that was rescued.
class ApplicationController < JSONAPI::ResourceController
on_server_error :first_callback
#or
# on_server_error do |error|
#do things
#end
def self.first_callback(error)
#env["airbrake.error_id"] = notify_airbrake(error)
end
end
Action Callbacks
ensure_correct_media_type
By default, when controllers extend functionalities from jsonapi-resources
, the ActsAsResourceController#ensure_correct_media_type
method will be triggered before create
, update
, create_relationship
and update_relationship
actions. This method is reponsible
for checking if client's request corresponds to the correct media type required by JSON API: application/vnd.api+json
.
In case you need to check the media type for custom actions, just make sure to call the method in your controller's before_action
:
class UsersController < JSONAPI::ResourceController
before_action :ensure_correct_media_type, only: [:auth]
def auth
# some crazy auth code goes here
end
end
Serializer
The ResourceSerializer
can be used to serialize a resource into JSON API compliant JSON. ResourceSerializer
must be
initialized with the primary resource type it will be serializing. ResourceSerializer
has a serialize_to_hash
method that takes a resource instance or array of resource instances to serialize. For example:
post = Post.find(1)
JSONAPI::ResourceSerializer.new(PostResource).serialize_to_hash(PostResource.new(post, nil))
This returns results like this:
{
"data": {
"type": "posts",
"id": "1",
"links": {
"self": "http://example.com/posts/1"
},
"attributes": {
"title": "New post",
"body": "A body!!!",
"subject": "New post"
},
"relationships": {
"section": {
"links": {
"self": "http://example.com/posts/1/relationships/section",
"related": "http://example.com/posts/1/section"
},
"data": null
},
"author": {
"links": {
"self": "http://example.com/posts/1/relationships/author",
"related": "http://example.com/posts/1/author"
},
"data": {
"type": "people",
"id": "1"
}
},
"tags": {
"links": {
"self": "http://example.com/posts/1/relationships/tags",
"related": "http://example.com/posts/1/tags"
}
},
"comments": {
"links": {
"self": "http://example.com/posts/1/relationships/comments",
"related": "http://example.com/posts/1/comments"
}
}
}
}
}
Serializer options
The ResourceSerializer
can be initialized with some optional parameters:
include
An array of resources. Nested resources can be specified with dot notation.
Purpose: determines which objects will be side loaded with the source objects in an included
section
Example: include: ['comments','author','comments.tags','author.posts']
fields
A hash of resource types and arrays of fields for each resource type.
Purpose: determines which fields are serialized for a resource type. This encompasses both attributes and relationship ids in the links section for a resource. Fields are global for a resource type.
Example: fields: { people: [:email, :comments], posts: [:title, :author], comments: [:body, :post]}
post = Post.find(1)
include_resources = ['comments','author','comments.tags','author.posts']
JSONAPI::ResourceSerializer.new(PostResource, include: include_resources,
fields: {
people: [:email, :comments],
posts: [:title, :author],
tags: [:name],
comments: [:body, :post]
}
).serialize_to_hash(PostResource.new(post, nil))
Routing
JR has a couple of helper methods available to assist you with setting up routes.
jsonapi_resources
Like resources
in ActionDispatch
, jsonapi_resources
provides resourceful routes mapping between HTTP verbs and URLs
and controller actions. This will also setup mappings for relationship URLs for a resource's relationships. For example:
Rails.application.routes.draw do
jsonapi_resources :contacts
jsonapi_resources :phone_numbers
end
gives the following routes
Prefix Verb URI Pattern Controller#Action
contact_relationships_phone_numbers GET /contacts/:contact_id/relationships/phone-numbers(.:format) contacts#show_relationship {:relationship=>"phone_numbers"}
POST /contacts/:contact_id/relationships/phone-numbers(.:format) contacts#create_relationship {:relationship=>"phone_numbers"}
DELETE /contacts/:contact_id/relationships/phone-numbers/:keys(.:format) contacts#destroy_relationship {:relationship=>"phone_numbers"}
contact_phone_numbers GET /contacts/:contact_id/phone-numbers(.:format) phone_numbers#get_related_resources {:relationship=>"phone_numbers", :source=>"contacts"}
contacts GET /contacts(.:format) contacts#index
POST /contacts(.:format) contacts#create
contact GET /contacts/:id(.:format) contacts#show
PATCH /contacts/:id(.:format) contacts#update
PUT /contacts/:id(.:format) contacts#update
DELETE /contacts/:id(.:format) contacts#destroy
phone_number_relationships_contact GET /phone-numbers/:phone_number_id/relationships/contact(.:format) phone_numbers#show_relationship {:relationship=>"contact"}
PUT|PATCH /phone-numbers/:phone_number_id/relationships/contact(.:format) phone_numbers#update_relationship {:relationship=>"contact"}
DELETE /phone-numbers/:phone_number_id/relationships/contact(.:format) phone_numbers#destroy_relationship {:relationship=>"contact"}
phone_number_contact GET /phone-numbers/:phone_number_id/contact(.:format) contacts#get_related_resource {:relationship=>"contact", :source=>"phone_numbers"}
phone_numbers GET /phone-numbers(.:format) phone_numbers#index
POST /phone-numbers(.:format) phone_numbers#create
phone_number GET /phone-numbers/:id(.:format) phone_numbers#show
PATCH /phone-numbers/:id(.:format) phone_numbers#update
PUT /phone-numbers/:id(.:format) phone_numbers#update
DELETE /phone-numbers/:id(.:format) phone_numbers#destroy
jsonapi_resource
Like jsonapi_resources
, but for resources you lookup without an id.
Nested Routes
By default nested routes are created for getting related resources and manipulating relationships. You can control the
nested routes by passing a block into jsonapi_resources
or jsonapi_resource
. An empty block will not create
any nested routes. For example:
Rails.application.routes.draw do
jsonapi_resources :contacts do
end
end
gives routes that are only related to the primary resource, and none for its relationships:
Prefix Verb URI Pattern Controller#Action
contacts GET /contacts(.:format) contacts#index
POST /contacts(.:format) contacts#create
contact GET /contacts/:id(.:format) contacts#show
PATCH /contacts/:id(.:format) contacts#update
PUT /contacts/:id(.:format) contacts#update
DELETE /contacts/:id(.:format) contacts#destroy
To manually add in the nested routes you can use the jsonapi_links
, jsonapi_related_resources
and
jsonapi_related_resource
inside the block. Or, you can add the default set of nested routes using the
jsonapi_relationships
method. For example:
Rails.application.routes.draw do
jsonapi_resources :contacts do
jsonapi_relationships
end
end
jsonapi_links
You can add relationship routes in with jsonapi_links
, for example:
Rails.application.routes.draw do
jsonapi_resources :contacts do
jsonapi_links :phone_numbers
end
end
Gives the following routes:
contact_relationships_phone_numbers GET /contacts/:contact_id/relationships/phone-numbers(.:format) contacts#show_relationship {:relationship=>"phone_numbers"}
POST /contacts/:contact_id/relationships/phone-numbers(.:format) contacts#create_relationship {:relationship=>"phone_numbers"}
DELETE /contacts/:contact_id/relationships/phone-numbers/:keys(.:format) contacts#destroy_relationship {:relationship=>"phone_numbers"}
contacts GET /contacts(.:format) contacts#index
POST /contacts(.:format) contacts#create
contact GET /contacts/:id(.:format) contacts#show
PATCH /contacts/:id(.:format) contacts#update
PUT /contacts/:id(.:format) contacts#update
DELETE /contacts/:id(.:format) contacts#destroy
The new routes allow you to show, create and destroy the relationships between resources.
jsonapi_related_resources
Creates a nested route to GET the related has_many resources. For example:
Rails.application.routes.draw do
jsonapi_resources :contacts do
jsonapi_related_resources :phone_numbers
end
end
gives the following routes:
Prefix Verb URI Pattern Controller#Action
contact_phone_numbers GET /contacts/:contact_id/phone-numbers(.:format) phone_numbers#get_related_resources {:relationship=>"phone_numbers", :source=>"contacts"}
contacts GET /contacts(.:format) contacts#index
POST /contacts(.:format) contacts#create
contact GET /contacts/:id(.:format) contacts#show
PATCH /contacts/:id(.:format) contacts#update
PUT /contacts/:id(.:format) contacts#update
DELETE /contacts/:id(.:format) contacts#destroy
A single additional route was created to allow you GET the phone numbers through the contact.
jsonapi_related_resource
Like jsonapi_related_resources
, but for has_one related resources.
Rails.application.routes.draw do
jsonapi_resources :phone_numbers do
jsonapi_related_resource :contact
end
end
gives the following routes:
Prefix Verb URI Pattern Controller#Action
phone_number_contact GET /phone-numbers/:phone_number_id/contact(.:format) contacts#get_related_resource {:relationship=>"contact", :source=>"phone_numbers"}
phone_numbers GET /phone-numbers(.:format) phone_numbers#index
POST /phone-numbers(.:format) phone_numbers#create
phone_number GET /phone-numbers/:id(.:format) phone_numbers#show
PATCH /phone-numbers/:id(.:format) phone_numbers#update
PUT /phone-numbers/:id(.:format) phone_numbers#update
DELETE /phone-numbers/:id(.:format) phone_numbers#destroy
Formatting
JR by default uses some simple rules to format (and unformat) an attribute for (de-)serialization. Strings and Integers are output to JSON
as is, and all other values have .to_s
applied to them. This outputs something in all cases, but it is certainly not
correct for every situation.
If you want to change the way an attribute is (de-)serialized you have a couple of ways. The simplest method is to create a getter (and setter) method on the resource which overrides the attribute and apply the (un-)formatting there. For example:
class PersonResource < JSONAPI::Resource
attributes :name, :email, :last_login_time
# Setter example
def email=(new_email)
@model.email = new_email.downcase
end
# Getter example
def last_login_time
@model.last_login_time.in_time_zone(@context[:current_user].time_zone).to_s
end
end
This is simple to implement for a one off situation, but not for example if you want to apply the same formatting rules to all DateTime fields in your system. Another issue is the attribute on the resource will always return a formatted response, whether you want it or not.
Value Formatters
To overcome the above limitations JR uses Value Formatters. Value Formatters allow you to control the way values are
handled for an attribute. The format
can be set per attribute as it is declared in the resource. For example:
class PersonResource < JSONAPI::Resource
attributes :name, :email, :spoken_languages
attribute :last_login_time, format: :date_with_utc_timezone
# Getter/Setter for spoken_languages ...
end
A Value formatter has a format
and an unformat
method. Here's the base ValueFormatter and DefaultValueFormatter for
reference:
module JSONAPI
class ValueFormatter < Formatter
class << self
def format(raw_value)
super(raw_value)
end
def unformat(value)
super(value)
end
...
end
end
end
class DefaultValueFormatter < JSONAPI::ValueFormatter
class << self
def format(raw_value)
case raw_value
when String, Integer
return raw_value
else
return raw_value.to_s
end
end
end
end
You can also create your own Value Formatter. Value Formatters must be named with the format
name followed by
ValueFormatter
, i.e. DateWithUTCTimezoneValueFormatter
and derive from JSONAPI::ValueFormatter
. It is
recommended that you create a directory for your formatters, called formatters
.
The format
method is called by the ResourceSerializer
as is serializing a resource. The format method takes the
raw_value
parameter. raw_value
is the value as read from the model.
The unformat
method is called when processing the request. Each incoming attribute (except links
) are run through
the unformat
method. The unformat
method takes a value
, which is the value as it comes in on the
request. This allows you process the incoming value to alter its state before it is stored in the model.
Use a Different Default Value Formatter
Another way to handle formatting is to set a different default value formatter. This will affect all attributes that do
not have a format
set. You can do this by overriding the default_attribute_options
method for a resource (or a base
resource for a system wide change).
def default_attribute_options
{format: :my_default}
end
and
class MyDefaultValueFormatter < JSONAPI::ValueFormatter
class << self
def format(raw_value)
case raw_value
when String, Integer
return raw_value
when DateTime
return raw_value.in_time_zone('UTC').to_s
else
return raw_value.to_s
end
end
end
end
This way all DateTime values will be formatted to display in the UTC timezone.
Key Format
By default JR uses dasherized keys as per the JSON API naming recommendations. This can be changed by specifying a different key formatter.
For example, to use camel cased keys with an initial lowercase character (JSON's default) create an initializer and add the following:
JSONAPI.configure do |config|
# built in key format options are :underscored_key, :camelized_key and :dasherized_key
config.json_key_format = :camelized_key
end
This will cause the serializer to use the CamelizedKeyFormatter
. You can also create your own KeyFormatter
, for
example:
class UpperCamelizedKeyFormatter < JSONAPI::KeyFormatter
class << self
def format(key)
super.camelize(:upper)
end
end
end
You would specify this in JSONAPI.configure
as :upper_camelized
.
Configuration
JR has a few configuration options. Some have already been mentioned above. To set configuration options create an initializer and add the options you wish to set. All options have defaults, so you only need to set the options that are different. The default options are shown below.
If using custom classes (such as the CountingActiveRecordOperationsProcessor, or a CustomPaginator), be sure to require them at the top of the initializer before usage.
JSONAPI.configure do |config|
#:underscored_key, :camelized_key, :dasherized_key, or custom
config.json_key_format = :dasherized_key
#:underscored_route, :camelized_route, :dasherized_route, or custom
config.route_format = :dasherized_route
#:basic, :active_record, or custom
config.operations_processor = :active_record
#:integer, :uuid, :string, or custom (provide a proc)
config.resource_key_type = :integer
# optional request features
config.allow_include = true
config.allow_sort = true
config.allow_filter = true
# How to handle unsupported attributes and relationships which are provided in the request
# true => raises an error
# false => allows the request to continue. A warning is included in the response meta data indicating
# the fields which were ignored. This is useful for client libraries which send extra parameters.
config.raise_if_parameters_not_allowed = true
# :none, :offset, :paged, or a custom paginator name
config.default_paginator = :none
# Output pagination links at top level
config.top_level_links_include_pagination = true
config.default_page_size = 10
config.maximum_page_size = 20
# Output the record count in top level meta data for find operations
config.top_level_meta_include_record_count = false
config.top_level_meta_record_count_key = :record_count
config.use_text_errors = false
# List of classes that should not be rescued by the operations processor.
# For example, if you use Pundit for authorization, you might
# raise a Pundit::NotAuthorizedError at some point during operations
# processing. If you want to use Rails' `rescue_from` macro to
# catch this error and render a 403 status code, you should add
# the `Pundit::NotAuthorizedError` to the `exception_class_whitelist`.
# Subclasses of the whitelisted classes will also be whitelisted.
config.exception_class_whitelist = []
# Resource Linkage
# Controls the serialization of resource linkage for non compound documents
# NOTE: always_include_to_many_linkage_data is not currently implemented
config.always_include_to_one_linkage_data = false
end
Contributing
- Fork it ( http://github.com/cerebris/jsonapi-resources/fork )
- Create your feature branch (
git checkout -b my-new-feature
) - Commit your changes (
git commit -am 'Add some feature'
) - Push to the branch (
git push origin my-new-feature
) - Create a new Pull Request
License
Copyright 2014 Cerebris Corporation. MIT License (see LICENSE for details).