# JSONAPI::Resources [](http://travis-ci.org/cerebris/jsonapi-resources)
JSONAPI::Resources, or "JR", provides a framework for developing a server that complies with the [JSON API](http://jsonapi.org/) 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, and provides custom routes, controllers, and serializers. JR's resources may be backed by ActiveRecord models or by custom objects.
## Demo App
We have a simple demo app, called [Peeps](https://github.com/cerebris/peeps), available to show how JR is used.
## 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:
```ruby
require 'jsonapi/resource'
class ContactResource < JSONAPI::Resource
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:
```ruby
require 'jsonapi/resource'
class ContactResource < JSONAPI::Resource
attribute :id
attribute :name_first
attributes :name_last, :email, :twitter
end
```
This resource has 5 attributes: `:id`, `:name_first`, `:name_last`, `:email`, `:twitter`. 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:
```ruby
require 'jsonapi/resource'
class ContactResource < JSONAPI::Resource
attributes :id, :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:
```ruby
class AuthorResource < JSONAPI::Resource
attributes :id, :name, :email
model_name 'Person'
has_many :posts
def fetchable_fields
if (context.current_user.guest)
super(context) - [:email]
else
super(context)
end
end
end
```
Context flows through from the controller and can be used to control the attributes based on the current user (or other value)).
##### Creatable and Updateable Attributes
By default all attributes are assumed to be updateable and creatable. To prevent some attributes from being accepted by the `update` or `create` methods, override the `self.updateable_fields` and `self.createable_fields` methods on a resource.
This example prevents `full_name` from being set:
```ruby
require 'jsonapi/resource'
class ContactResource < JSONAPI::Resource
attributes :id, :name_first, :name_last, :full_name
def full_name
"#{@model.name_first}, #{@model.name_last}"
end
def self.updateable_fields(context)
super - [:full_name]
end
def self.createable_fields(keys, 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 createable and updateable fields based on the user.
##### Sortable Attributes
JR supports [sorting primary resources by multiple sort criteria](http://jsonapi.org/format/#fetching-sorting).
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`:
```ruby
class PostResource < JSONAPI::Resource
attribute :id, :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 :id, :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](#value-formatters) section for more details.
#### Primary Key
Resources are always represented using a key of `id`. If the underlying model does not use `id` as the primary key you can use the `primary_key` method to tell the resource which field on the model to use as the primary key. Note: this doesn't have to be the actual primary key of the model. For example you may wish to use integers internally and a different scheme publicly.
```ruby
class CurrencyResource < JSONAPI::Resource
primary_key :code
attributes :code, :name
has_many :expense_entries
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:
```ruby
class AuthorResource < JSONAPI::Resource
attributes :id, :name
model_name 'Person'
has_many :posts
end
```
#### Associations
Related resources need to be specified in the resource. These are declared with the `has_one` and the `has_many` methods.
Here's a simple example where a post has a single author and an author can have many posts:
```ruby
class PostResource < JSONAPI::Resource
attribute :id, :title, :body
has_one :author
end
```
And the corresponding author:
```ruby
class AuthorResource < JSONAPI::Resource
attribute :id, :name
has_many :posts
end
```
##### Options
The association methods support the following options:
* `class_name` - a string specifying the underlying class for the related resource
* `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.
Examples:
```ruby
class CommentResource < JSONAPI::Resource
attributes :id, :body
has_one :post
has_one :author, class_name: 'Person'
has_many :tags, acts_as_set: true
end
```
```ruby
class ExpenseEntryResource < JSONAPI::Resource
attributes :id, :cost, :transaction_date
has_one :currency, class_name: 'Currency', key: 'currency_code'
has_one :employee
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:
```ruby
require 'jsonapi/resource'
class ContactResource < JSONAPI::Resource
attributes :id, :name_first, :name_last, :email, :twitter
filter :id
filters :name_first, :name_last
end
```
##### Finders
Basic finding by filters is supported by resources. However if you have more complex requirements for finding you can override the `find` and `find_by_key` methods on the resource.
Here's an example that defers the `find` operation to a `current_user` set on the `context` option:
```ruby
class AuthorResource < JSONAPI::Resource
attributes :id, :name
model_name 'Person'
has_many :posts
filter :name
def self.find(attrs, options = {})
context = options[:context]
authors = context.current_user.find_authors(attrs)
return authors.map do |author|
self.new(author)
end
end
end
```
### Controllers
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:
```ruby
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:
```ruby
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
```
#### Error codes
Error codes are provided for each error object returned, based on the error. These errors are:
```ruby
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_PARAM = 114
RECORD_NOT_FOUND = 404
LOCKED = 423
end
```
These codes can be customized in your app by creating an initializer to override any or all of the codes.
### Serializer
The `ResourceSerializer` can be used to serialize a resource into JSON API compliant JSON. `ResourceSerializer` has a `serialize_to_hash` method that takes a resource instance to serialize. For example:
```ruby
require 'jsonapi/resource_serializer'
post = Post.find(1)
JSONAPI::ResourceSerializer.new.serialize_to_hash(PostResource.new(post))
```
This returns results like this:
```ruby
{
posts: {
id: 1,
title: 'New post',
body: 'A body!!!',
links: {
section: nil,
author: 1,
tags: [1,2,3],
comments: [1,2]
}
}
}
```
#### Serialize_to_hash method options
The `serialize_to_hash` method also takes 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 a linked 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 association ids in the links section for a resource. Fields are global for a resource type.
*Example*: ```fields: { people: [:id, :email, :comments], posts: [:id, :title, :author], comments: [:id, :body, :post]}```
```ruby
post = Post.find(1)
JSONAPI::ResourceSerializer.new.serialize_to_hash(PostResource.new(post),
include: ['comments','author','comments.tags','author.posts'],
fields: {
people: [:id, :email, :comments],
posts: [:id, :title, :author],
tags: [:name],
comments: [:id, :body, :post]})
```
##### `context`
Context data can be provided to the serializer, which passes it to each resource as it is inspected.
#### 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 associations. For example
```ruby
require 'jsonapi/routing_ext'
Peeps::Application.routes.draw do
jsonapi_resources :contacts
jsonapi_resources :phone_numbers
end
```
gives the following routes
```
Prefix Verb URI Pattern Controller#Action
contact_links_phone_numbers GET /contacts/:contact_id/links/phone_numbers(.:format) contacts#show_association {:association=>"phone_numbers"}
POST /contacts/:contact_id/links/phone_numbers(.:format) contacts#create_association {:association=>"phone_numbers"}
DELETE /contacts/:contact_id/links/phone_numbers/:keys(.:format) contacts#destroy_association {:association=>"phone_numbers"}
contacts GET /contacts(.:format) contacts#index
POST /contacts(.:format) contacts#create
new_contact GET /contacts/new(.:format) contacts#new
edit_contact GET /contacts/:id/edit(.:format) contacts#edit
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_links_contact GET /phone_numbers/:phone_number_id/links/contact(.:format) phone_numbers#show_association {:association=>"contact"}
POST /phone_numbers/:phone_number_id/links/contact(.:format) phone_numbers#create_association {:association=>"contact"}
DELETE /phone_numbers/:phone_number_id/links/contact(.:format) phone_numbers#destroy_association {:association=>"contact"}
phone_numbers GET /phone_numbers(.:format) phone_numbers#index
POST /phone_numbers(.:format) phone_numbers#create
new_phone_number GET /phone_numbers/new(.:format) phone_numbers#new
edit_phone_number GET /phone_numbers/:id/edit(.:format) phone_numbers#edit
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.
##### `jsonapi_links`
You can control the relationship routes by passing a block into `jsonapi_resources` or `jsonapi_resource`. An empty block
will not create any relationship routes.
You can add relationship routes in with `jsonapi_links`, for example:
```ruby
Rails.application.routes.draw do
jsonapi_resources :posts, except: [:destroy] do
jsonapi_link :author, except: [:destroy]
jsonapi_links :tags, only: [:show, :create]
end
end
```
This will create relationship routes for author (show and create, but not destroy) and for tags (again show and create, but not destroy).
#### Formatting
JR by default uses some simple rules to format an attribute for 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 serialized you have a couple of ways. The simplest method is to create a getter method on the resource which overrides the attribute and apply the formatting there. For example:
```ruby
class PersonResource < JSONAPI::Resource
attributes :id, :name, :email
attribute :last_login_time
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:
```ruby
class PersonResource < JSONAPI::Resource
attributes :id, :name, :email
attribute :last_login_time, format: :date_with_timezone
end
```
A Value formatter has a `format` and an `unformat` method. Here's the base ValueFormatter and DefaultValueFormatter for reference:
```ruby
module JSONAPI
class ValueFormatter < Formatter
class << self
def format(raw_value, context)
super(raw_value)
end
def unformat(value, context)
super(value)
end
...
end
end
end
class DefaultValueFormatter < JSONAPI::ValueFormatter
class << self
def format(raw_value, context)
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. `DateWithTimezoneValueFormatter` 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`, and `context` parameters. `raw_value` is the value as read from the model, and `context` is the context of the current user/request. From this you can base the formatted version of the attribute current context.
The `unformat` method is called when processing the request. Each incoming attribute (except `links`) are run through the `unformat` method. The `unformat` method takes the `value`, and `context` parameters. `value` is the value as it comes in on the request, and `context` is the context of the current user/request. This allows you process the incoming value to alter its state before it is stored in the model. By default no processing is applied.
###### 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 notw 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).
```ruby
def default_attribute_options
{format: :my_default}
end
```
and
```ruby
class MyDefaultValueFormatter < JSONAPI::ValueFormatter
class << self
def format(raw_value, context)
case raw_value
when String, Integer
return raw_value
when DateTime
return raw_value.in_time_zone(context[:current_user].time_zone).to_s
else
return raw_value.to_s
end
end
end
end
```
This way all DateTime values will be formatted to display in the specified timezone.
#### Key Format
JSONAPI is agnostic on the format of the keys used in the responses. By default JR uses underscored keys which match the attribute names used by rails models. 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. Besides UnderscoredKeyFormatter and CamelizedKeyFormatter JR defines the DasherizedKeyFormatter. You can also create your own KeyFormatter, for example:
```ruby
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`.
## Contributing
1. Fork it ( http://github.com/cerebris/jsonapi-resources/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
## License
Copyright 2014 Cerebris Corporation. MIT License (see LICENSE for details).