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Hanami::Controller

Complete, fast and testable actions for Rack and Hanami

Version

This branch contains the code for hanami-controller 2.x.

Status

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Contact

Rubies

Hanami::Controller supports Ruby (MRI) 2.6+

Installation

Add this line to your application's Gemfile:

gem "hanami/controller"

And then execute:

$ bundle

Or install it yourself as:

$ gem install hanami-controller

Usage

Hanami::Controller is a micro library for web frameworks. It works beautifully with Hanami::Router, but it can be employed everywhere. It's designed to be fast and testable.

Actions

The core of this framework are the actions. They are the endpoints that respond to incoming HTTP requests.

class Show < Hanami::Action
  def handle(req, res)
    res[:article] = ArticleRepository.new.find(req.params[:id])
  end
end

Hanami::Action follows the Hanami philosophy: a single purpose object with a minimal interface.

In this case, Hanami::Action provides the key public interface of #call(env), making your actions Rack-compatible. To provide custom behaviour when your actions are being called, you can implement #handle(req, res)

An action is an object and you have full control over it. In other words, you have the freedom to instantiate, inject dependencies and test it, both at the unit and integration level.

In the example below, the default repository is ArticleRepository. During a unit test we can inject a stubbed version, and invoke #call with the params. We're avoiding HTTP calls, we're also going to avoid hitting the database (it depends on the stubbed repository), we're just dealing with message passing. Imagine how fast the unit test could be.

class Show < Hanami::Action
  def initialize(configuration:, repository: ArticleRepository.new)
    @repository = repository
    super(configuration: configuration)
  end

  def handle(req, res)
    res[:article] = repository.find(req.params[:id])
  end

  private

  attr_reader :repository
end

configuration = Hanami::Controller::Configuration.new
action = Show.new(configuration: configuration, repository: ArticleRepository.new)
action.call(id: 23)

Params

The request params are part of the request passed as an argument to the #handle method. If routed with Hanami::Router, it extracts the relevant bits from the Rack env (eg the requested :id). Otherwise everything is passed as is: the full Rack env in production, and the given Hash for unit tests.

With Hanami::Router:

class Show < Hanami::Action
  def handle(req, *)
    # ...
    puts req.params # => { id: 23 } extracted from Rack env
  end
end

Standalone:

class Show < Hanami::Action
  def handle(req, *)
    # ...
    puts req.params # => { :"rack.version"=>[1, 2], :"rack.input"=>#<StringIO:0x007fa563463948>, ... }
  end
end

Unit Testing:

class Show < Hanami::Action
  def handle(req, *)
    # ...
    puts req.params # => { id: 23, key: "value" } passed as it is from testing
  end
end

action   = Show.new(configuration: configuration)
response = action.call(id: 23, key: "value")

Whitelisting

Params represent an untrusted input. For security reasons it's recommended to whitelist them.

require "hanami/validations"
require "hanami/controller"

class Signup < Hanami::Action
  params do
    required(:first_name).filled(:str?)
    required(:last_name).filled(:str?)
    required(:email).filled(:str?)

    required(:address).schema do
      required(:line_one).filled(:str?)
      required(:state).filled(:str?)
      required(:country).filled(:str?)
    end
  end

  def handle(req, *)
    # Describe inheritance hierarchy
    puts req.params.class            # => Signup::Params
    puts req.params.class.superclass # => Hanami::Action::Params

    # Whitelist :first_name, but not :admin
    puts req.params[:first_name]     # => "Luca"
    puts req.params[:admin]          # => nil

    # Whitelist nested params [:address][:line_one], not [:address][:line_two]
    puts req.params[:address][:line_one] # => "69 Tender St"
    puts req.params[:address][:line_two] # => nil
  end
end

Validations & Coercions

Because params are a well defined set of data required to fulfill a feature in your application, you can validate them. So you can avoid hitting lower MVC layers when params are invalid.

If you specify the :type option, the param will be coerced.

require "hanami/validations"
require "hanami/controller"

class Signup < Hanami::Action
  MEGABYTE = 1024 ** 2

  params do
    required(:first_name).filled(:str?)
    required(:last_name).filled(:str?)
    required(:email).filled?(:str?, format?: /\[email protected]+\z/)
    required(:password).filled(:str?).confirmation
    required(:terms_of_service).filled(:bool?)
    required(:age).filled(:int?, included_in?: 18..99)
    optional(:avatar).filled(size?: 1..(MEGABYTE * 3))
  end

  def handle(req, *)
    halt 400 unless req.params.valid?
    # ...
  end
end

Response

The output of #call is a Hanami::Action::Response:

class Show < Hanami::Action
end

action = Show.new(configuration: configuration)
action.call({}) # => #<Hanami::Action::Response:0x00007fe8be968418 @status=200 ...>

This is the same res response object passed to #handle, where you can use its accessors to explicitly set status, headers, and body:

class Show < Hanami::Action
  def handle(*, res)
    res.status  = 201
    res.body    = "Hi!"
    res.headers.merge!("X-Custom" => "OK")
  end
end

action = Show.new
action.call({}) # => [201, { "X-Custom" => "OK" }, ["Hi!"]]

Exposures

In case you need to send data from the action to other layers of your application, you can use exposures. By default, an action exposes the received params.

class Show < Hanami::Action
  def handle(req, res)
    res[:article] = ArticleRepository.new.find(req.params[:id])
  end
end

action   = Show.new(configuration: configuration)
response = action.call(id: 23)

article = response[:article]
article.class # => Article
article.id # => 23

response.exposures.keys # => [:params, :article]

Callbacks

If you need to execute logic before or after #handle is invoked, you can use callbacks. They are useful for shared logic like authentication checks.

class Show < Hanami::Action
  before :authenticate, :set_article

  def handle(*)
  end

  private

  def authenticate
    # ...
  end

  # `req` and `res` in the method signature is optional
  def set_article(req, res)
    res[:article] = ArticleRepository.new.find(req.params[:id])
  end
end

Callbacks can also be expressed as anonymous lambdas:

class Show < Hanami::Action
  before { ... } # do some authentication stuff
  before { |req, res| res[:article] = ArticleRepository.new.find(req.params[:id]) }

  def handle(*)
  end
end

Exceptions management

When the app raises an exception, hanami-controller, does NOT manage it. You can write custom exception handling on per action or configuration basis.

An exception handler can be a valid HTTP status code (eg. 500, 401), or a Symbol that represents an action method.

class Show < Hanami::Action
  handle_exception StandardError => 500

  def handle(*)
    raise
  end
end

action = Show.new(configuration: configuration)
action.call({}) # => [500, {}, ["Internal Server Error"]]

You can map a specific raised exception to a different HTTP status.

class Show < Hanami::Action
  handle_exception RecordNotFound => 404

  def handle(*)
    raise RecordNotFound
  end
end

action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["Not Found"]]

You can also define custom handlers for exceptions.

class Create < Hanami::Action
  handle_exception ArgumentError => :my_custom_handler

  gle(*)
    raise ArgumentError.new("Invalid arguments")
  end

  private

  def my_custom_handler(req, res, exception)
    res.status = 400
    res.body   = exception.message
  end
end

action = Create.new(configuration: configuration)
action.call({}) # => [400, {}, ["Invalid arguments"]]

Exception policies can be defined globally via configuration:

configuration = Hanami::Controller::Configuration.new do |config|
  config.handle_exception RecordNotFound => 404
end

class Show < Hanami::Action
  def handle(*)
    raise RecordNotFound
  end
end

action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["Not Found"]]

Inherited Exceptions

class MyCustomException < StandardError
end

module Articles
  class Index < Hanami::Action
    handle_exception MyCustomException => :handle_my_exception

    def handle(*)
      raise MyCustomException
    end

    private

    def handle_my_exception(req, res, exception)
      # ...
    end
  end

  class Show < Hanami::Action
    handle_exception StandardError => :handle_standard_error

    def handle(*)
      raise MyCustomException
    end

    private

    def handle_standard_error(req, res, exception)
      # ...
    end
  end
end

Articles::Index.new.call({}) # => `handle_my_exception` will be invoked
Articles::Show.new.call({})  # => `handle_standard_error` will be invoked,
                             #   because `MyCustomException` inherits from `StandardError`

Throwable HTTP statuses

When #halt is used with a valid HTTP code, it stops the execution and sets the proper status and body for the response:

class Show < Hanami::Action
  before :authenticate!

  def handle(*)
    # ...
  end

  private

  def authenticate!
    halt 401 unless authenticated?
  end
end

action = Show.new(configuration: configuration)
action.call({}) # => [401, {}, ["Unauthorized"]]

Alternatively, you can specify a custom message.

class Show < Hanami::Action
  def handle(req, res)
    res[:droid] = DroidRepository.new.find(req.params[:id]) or not_found
  end

  private

  def not_found
    halt 404, "This is not the droid you're looking for"
  end
end

action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["This is not the droid you're looking for"]]

Cookies

You can read the original cookies sent from the HTTP client via req.cookies. If you want to send cookies in the response, use res.cookies.

They are read as a Hash from Rack env:

require "hanami/controller"
require "hanami/action/cookies"

class ReadCookiesFromRackEnv < Hanami::Action
  include Hanami::Action::Cookies

  def handle(req, *)
    # ...
    req.cookies[:foo] # => "bar"
  end
end

action = ReadCookiesFromRackEnv.new(configuration: configuration)
action.call({"HTTP_COOKIE" => "foo=bar"})

They are set like a Hash:

require "hanami/controller"
require "hanami/action/cookies"

class SetCookies < Hanami::Action
  include Hanami::Action::Cookies

  def handle(*, res)
    # ...
    res.cookies[:foo] = "bar"
  end
end

action = SetCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=bar"}, "..."]

They are removed by setting their value to nil:

require "hanami/controller"
require "hanami/action/cookies"

class RemoveCookies < Hanami::Action
  include Hanami::Action::Cookies

  def handle(*, res)
    # ...
    res.cookies[:foo] = nil
  end
end

action = RemoveCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=; max-age=0; expires=Thu, 01 Jan 1970 00:00:00 -0000"}, "..."]

Default values can be set in configuration, but overridden case by case.

require "hanami/controller"
require "hanami/action/cookies"

configuration = Hanami::Controller::Configuration.new do |config|
  config.cookies(max_age: 300) # 5 minutes
end

class SetCookies < Hanami::Action
  include Hanami::Action::Cookies

  def handle(*, res)
    # ...
    res.cookies[:foo] = { value: "bar", max_age: 100 }
  end
end

action = SetCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=bar; max-age=100;"}, "..."]

Sessions

Actions have builtin support for Rack sessions. Similarly to cookies, you can read the session sent by the HTTP client via req.session, and also manipulate it via res.ression.

require "hanami/controller"
require "hanami/action/session"

class ReadSessionFromRackEnv < Hanami::Action
  include Hanami::Action::Session

  def handle(req, *)
    # ...
    req.session[:age] # => "35"
  end
end

action = ReadSessionFromRackEnv.new(configuration: configuration)
action.call({ "rack.session" => { "age" => "35" } })

Values can be set like a Hash:

require "hanami/controller"
require "hanami/action/session"

class SetSession < Hanami::Action
  include Hanami::Action::Session

  def handle(*, res)
    # ...
    res.session[:age] = 31
  end
end

action = SetSession.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie"=>"rack.session=..."}, "..."]

Values can be removed like a Hash:

require "hanami/controller"
require "hanami/action/session"

class RemoveSession < Hanami::Action
  include Hanami::Action::Session

  def handle(*, res)
    # ...
    res.session[:age] = nil
  end
end

action = RemoveSession.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie"=>"rack.session=..."}, "..."] it removes that value from the session

While Hanami::Controller supports sessions natively, it's session store agnostic. You have to specify the session store in your Rack middleware configuration (eg config.ru).

use Rack::Session::Cookie, secret: SecureRandom.hex(64)
run Show.new(configuration: configuration)

HTTP Cache

Hanami::Controller sets your headers correctly according to RFC 2616 / 14.9 for more on standard cache control directives: http://tools.ietf.org/html/rfc2616#section-14.9.1

You can easily set the Cache-Control header for your actions:

require "hanami/controller"
require "hanami/action/cache"

class HttpCacheController < Hanami::Action
  include Hanami::Action::Cache
  cache_control :public, max_age: 600 # => Cache-Control: public, max-age=600

  def handle(*)
    # ...
  end
end

Expires header can be specified using expires method:

require "hanami/controller"
require "hanami/action/cache"

class HttpCacheController < Hanami::Action
  include Hanami::Action::Cache
  expires 60, :public, max_age: 600 # => Expires: Sun, 03 Aug 2014 17:47:02 GMT, Cache-Control: public, max-age=600

  def handle(*)
    # ...
  end
end

Conditional Get

According to HTTP specification, conditional GETs provide a way for web servers to inform clients that the response to a GET request hasn't change since the last request returning a 304 (Not Modified) response.

Passing the HTTP_IF_NONE_MATCH (content identifier) or HTTP_IF_MODIFIED_SINCE (timestamp) headers allows the web server define if the client has a fresh version of a given resource.

You can easily take advantage of Conditional Get using #fresh method:

require "hanami/controller"
require "hanami/action/cache"

class ConditionalGetController < Hanami::Action
  include Hanami::Action::Cache

  def handle(*)
    # ...
    fresh etag: resource.cache_key
    # => halt 304 with header IfNoneMatch = resource.cache_key
  end
end

If resource.cache_key is equal to IfNoneMatch header, then hanami will halt 304.

An alterative to hashing based check, is the time based check:

require "hanami/controller"
require "hanami/action/cache"

class ConditionalGetController < Hanami::Action
  include Hanami::Action::Cache

  def handle(*)
    # ...
    fresh last_modified: resource.update_at
    # => halt 304 with header IfModifiedSince = resource.update_at.httpdate
  end
end

If resource.update_at is equal to IfModifiedSince header, then hanami will halt 304.

Redirect

If you need to redirect the client to another resource, use res.redirect_to:

class Create < Hanami::Action
  def handle(*, res)
    # ...
    res.redirect_to "http://example.com/articles/23"
  end
end

action = Create.new(configuration: configuration)
action.call({ article: { title: "Hello" }}) # => [302, {"Location" => "/articles/23"}, ""]

You can also redirect with a custom status code:

class Create < Hanami::Action
  def handle(*, res)
    # ...
    res.redirect_to "http://example.com/articles/23", status: 301
  end
end

action = Create.new(configuration: configuration)
action.call({ article: { title: "Hello" }}) # => [301, {"Location" => "/articles/23"}, ""]

MIME Types

Hanami::Action automatically sets the Content-Type header, according to the request.

class Show < Hanami::Action
  def handle(*)
  end
end

action = Show.new(configuration: configuration)

response = action.call({ "HTTP_ACCEPT" => "*/*" }) # Content-Type "application/octet-stream"
response.format                                    # :all

response = action.call({ "HTTP_ACCEPT" => "text/html" }) # Content-Type "text/html"
response.format                                          # :html

However, you can force this value:

class Show < Hanami::Action
  def handle(*, res)
    # ...
    res.format = format(:json)
  end
end

action = Show.new(configuration: configuration)

response = action.call({ "HTTP_ACCEPT" => "*/*" }) # Content-Type "application/json"
response.format                                    # :json

response = action.call({ "HTTP_ACCEPT" => "text/html" }) # Content-Type "application/json"
response.format                                          # :json

You can restrict the accepted MIME types:

class Show < Hanami::Action
  accept :html, :json

  def handle(*)
    # ...
  end
end

# When called with "\*/\*"            => 200
# When called with "text/html"        => 200
# When called with "application/json" => 200
# When called with "application/xml"  => 406

You can check if the requested MIME type is accepted by the client.

class Show < Hanami::Action
  def handle(req, res)
    # ...
    # @_env["HTTP_ACCEPT"] # => "text/html,application/xhtml+xml,application/xml;q=0.9"

    req.accept?("text/html")        # => true
    req.accept?("application/xml")  # => true
    req.accept?("application/json") # => false
    res.format                      # :html



    # @_env["HTTP_ACCEPT"] # => "*/*"

    req.accept?("text/html")        # => true
    req.accept?("application/xml")  # => true
    req.accept?("application/json") # => true
    res.format                      # :html
  end
end

Hanami::Controller is shipped with an extensive list of the most common MIME types. Also, you can register your own:

configuration = Hanami::Controller::Configuration.new do |config|
  config.format custom: "application/custom"
end

class Index < Hanami::Action
  def handle(*)
  end
end

action = Index.new(configuration: configuration)

response = action.call({ "HTTP_ACCEPT" => "application/custom" }) # => Content-Type "application/custom"
response.format                                                   # => :custom

class Show < Hanami::Action
  def handle(*, res)
    # ...
    res.format = format(:custom)
  end
end

action = Show.new(configuration: configuration)

response = action.call({ "HTTP_ACCEPT" => "*/*" }) # => Content-Type "application/custom"
response.format                                    # => :custom

Streamed Responses

When the work to be done by the server takes time, it may be a good idea to stream your response. Here's an example of a streamed CSV.

configuration = Hanami::Controller::Configuration.new do |config|
  config.format csv: 'text/csv'
end

class Csv < Hanami::Action
  def handle(*, res)
    res.format = format(:csv)
    res.body = Enumerator.new do |yielder|
      yielder << csv_header

      # Expensive operation is streamed as each line becomes available
      csv_body.each_line do |line|
        yielder << line
      end
    end
  end
end

Note:

  • In development, Hanami' code reloading needs to be disabled for streaming to work. This is because Shotgun interferes with the streaming action. You can disable it like this hanami server --code-reloading=false
  • Streaming does not work with WEBrick as it buffers its response. We recommend using puma, though you may find success with other servers

No rendering, please

Hanami::Controller is designed to be a pure HTTP endpoint, rendering belongs to other layers of MVC. You can set the body directly (see response), or use Hanami::View.

Controllers

A Controller is nothing more than a logical group of actions: just a Ruby module.

module Articles
  class Index < Hanami::Action
    # ...
  end

  class Show < Hanami::Action
    # ...
  end
end

Articles::Index.new(configuration: configuration).call({})

Hanami::Router integration

require "hanami/router"
require "hanami/controller"

module Web
  module Controllers
    module Books
      class Show < Hanami::Action
        def handle(*)
        end
      end
    end
  end
end

configuration = Hanami::Controller::Configuration.new
router = Hanami::Router.new(configuration: configuration, namespace: Web::Controllers) do
  get "/books/:id", "books#show"
end

Rack integration

Hanami::Controller is compatible with Rack. If you need to use any Rack middleware, please mount them in config.ru.

Configuration

Hanami::Controller can be configured via Hanami::Controller::Configuration. It supports a few options:

require "hanami/controller"

configuration = Hanami::Controller::Configuration.new do |config|
  # If the given exception is raised, return that HTTP status
  # It can be used multiple times
  # Argument: hash, empty by default
  #
  config.handle_exception ArgumentError => 404

  # Register a format to MIME type mapping
  # Argument: hash, key: format symbol, value: MIME type string, empty by default
  #
  config.format custom: "application/custom"

  # Define a fallback format to detect in case of HTTP request with `Accept: */*`
  # If not defined here, it will return Rack's default: `application/octet-stream`
  # Argument: symbol, it should be already known. defaults to `nil`
  #
  config.default_request_format = :html

  # Define a default format to set as `Content-Type` header for response,
  # unless otherwise specified.
  # If not defined here, it will return Rack's default: `application/octet-stream`
  # Argument: symbol, it should be already known. defaults to `nil`
  #
  config.default_response_format = :html

  # Define a default charset to return in the `Content-Type` response header
  # If not defined here, it returns `utf-8`
  # Argument: string, defaults to `nil`
  #
  config.default_charset = "koi8-r"
end

Thread safety

An Action is immutable, it works without global state, so it's thread-safe by design.

Versioning

Hanami::Controller uses Semantic Versioning 2.0.0

Contributing

  1. Fork it
  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 new Pull Request

Copyright

Copyright © 2014-2021 Luca Guidi – Released under MIT License

This project was formerly known as Lotus (lotus-controller).


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