Rails: Restrict API requests to JSON format

Question

I would like to restrict requests to all API controllers to being redirected to the JSON path. I would like to use a redirect since also the URL should change according to the response.
One option would be to use a before_filter which redirects the request to the same action but forces the JSON format. The example is not working yet!

# base_controller.rb
class Api::V1::BaseController < InheritedResources::Base
  before_filter :force_response_format
  respond_to :json
  def force_response_format
    redirect_to, params[:format] = :json
  end
end

Another option would be to restrict the format in the routes settings.

# routes.rb
MyApp::Application.routes.draw do
  namespace :api, defaults: { format: 'json' } do
    namespace :v1 do
      resources :posts
    end
  end
end

I want all request to end up as a JSON request:

http://localhost:3000/api/v1/posts
http://localhost:3000/api/v1/posts.html
http://localhost:3000/api/v1/posts.xml
http://localhost:3000/api/v1/posts.json
...

Which strategy would you recommend?

Leo Correa · Accepted Answer · 2013-02-02 17:14:23Z

23

Setting a default in your routes won't turn all requests into a JSON request.

What you want is to make sure that whatever you're rendering is a JSON response

You pretty much had it in the first option except you need to do this

before_filter :set_default_response_format

private
  def set_default_response_format
    request.format = :json
  end

That would go under your Base API controller so that when it gets to your actual action the format will always be JSON.

answered Feb 2, 2013 at 17:14

Leo Correa

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4 Comments

JJD Over a year ago

Setting the request.format to :json solves the problem that all responses return JSON. It does however not change the URL in the addressbar.

Leo Correa Over a year ago

If you're doing an API why would you need to write the URL in the address bar? Note that doing a redirect would return a 300 status and its probably not the most efficient, don't quote me on that though.

JJD Over a year ago

This being said, would you then recommend to rewrite the request format to JSON in any case? Another option would be to return some HTTP status as mathieugagne and you mentioned.

Leo Correa Over a year ago

These are design options that you have to consider for your API. Do you want to just accept/return JSON or are you open for returning XML and other formats...

JJD · Accepted Answer · 2013-02-02 23:49:43Z

17

If you want to return a 404, or raise a RouteNotFound error if the format is not :json, I would add a route constraint like this:

Require JSON format:

# routes.rb
MyApp::Application.routes.draw do
  namespace :api, constraints: { format: 'json' } do
    namespace :v1 do
      resources :posts
    end
  end
end

More information can be found here: http://edgeguides.rubyonrails.org/routing.html#request-based-constraints

edited Feb 2, 2013 at 23:49

JJD

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answered Feb 2, 2013 at 20:39

PeppyHeppy

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2 Comments

asymmetric Over a year ago

I would argue that a 406 is a more accurate response in this case. Any Idea why this approach returns a 404?

dgmstuart Over a year ago

@asymmetric It's because the constraint says "this rule only matches json requests", so any non-json requests won't match and will fall through to the end unless you have a specific later rule which matches non-json requests and responds explicitly with another response.

Eric Platon · Accepted Answer · 2014-09-23 04:45:48Z

5

Second option, using routes format. If a user explicitly requests a XML format, he should not receive a JSON response. He should get a message saying that this URL doesn't answer to XML format, or 404.

By the way, it would be rather easy to respond to all which is what you should do in my opinion.

class FooController
  respond_to :xml, :json
  def show
    @bar = Bar.find(params[:id])
    respond_with(@bar)
  end
end

edited Sep 23, 2014 at 4:45

Eric Platon

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answered Feb 2, 2013 at 17:08

mathieugagne

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1 Comment

Eric Platon Over a year ago

+1 for the beginning of the comment. Adding a format is not that easy in my experience, although Rails make it easy to implement. The API designer still has to think through what it means to support an additional format, with all the implications.

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