Rails: Restrict API requests to JSON format

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_formatprivate  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.

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.rbMyApp::Application.routes.draw do  namespace :api, constraints: { format: 'json' } do    namespace :v1 do      resources :posts    end  endend

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

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)  endend