rescue_from ActionController::RoutingError in Rails 4

In application_controller.rb add the following:

  # You want to get exceptions in development, but not in production.  unless Rails.application.config.consider_all_requests_local    rescue_from ActionController::RoutingError, with: -> { render_404  }  end  def render_404    respond_to do |format|      format.html { render template: 'errors/not_found', status: 404 }      format.all { render nothing: true, status: 404 }    end  end

I usually also rescue following exceptions, but that's up to you:

rescue_from ActionController::UnknownController, with: -> { render_404  }rescue_from ActiveRecord::RecordNotFound,        with: -> { render_404  }

Create the errors controller:

class ErrorsController < ApplicationController  def error_404    render 'errors/not_found'  endend

Then in routes.rb

  unless Rails.application.config.consider_all_requests_local    # having created corresponding controller and action    get '*path', to: 'errors#error_404', via: :all  end

And the last thing is to create not_found.html.haml (or whatever template engine you use) under /views/errors/:

  %span 404  %br  Page Not Found

@Andrey Deineko, your solution seems to work only for the RoutingErrors raised manually inside a conrtoller. If I try it with the url my_app/not_existing_path, I still get the standard error message.

I guess this is because the application doesn't even reach the controllers, since Rails raises the error before.

The trick that solved the problem for me was to add the following line at the end of the routes:

Rails.application.routes.draw do  # existing paths  match '*path' => 'errors#error_404', via: :allend

to catch all not predefined requests.

Then in the ErrorsController you can use respond_to to serve html, json... requests:

class ErrorsController < ApplicationController  def error_404    @requested_path = request.path    repond_to do |format|      format.html      format.json { render json: {routing_error: @requested_path} }    end  endend

Copying favicon image in app/assets/images worked for me.