Lost sleep over JSON and Rack::PostBodyContentTypeParser

I’ve been fighting this issue the last couple nights. I wrote earlier about how Rack::PostBodyContentTypeParser can automagically turn a posted JSON object into a Rack / Sinatra params hash. So, I wrote some tests to make sure this was the case and moved on. Well, it turns out in real life things weren’t working and I couldn’t figure out why. Everything looked cool, but the hash wasn’t getting set when I did an AJAX call in the browser – everything was empty. I looked at everything, from the server, to the JS library, to the browser, to setting different content types in prototype.js etc… UGH!

The short of it is that Rack::PostBodyContentTypeParser requires exactly application/json in order to automagically turn the posted JSON object into Rack params and prototype.js (and jquery.js were adding an encoding type of charset=UTF-8 so the entire header entry was coming across as this CONTENT_TYPE: application/json; charset=UTF-8. So, as a fix, I’m just including the Rack::PostBodyContentTypeParser in the Sinatra application with one small change. Here’s the code:

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module Rack
 
  # A Rack middleware for parsing POST/PUT body data when Content-Type is
  # not one of the standard supported types, like <tt>application/json</tt>.
  #
  # TODO: Find a better name.
  #
  class PostBodyContentTypeParser
 
    # Constants
    #
    CONTENT_TYPE = 'CONTENT_TYPE'.freeze
    POST_BODY = 'rack.input'.freeze
    FORM_INPUT = 'rack.request.form_input'.freeze
    FORM_HASH = 'rack.request.form_hash'.freeze
 
    # Supported Content-Types
    #
 
    ################## turned into regex so it matches type with encoding data...
    #APPLICATION_JSON = 'application/json'.freeze
    APPLICATION_JSON = /^application\/json/.freeze
 
    def initialize(app)
      @app = app
    end
 
    def call(env)
      case env[CONTENT_TYPE]
      when APPLICATION_JSON
        env.update(FORM_HASH => JSON.parse(env[POST_BODY].read), FORM_INPUT => env[POST_BODY])
      end
      @app.call(env)
    end
 
  end
end

I tested that this worked by writing the following:

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def test_post_as_json_converts_to_params
  # sanity check that post with normal params works...
  post '/test_params_as_json', :param1=>"param one"
  assert_equal last_response.body,"params[:param1]=param one"
  post '/test_params_as_json', {:param1=>"param one"}.to_json, "CONTENT_TYPE"=>"application/json"
  assert_equal last_response.body,"params[:param1]=param one"
  # this is the problem, adding a charset to the content type seems to breaks rack-contrib/post_body_content_type_parser.rb
  post '/test_params_as_json', {:param1=>"param one"}.to_json, "CONTENT_TYPE"=>"application/json; charset=UTF-8"
  assert_equal last_response.body,"params[:param1]=param one"    
end
Posted: April 4th, 2010 | Author: | Filed under: Code | Tags: , , , , , , , , | 4 Comments »

Using Rack middleware to parse JSON

In attempting to AJAX-ize the site, I had the desire to handle JSON as if it were form post data. Queue a Rack middleware solution. rack-contrib contains a bunch of common middleware extensions, one being the horribly named PostBodyContentTypeParser. To get this working I added:

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require 'rack/contrib'

with all of the rest of the required files.

Added:

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use Rack::PostBodyContentTypeParser

to my application class

And went about over testing it like so:

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def test_json_creates_params_hash
  params_hash={"user"=>{"username"=>"testuser","email"=>"test@test.com","password"=>"pass1","password_confirmation"=>"pass1"}}
  post '/test_json', params_hash
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
  json_string="{\"user\":{\"password_confirmation\":\"pass1\",\"username\":\"testuser\",\"password\":\"pass1\",\"email\":\"test@test.com\"}}"
  post '/test_json', JSON(json_string)
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
  post '/test_json', json_string, "CONTENT_TYPE"=>"application/json"
  assert_equal last_request.env["CONTENT_TYPE"], "application/json"
  assert !last_request.params.blank?
  assert_equal params_hash, last_request.params
  assert last_response.ok?
end
Posted: March 30th, 2010 | Author: | Filed under: Code | Tags: , , , , , , , | 1 Comment »