scratch.rb

# If you post to a Ruby on Rails REST API endpoint, then you'll get an
# InvalidAuthenticityToken exception unless you set a different
# content type in the request headers, since any post from a form must
# contain an authenticity token.
#
# This example shows you how to post to a rails endpoint.

require 'json'

def post_to_endpoint(endpoint)
  uri = URI.parse(endpoint)

  post_params = { 
    :title => "2BR Apartment For Rent in NYC",
    :description => "Great midtown west location. I love this place.",
    :price => "1500",
    :api_key => "my_api_key"
  }

  # Convert the parameters into JSON and set the content type as application/json
  req = Net::HTTP::Post.new(uri.path)
  req.body = JSON.generate(post_params)
  req["Content-Type"] = "application/json"
  
  http = Net::HTTP.new(uri.host, uri.port)
  response = http.start {|htt| htt.request(req)}
end

haaaaa, i use it to login redmine, to get login session cookie,

you can also manually put the authentication tokens in the form submission request headers.