Warden Authention for JSON based API(s)

I am trying to authenticate using warden for JSON based APIs (web services). I have defined my password strategy inside config/initializers as password_strategy.rb which has an authenticate! method defined inside it. When I call this authenticate! method from my sessions controller's create method, parameters inside authenticate! are getting empty somehow, even though I can see my parameters inside the create method of the sessions controller. I'm not sure what magic is happening behind the scenes.

Since my parameters are empty, my authentication is detected as unauthorized and I am redirected to sessions new method for logging in again, even though my login credentials are correct.

Here is my code:

My POST request URL: localhost:3000/login.json Parameters:

{
  "emailID":"sangam.gupta@mobiloitte.com", 
  "encrypted_password":"XXXXXX"
}

# Sessions controller (sessions_controller.rb)
class SessionsController < ApplicationController
  skip_before_filter :authenticate!

  def new
    render :json => { :responseCode => "401",:responseMessage => "The email id or password you entered is incorrect. Please try again."}
  end

  def create
    authenticate!
    render :json => { :responseCode => "200",:responseMessage => "You have successfully logged in"}
  end
end

# Application Controller (application_controller.rb)
require 'globals_module.rb'

class ApplicationController < ActionController::Base
  include GlobalsModule

  prepend_before_filter :authenticate!

  helper_method :warden, :signed_in?, :current_user

  around_filter :wrap_in_transaction

  def wrap_in_transaction
    ActiveRecord::Base.transaction do
      yield
    end
  end

  def signed_in?
    !current_user.nil?
  end

  def current_user
    warden.user
  end

  def warden
    request.env['warden']
  end

  def authenticate!
    Rails.logger.info params[:emailID] # email ID is present
    Rails.logger.info params[:encrypted_password] #encrypted password is present
    warden.authenticate!
  end
end

# Password Strategy (password_strategy.rb in config/initializer)
class PasswordStrategy < Warden::Strategies::Base
  def authenticate!
    Rails.logger.info params # params are empty, although present before calling authenticate! method
    Rails.logger.info request.session["emailID"] # It's are empty either
    user = User.find_by_emailID(params[:emailID])
    # my authentication code goes here
  end 
end

Warden::Strategies.add(:password, PasswordStrategy)

Any help would be appreciated. Thanks in advance.