Using Rails with the Amazon product advertising API

This tutorial will help you get started using the Amazon product advertising API in your Rails application. For each keyword or phrase, you can retrieve product listings from the Amazon marketplace and display them on your website. The listings in this tutorial include: the products title, URL, image and the price. You can add more product information such as product descriptions or reviews. To find out more, take a look at the Docs .

Get Started

Sign up for Amazon Web Services
Sign in to the AWS management Console and get your Amazon credentials AWS Access Key ID and AWS Secret Access Key

Create a new file in config/initializers, named amazon.rb and add this line

ENV[‘AMAZONRCDIR’] = “#{RAILS_ROOT}/config/”

Create a new file in config, named .amazonrc and add your Amazon credentials

associate = ‘your associate name’
email = ‘your email account’
password = ‘your password’
cache = true
key_id = ‘your key id’
secret_key_id = ‘your secret key id’
locale = ‘us’
encoding = ‘iso-8859-15’
style = ‘xml’

Create a migration file for your items object

script/generate scaffold Item name:string flag:boolean

Edit your migration, adding a default value of false to the flag column

class CreateItems < ActiveRecord::Migration
  def self.up
    create_table :items do |t|
      t.string :name
      t.boolean :flag,  :default => false
      t.timestamps
    end
  end
  def self.down
    drop_table :items
  end
end

Rake your migration

rake db:migrate

Install the ruby-aaws gem

gem install ruby-aaws

items_controller.rb

At the top of your controller add

require ‘amazon/aws’
require ‘amazon/aws/search’
include Amazon::AWS
include Amazon::AWS::Search

Amazon throws an error if no products are available for the item or if its given an odd string. To avoid the error we will add a filter that checks the item with Amazon after it is created or updated. If Amazon returns an error, the item.flag is set to true and we wont try to get products from Amazon based on that item.

after_filter :check_with_amazon, :only => [:create, :update]
def check_with_amazon   
   @[email protected]
    begin
      is = ItemSearch.new( 'All', { 'Keywords' => @check } )
      rg = ResponseGroup.new( 'Medium' )
      req = Request.new
      req.locale = 'us'
      resp = req.search( is, rg ) 
      items = resp.item_search_response.items.item   
    rescue  
      if Amazon::AWS::Error 
        @item.flag = 'true'
        @item.save
      end  
    end         
end

Reset your flag to false in the update method

@item.flag = false
@item.save

items_helper.rb

Set up a helper method ad_builder.rb. This will handle the heavy lifting, getting product results from Amazon and putting them into an array @amazon_list. Here is the entire module:

module ItemsHelper
  require 'amazon/aws'
  require 'amazon/aws/search'
  include Amazon::AWS
  include Amazon::AWS::Search
 def ad_builder(lookup_item)
    is = ItemSearch.new( 'All', { 'Keywords' => lookup_item } )
    rg = ResponseGroup.new( 'Medium' )
    req = Request.new
    req.locale = 'us'
    resp = req.search( is, rg ) 
    amaz_items = resp.item_search_response.items.item
    @amazon_list = []  
    @attrib_group = {}      
      amaz_items.each do |item|
        attribs = item.item_attributes
        unless attribs.list_price.nil? 
          unless item.small_image.nil?
          @attrib_group ={
            'title' => attribs.title,
            'price' => attribs.list_price.formatted_price,
            'url' => item.detail_page_url,
            'pic' => item.small_image.url  
           }
          @amazon_list  << @attrib_group
          end
        end
      end  
  end
end

The Views

show.html.erb

This checks the flag on your item name and passes it to the helper method ad_builder which returns an array (@amazon_list) containing your Amazon product results.

<%=h @item.name %> 
<% if @item.flag == false  %>
    <% ad_builder(@item.name)%>	
	<% @amazon_list.each do |t| %>
	    <div> 			 
		<img src="<%= t['pic']%>" > 		 		 
		<%= link_to t['title'], t['url'].to_s %>		 		 
		<%= t['price']%>  	
	    </div>  
	<%end%>	
<%end%>	

index.html.erb

 <% @items.each do |l| %>
  <%=h l.name %> 
    <% if l.flag == false  %>
 	 <% ad_builder(l.name)%>	
	 <% @amazon_list.each do |t| %>
		<div>
		   <img src="<%= t['pic']%>" > 
		   <%= link_to t['title'], t['url'].to_s %>
		   <%= t['price']%>
 		 </div>  
	 <%end%>	
    <%end%>	
<br>
<hr>
<% end %>

Caching

Amazon’s efficiency guidelines puts a limit of 2,000 requests per hour, so it’s a good idea to cache your amazon results. Amazon also requires that any cached item must be refreshed within 24 hours. Lucky for us, the ruby-aws gem checks the age of the cached item and refreshes it if it has expired. Railscasts has an excellent overview of caching in rails.

One method for setting rails cache is to edit your environmental file in config/environments/, setting the following lines to true.

config.cache_classes = true
config.action_controller.perform_caching = true

That’s it, fire up your server and test it out.

Relevant Links

• Amazon product advertising API
• Amazon Web Services(aws) Sign Up
• Amazon Product Advertising Docs
• ruby-aws Docs
• Railscasts – Caching in Rails