High-Performance XML Parsing

20080729.xml

<?xml version='1.0'?>
<!--
 ! Excerpted from "Enterprise Recipes for Ruby and Rails"
 ! xml file containing credit card transaction.
 ! 应用的目录为： ccdemo/data/cc_xactions/20080729.xml
 -->
<cc-xactions date='20080729'>
  <cc-xaction id='100001' cc-ref='2537403' type='credit' amount='12.00'>
    <text>Monthly bill.</text>
  </cc-xaction>
  <!-- ... -->
  <cc-xaction id='400224' cc-ref='95932' type='purchase' amount='19.99'>
    <text>A new book.</text>
  </cc-xaction>
</cc-xactions>

credit_card_transaction.rb

<!--
 ! The Model for credit card transaction
 ! 应用的目录为：/ccdemo/app/models/credit_card_transaction.rb
 -->

require 'xml/libxml'

class CreditCardTransaction
  XACTION_DIR = File.join('data', 'cc_xactions')
  
  attr_reader :xaction_id, :cc_ref, :type, :amount, :text
  
  def initialize(xaction_id, cc_ref, type, amount, text)
    @xaction_id, @cc_ref, @type = xaction_id, cc_ref, type
    @amount, @text = amount, text
  end
  
  def self.find_all(cc_ref)
    xactions = []
    input_file = "#{XACTION_DIR}/xactions.xml"
    doc = XML::Document.file(input_file) 
    doc.find('//cc-xactions/cc-xaction').each do |node| 
      if node['cc-ref'] == cc_ref
        xactions << CreditCardTransaction.new(
          node['id'], 
          node['cc-ref'],
          node['type'],
          node['amount'],
          node.find_first('text') 
        )
      end
    end
    xactions
  end
end

credit_card_transaction_controller.rb

<!--
 ! The controller for finding all credit card transactions
 ! 应用的目录为：ccdemo/app/controllers/credit_card_transaction_controller.rb
 -->

class CreditCardTransactionController < ApplicationController
  def show
    @xactions = CreditCardTransaction.find_all(params[:id])
  end
end

show.html.erb

<!--
 ! The View looks as follows
 ! 应用的目录为：ccdemo/app/views/credit_card_transaction/show.html.erb
 -->

<% if @xactions.size == 0 %>
  <p>Currently, there are no transactions.</p>
<% else %>
  <table>
    <tr>
      <th>Transaction ID</th>
      <th>Credit Card Reference</th>
      <th>Amount</th>
      <th>Text</th>
    </tr>
    <% for xaction in @xactions %>
      <tr>
        <td><%= xaction.xaction_id %></td>
        <td><%= xaction.cc_ref %></td>
        <% sign = (xaction.type == 'purchase') ? '+' : '-' %>
        <td><%= sign + number_to_currency(xaction.amount) %></td>
        <td><%= xaction.text %></td>
      </tr>
    <% end %>
  </table>
<% end %>

应用说明： create a Rails application that scans through an XML file containing credit card transactions and displays all transactions belonging to a particular credit card.