Re: Ruby and XML

On Sep 5, 2011, at 5:42 PM, Bob Aiello wrote:
> Essentially, I have hundreds of XML files like this one that contain
> many many name value pairs. I am concerned that the value is defined
> differently (actually I have seen this) in one or more of the XML. I
> want to take an xml file and then parse the name/value pairs into a
> list. Then I want to check that list against all of the other XML in the
> system that have the same name/value pairs.

For your consideration, below is how I would write a script to handle this. It creates a Hash storing names and key/value pairs; when the same key is seen again with a new value, it keeps track of all values seen as an array. The "SourceFile" module associates with each value string the file that it was defined in, so that you can later see where the values were defined. Use a module for this is both tricky 

### collider.rb
    require 'nokogiri'

    # Perhaps use Marshal to load this from a file if it exists,
    # and save out the values seen so far at the end of the run.
    $all_values = {}

    # Find your file(s) to analyze however you want here
    files = %w[ my.xml ]

    module SourceFile
      attr_accessor :source_file
    end

    files.each do |file|
      doc = Nokogiri::XML(IO.read(file))
      doc.remove_namespaces!

      # Find every <name> that has a <value> sibling
      doc.xpath('//property/name[following-sibling::value]').each do |name|
        value = name.at_xpath('following-sibling::value').text
        # Record where this value came from
        value.extend(SourceFile); value.source_file = file

        name  = name.text
        if $all_values.key?(name)
          old = $all_values[name]
          unless old==value
            warn "#{name} is #{old.inspect} and #{value.inspect}"
            $all_values[name] = [*old,value]
          end
        else
          $all_values[name] = value
        end
      end
    end
    #=> core.app.root is "myroot" and "bigroot"
    #=> core.app.root is ["myroot", "bigroot"] and "sarsaparilla root"

    # Print any keys that point to an array of values...
    $all_values.select{ |key,val| val.is_a?(Array) }.each do |key,values|
      puts "#{key}:"
      puts values.map{ |v| "%20s: '%s'" % [v.source_file,v] }
    end
    #=> core.app.root:
    #=>               my.xml: 'myroot'
    #=>               my.xml: 'bigroot'
    #=>               my.xml: 'sarsaparilla root'

### my.xml
    <?xml version="1.0" encoding="UTF-8"?>
    <product-state xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns="urn://mycompany.com/ia/product-state" xsi:type="product-state">
      <properties>
        <!-- WebSphere properties -->
        <property>
          <name>core.was.home</name>
          <value>/usr/IBM/WebSphere/AppServer1/profiles/AppSrvQA</value>
        </property>
        <property>
          <name>core.was.username</name>
          <value>admin</value>
        </property>
        <property>
          <name>core.was.password</name>
          <value>password</value>
        </property>
        <property>
          <name>core.application.name</name>
          <value>myapp</value>
        </property>
        <property>
          <name>core.app.root</name>
          <value>myroot</value>
        </property>
        <property>
          <name>core.app.root</name>
          <value>bigroot</value>
        </property>
        <property>
          <name>core.was.password</name>
          <value>password</value>
        </property>
        <property>
          <name>core.app.root</name>
          <value>sarsaparilla root</value>
        </property>
      </properties>
    </product-state>