LibXML Ruby

Overview

The libxml gem provides Ruby language bindings for GNOME’s Libxml2 XML toolkit. It is free software, released under the MIT License.

libxml-ruby provides several advantages over REXML:

Speed - libxml is many times faster than REXML
Features - libxml provides a number of additional features over REXML, including XML Schema Validation, RelaxNg validation, xslt (see libxslt-ruby)
Conformance - libxml passes all 1800+ tests from the OASIS XML Tests Suite

Requirements

libxml-ruby requires Ruby 1.8.4 or higher. It is dependent on the following libraries to function properly:

libm (math routines: very standard)
libz (zlib)
libiconv
libxml2

If you are running Linux or Unix you’ll need a C compiler so the extension can be compiled when it is installed. If you are running Windows, then install the Windows specific RubyGem which includes an already built extension.

INSTALLATION

The easiest way to install libxml-ruby is via Ruby Gems. To install:

gem install libxml-ruby

If you are running Windows, make sure to install the Win32 RubyGem which includes an already built binary file. The binary is built against libxml2 version 2.6.32 and iconv version 1.12. Both of these are also included as pre-built binaries, and should be put either in the libxml/lib directory or on the Windows path.

The Windows binaries are biult with MingW. The gem also includes a Microsoft VC++ 2005 solution. If you wish to run a debug version of libxml-ruby on Windows, then it is highly recommended you use VC++.

Functionality

libxml is a highly conformant XML parser, passing all 1800+ tests from the OASIS XML Tests Suite. In addition, it includes rich functionality such as:

SAX
DOM
XMLReader
XPath
XPointer
XML Schema
DTDs
XSLT (split into the libxslt-ruby bindings)

libxml-ruby provides impressive coverage of libxml’s functionality through an easy-to-use C api.

Performance

In addition to being feature rich and conformation, the main reason people use libxml-ruby is for performance. Here are the results of a couple simple benchmarks recently blogged about on the Web (you can find them in the benchmark directory of the libxml distribution).

From depixelate.com/2008/4/23/ruby-xml-parsing-benchmarks

               user     system      total        real
 libxml    0.032000   0.000000   0.032000 (  0.031000)
 Hpricot   0.640000   0.031000   0.671000 (  0.890000)
 REXML     1.813000   0.047000   1.860000 (  2.031000)

From svn.concord.org/svn/projects/trunk/common/ruby/xml_benchmarks/

               user     system      total        real
 libxml    0.641000   0.031000   0.672000 (  0.672000)
 hpricot   5.359000   0.062000   5.421000 (  5.516000)
 rexml    22.859000   0.047000  22.906000 ( 23.203000)

USAGE

For in-depth information about using libxml-ruby please refer to its online Rdoc documentation. Some simple examples are shown below.

READING

There are several ways to read xml documents.

  require 'libxml'
  doc = XML::Document.file('output.xml')
  root = doc.root

  puts "Root element name: #{root.name}"

  elem3 = root.find('elem3').to_a.first
  puts "Elem3: #{elem3['attr']}"

  doc.find('//root_node/foo/bar').each do |node|
    puts "Node path: #{node.path} \t Contents: #{node.content}"
  end

And your terminal should look like:

  Root element name: root_node
  Elem3: baz
  Node path: /root_node/foo/bar[1]         Contents: 1
  Node path: /root_node/foo/bar[2]         Contents: 2
  Node path: /root_node/foo/bar[3]         Contents: 3
  Node path: /root_node/foo/bar[4]         Contents: 4
  Node path: /root_node/foo/bar[5]         Contents: 5
  Node path: /root_node/foo/bar[6]         Contents: 6
  Node path: /root_node/foo/bar[7]         Contents: 7
  Node path: /root_node/foo/bar[8]         Contents: 8
  Node path: /root_node/foo/bar[9]         Contents: 9
  Node path: /root_node/foo/bar[10]        Contents: 10

WRITING

To write a simple document:

  require 'libxml'

  doc = XML::Document.new()
  doc.root = XML::Node.new('root_node')
  root = doc.root

  root << elem1 = XML::Node.new('elem1')
  elem1['attr1'] = 'val1'
  elem1['attr2'] = 'val2'

  root << elem2 = XML::Node.new('elem2')
  elem2['attr1'] = 'val1'
  elem2['attr2'] = 'val2'

  root << elem3 = XML::Node.new('elem3')
  elem3 << elem4 = XML::Node.new('elem4')
  elem3 << elem5 = XML::Node.new('elem5')

  elem5 << elem6 = XML::Node.new('elem6')
  elem6 << 'Content for element 6'

  elem3['attr'] = 'baz'

  format = true
  doc.save('output.xml', format)

The file output.xml contains:

  <?xml version="1.0"?>
  <root_node>
    <elem1 attr1="val1" attr2="val2"/>
    <elem2 attr1="val1" attr2="val2"/>
    <elem3 attr="baz">
      <elem4/>
      <elem5>
        <elem6>Content for element 6</elem6>
      </elem5>
    </elem3>
    <foo>
      <bar>1</bar>
      <bar>2</bar>
      <bar>3</bar>
      <bar>4</bar>
      <bar>5</bar>
      <bar>6</bar>
      <bar>7</bar>
      <bar>8</bar>
      <bar>9</bar>
      <bar>10</bar>
    </foo>
  </root_node>

DOCUMENTATION

RDoc comments are included - run ‘rake doc’ to generate documentation. You can find the latest documentation at:

libxml.rubyforge.org/rdoc/

License

See LICENSE for license information.

MORE INFORMATION

For more information please refer to the documentation. If you have any questions, please send email to libxml-devel@rubyforge.org.

README