Ruby Jing

RELAX NG schema validation using Jing

Overview

require "jing"

jing = Jing.new(options)
begin
  errors = jing.validate(rngpath, xmlpath)
rescue Jing::OptionError, Jing::ExecutionError => e
  abort "what what what #{e}"
end

if errors.none?
  puts "Valid!"
else
  errors.each do |error|
    puts "#{error[:message]} @ #{error[:line]}:#{error[:column]}"
  end
end

Why use Java to validate instead of Ruby libraries like Nokorigi, REXML, libxml, etc..?

Simple: good error messages. Let's look at the error messages provided by each of these libraries.

<!-- RNG schema -->
<element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0">
  <zeroOrMore>
    <element name="card">
      <attribute name="version">
        <choice>
          <value>v1</value>
          <value>v2</value>
        </choice>
      </attribute>
      <element name="name">
        <text/>
      </element>
    </element>
  </zeroOrMore>
</element>

<!-- XML A -->
<addressBook>
  <card></card>
</addressBook>

<!-- XML B -->
<addressBook>
  <card verison="v100">    
    <name>John Smith</name>
    <oops>Doh!</oops>
  </card>
</addressBook>

Nokorigi/libxml

schema = Nokogiri::XML::RelaxNG(rng)
doc = Nokogiri::XML(xml)
errors = schema.validate(doc)  
errors.each { |e| puts e }

Resulting errors:

# XML A
Element card failed to validate attributes
Expecting an element , got nothing

# XML B
Element card failed to validate attributes
Did not expect element oops there

REXML

include REXML
doc = Document.new(File.read(xml))
validator = Validation::RelaxNG.new(File.read(rng))
validator.validate(doc)

Fails for XML A and XML B –it treats the XML declaration as a validation error!

Validation error.  Expected: :start_element( addressBook ) from < S.1 #:start_element( addressBook ), < Z.2 #:start_element( card ), :start_attribute( version ), < C.3 :text( v1 ) or :text( v2 ) >, :end_attribute(  ), :start_element( name ), :text(  ), :end_element(  ), :start_element( email ), :text(  ), :end_element(  ), :end_element(  ) >, :end_element(  ), :end_document(  ) >  but got <?xml ... ?>( 
 )

Jing

jing = Jing.new
errors = jing.validate(rng, xml)
errors.each { |e| puts e[:error] }

Resulting errors:

# XML A
element "card" missing required attribute "version"
element "card" incomplete; missing required element "name"

# XML B
value of attribute "version" is invalid; must be equal to "v1" or "v2"
element "oops" not allowed anywhere; expected the element end-tag

Better, don't ya think?

More Info

Author

Skye Shaw [skye.shaw AT gmail.com]

License

Released under the MIT License: www.opensource.org/licenses/MIT

Jing Copying Conditions

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