XML

Contents 1 References 2 REXML 2.1 Simple Example: parse whole file at once 2.2 Simple Example: change data and output 2.3 Stream parsing 2.4 Stream parsing, change attributes 2.5 SAX 2 parsing

References

• REXML Tutorial with lots of examples
• REXML API

REXML

Simple Example: parse whole file at once

This example is appropriate for small files only. Stream parsing is a necessity for larger XML files.

require "rexml/document"
file = File.new( ARGV[0] )
doc = REXML::Document.new file
doc.elements.each('html/body/a') do |e|
    puts e.attributes["href"]
end

Simple Example: change data and output

...
doc.elements.each('html/body/a') do |e|
    e.attributes["href"] = "http://whatever.org/"
end
doc.write $stdout

Stream parsing

Stream parsing must be used for larger XML files. This example outputs the 'href'-attribute of all 'a' tags.

require "rexml/document"
require "rexml/streamlistener"
class MyListener
    include REXML::StreamListener
    def tag_start(name, attrs)
        case name
        when "a"
            puts attrs["href"]
        end
    end
end
file = File.new( ARGV[0] )
REXML::Document.parse_stream(file,MyListener.new)

Stream parsing, change attributes

This is example could be used as a template for a program that outputs a copy of the input stream, but with certain attributes changed.

class MyListener
    include REXML::StreamListener
    def tag_start(name, attrs)
        case name
        when "a"
            ...
        else
        end
        e = REXML::Element.new(name)
        attrs.each do |att, value| 
            e.attributes[att] = value
        end
        puts e.to_s.sub(/\/>/, '>')
    end
    def tag_end(name)
        puts REXML::Element.new(name).to_s.sub(/<(.*)\/>/, '</\1>')
    end
end

SAX 2 parsing

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