add_plugin.rb

require 'rexml/document'

PLUGIN_PATH = 'project/build/plugins/plugin'
ARTIFACT_PATH = 'artifactId'
COMPILER_NAME = 'maven-compiler-plugin'
NEW_PLUGIN = "<plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                  <source>1.6</source>
                  <target>1.6</target>
                </configuration>
              </plugin>"

def get_file_list(dir)
  Dir.glob("#{dir}/**/pom.xml")
end

def get_xml(pom)
  file = File.open(pom)
  REXML::Document.new(file)
end

def save_xml(file_name, xml)
  File.open(file_name, 'w') do |file|
    file.puts(xml)
  end
  # puts file_name
  # puts xml
end

def is_compiler?(plugin)
  artifacts = []
  plugin.elements.each(ARTIFACT_PATH) do |artifact|
    artifacts << artifact.text
  end
  artifacts[0] == COMPILER_NAME
end

def update_xml(xml)
  new_plugin = REXML::Document.new(NEW_PLUGIN)
  xml.root.insert_before("//plugin", new_plugin)
  xml
end

def fix(pom)
  good = false
  myxml = get_xml(pom)
  myxml.elements.each(PLUGIN_PATH) do |plugin|
    good = true if is_compiler?(plugin)
  end
  save_xml(pom, update_xml(myxml)) unless good
end

poms = get_file_list(ARGV[0])
poms.each do |pom|
  begin
    fix(pom)
  rescue Exception => e
    # puts "Error updating #{pom}"
    # puts e.message
    # puts e.backtrace.inspect
  end
end