#to run the server

rbenv shell jruby-1.6.5
gem install excel_builder
cd $(gem which excel_builder | xargs dirname)/../ext
bundle --version || gem install bundler
bundle install
ruby app.rb

#to use the client

rbenv shell 1.9.2-p290
gem install excel_builder

irb
require 'rubygems'
require 'excel_builder'
ExcelBuilder::Connector.site = 'http://localhost:4567'
File.open('test.xlsx', 'w') do |f|
  file_contents = ExcelBuilder::Connector.generate_xlsx('text.xlsx') do |workbook|
    sheet = workbook.worksheets['hello']
    sheet.rows[0][0].value = 4.0
  end
  f.write file_contents
end