Demonstrate how to use Drb to integrate to Java through Ruby and JRuby

client.rb

# ruby client.rb SheetName > output.xls

require 'drb/drb'

SERVER_URI="druby://localhost:8787"
DRb.start_service
service = DRbObject.new_with_uri(SERVER_URI)
puts service.get_excel_output('sheet_name' => ARGV.first || 'Test')

excel_exporter.rb

# run with JRuby
require 'java'
require_relative 'lib/poi-3.7.jar'

import java.io.ByteArrayOutputStream
import org.apache.poi.hssf.usermodel.HSSFWorkbook

class ExcelExporter
  def initialize(data)
    @wb = HSSFWorkbook.new
    @sheet = @wb.create_sheet(data['sheet_name'])
  end

  def out
    os = ByteArrayOutputStream.new
    @wb.write os
    String.from_java_bytes(os.to_byte_array)
  end
end

server.rb

require 'drb/drb'
require_relative 'excel_exporter'

URI="druby://localhost:8787"

class Service
  def get_excel_output(data)
    ExcelExporter.new(data).out
  end
end

DRb.start_service URI, Service.new

puts "Listening on #{URI}"
# Wait for the drb server thread to finish before exiting.
DRb.thread.join