Two phase commit for Couchbase. Version 2 (improved version of https://gist.github.com/3135796)

test.rb

require 'rubygems'
require 'couchbase'

def transfer(source, destination, amount)
  cb = Couchbase.bucket

  # prepare transaction document
  id = cb.incr("transaction:counter", :create => true)
  trans_id = "transaction:#{id}"
  cb.set(trans_id, {"source" => source, "destination" => destination,
         "amount" => amount, "state" => "initial"})

  # STEP 1: Switch transaction into pending state
  cb.cas(trans_id) do |val|
    val.update("state" => "pending")
  end

  # STEP 2: Apply transaction to both documents
  cb.cas(source) do |val|
    val.update("points" => val["points"] - amount,
               "transactions" => val["transactions"] + [trans_id])
  end
  cb.cas(destination) do |val|
    val.update("points" => val["points"] + amount,
               "transactions" => val["transactions"] + [trans_id])
  end

  # STEP 3: Switch transaction into committed state
  cb.cas(trans_id) do |val|
    val.update("state" => "committed")
  end

  # STEP 4: Remove transaction from the documents
  cb.cas(source) do |val|
    val.update("transactions" => val["transactions"] - [trans_id])
  end
  cb.cas(destination) do |val|
    val.update("transactions" => val["transactions"] - [trans_id])
  end

  # STEP 5: Switch transaction into done state
  cb.cas(trans_id) do |val|
    val.update("state" => "done")
  end
rescue Couchbase::Error::Base => ex
  # Rollback transaction
  trans, flags, cas = cb.get(trans_id, :extended => true)
  case trans["state"]
  when "committed"
    # Create new transaction and swap the targets
    transfer(destination, source, amount)
  when "pending"
    # STEP 1: Switch transaction into cancelling state
    cb.set(trans_id, val.update("state" => "cancelling"),
           :flags => flags, :cas => cas)

    # STEP 2: Revert changes if they were applied
    cb.cas(source) do |val|
      break unless val["transactions"].include?(trans_id)
      val.update("points" => val["points"] + 100,
                 "transactions" => val["transactions"] - [trans_id])
    end
    cb.cas(destination) do |val|
      break unless val["transactions"].include?(trans_id)
      val.update("points" => val["points"] - 100,
                 "transactions" => val["transactions"] - [trans_id])
    end

    # STEP 3: Switch transaction into cancelled state
    cb.cas(trans_id) do |val|
      val.update("state" => "cancelled")
    end
  end

  # Re-raise original exception
  raise ex
end

cb = Couchbase.bucket

# preload initial documents
cb.set("karen", {"name" => "karen", "points" => 500, "transactions" => []})
cb.set("dipti", {"name" => "dipti", "points" => 700, "transactions" => []})

transfer("karen", "dipti", 100)

Is there a equivalent example in Java?

Is there a equivalent example in Java?