Easily convert a MongoDB BSON file to JSON with Ruby

bson2json.rb

#!/usr/bin/ruby

# This script acts as a command-line filter to convert a BSON file (such as from mongodump) to an equivalent JSON file
# The resulting JSON file will be an array of hashes
# Any binary values from the BSON file are converted to base64 (such as Mongo's _id fields)
# I originally wrote this script so that Mongo files can be easily used with jsawk for
# offline data processing -- https://github.com/micha/jsawk
#
# To invoke, assuming mycollection.bson is a file from mongodump:
#   ruby bson2json.rb  < mycollection.bson > mycollection.json

require 'rubygems'
require 'bson'
require 'json'
require 'base64'

def process(file)
  puts '['
  
  while not file.eof? do
    bson = BSON.read_bson_document(file)
    bson = bson_debinarize(bson)
    puts bson.to_json + (file.eof? ? '' : ',')
  end
  
  puts ']'
end

# Accept BSON document object; return equivalent, but with any BSON::Binary values converted with Base64
def bson_debinarize(bson_doc)
  raise ArgumentError, "bson_doc must be a BSON::OrderedHash" unless bson_doc.is_a?(BSON::OrderedHash)
  
  # each key and value is passed by reference and is modified in-place
  bson_doc.each do |k,v|
    if v.is_a?(BSON::Binary)
      bson_doc[k] = Base64.encode64(v.to_s)
    elsif v.is_a?(BSON::OrderedHash)
      bson_doc[k] = bson_debinarize(v)
    end
  end
  
  bson_doc 
end

process(STDIN)

__END__

Copyright (c) 2012 SPARC, LLC

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