BsonUser Guide


Bson is an implementation of the BSON specification complete with BSON serialisation and deserialisation.

Note that BSON is an extention of JSON, and JSON can only represent a subset of the types supported by BSON.

Bson was created to support the development of the Alien-Factory MongoDB driver.

Quick Start

1). Create a text file called

using afBson

class Example {

  Void main() {
    buf := Buf()

    documentIn := [
      "_id"  : ObjectId(),
      "name" : "Dave",
      "age"  : 42

    // serialise BSON to a stream

    // deserialise BSOM from a stream
    documentOut := BsonReader(


2). Run as a Fantom script from the command line:

C:\> fan

[_id:53503531a8000b8b44000001, name:Dave, age:42]


The main BsonReader and BsonWriter classes (de)serialise BSON objects to and from Fantom using the following mapping:

-   Fantom           BSON       -
afBson::Binary    -> BINARY
   sys::Bool      -> BOOLEAN
afBson::Code      -> CODE
afBson::Code      -> CODE_W_SCOPE
   sys::DateTime  -> DATE
   sys::Float     -> DOUBLE
   sys::Int       -> INTEGER_64
   sys::List      -> ARRAY
   sys::Map       -> DOCUMENT
afBson::MaxKey    -> MAX_KEY
afBson::MinKey    -> MIN_KEY
        null      -> NULL
afBson::ObjectId  -> OBJECT_ID
   sys::Regex     -> REGEX
   sys::Str       -> STRING
afBson::Timestamp -> TIMESTAMP

Note that the deprecated BSON constructs UNDEFINED, DB_POINTER and SYMBOL are ignored and have no Fantom representation.

Bson takes care of all the tricky Endianness. All BSON objects (except for Buf) may be serialised to and from strings using Fantom's standard serialisation techniques.

CAUTION: INTEGER_32 values will be read as Int values. If you then write its containing document, the storage type will be converted to INTEGER_64.

This is only of concern if other, non Fantom, drivers have written INTEGER_32 values to the database.

CAUTION: Fantom does not support regex flags. When reading a BSON regex, flags are convered into embedded characted flags. e.g. /myregex/im is converted into /(?im)myregex/. See Java's Pattern class for a list of supported flags (dimsuxU).

Again, this is only of concern if other, non Fantom, drivers have written REGEX values (with flags) to the database.

The Alien-Factoy BSON library was inspired by fantomongo by Liam Staskawicz.