Jaxon :zap:

Jaxon is the fastest JSON parser that can stream any JSON document without holding it all in memory.

Jaxon fully conforms to the RFC 8259 and ECMA 404 standards and is tested against JSONTestSuite.

Roadmap:

Make an alternative parser in Elixir, for those who don't want to use NIFs.
JSON events to string Encoder.

Installation

def deps do
  [
    {:jaxon, "~> 1.0"}
  ]
end

Simple decoding

Decode a binary:

iex> Jaxon.decode(~s({"jaxon":"rocks","array":[1,2]}))
{:ok, %{"array" => [1, 2], "jaxon" => "rocks"}}

iex> Jaxon.decode!(~s({"jaxon":"rocks","array":[1,2]}))
%{"array" => [1, 2], "jaxon" => "rocks"}

Streaming

Query a binary JSON stream:

iex> stream = [~s({"jaxon":"rocks","array":[1,2]})]
iex> stream |> Jaxon.Stream.query([:root, "array", :all]) |> Enum.to_list()
[1, 2]

Query a binary JSON stream using JSON path expressions:

iex> stream = [~s({"jaxon":"rocks","array":[1,2]})]
iex> stream |> Jaxon.Stream.query(Jaxon.Path.decode!("$.array[*]")) |> Enum.to_list()
[1, 2]

Query a large file without holding the whole file in memory:

"large_file.json"
|> File.stream!()
|> Jaxon.Stream.query([:root, "users", :all, "id"])
|> Enum.to_list()

Events

Everything that Jaxon does is based on parsed JSON events like these:

:start_object
:end_object
:start_array
:end_array
{:string, binary}
{:integer, integer}
{:decimal, float}
{:boolean, boolean}
nil
{:incomplete, binary}
{:error, binary}
:colon
:comma
:end

Which make it very flexible when decoding files and lets us use different implementations for parsers, at the moment the default parser is written in C as a NIF.

config :jaxon, :parser, Jaxon.Parsers.NifParser # only NifParser is supported at the moment

The parser takes a binary and returns a list of events:

iex> Jaxon.Parser.parse(~s({"key":2}))
[:start_object, {:string, "key"}, :colon, {:integer, 2}, :end_object, :end]

Which means that it can also parse a list of JSON tokens, event if the string is not a valid JSON representation:

iex> Jaxon.Parser.parse(~s("this is a string" "another string"))
[{:string, "this is a string"}, {:string, "another string"}, :end]

Nif parser

The NIF parser is in C and all it does is take a binary and return a list of JSON events, the NIF respects the Erlang scheduler and tries to run for a maximum of one millisecond, yielding to the VM for another call if it runs over the limit.

Benchmarks

Jaxon (using the NIF parser) performance is similar and often faster than jiffy and jason.

To run the benchmarks, execute:

mix bench.decode

License

Copyright © 2018 Mohamed Boudra <mohamed@boudra.me>

This project is under the Apache 2.0 license. See the LICENSE file for more details.

Developed at Sqlify.io for big data JSON parsing.