jason 
jason is a JSON encode/decode library written in Erlang.
Overview
This project was mainly created for easy handling of JSON from/to Erlang records, but allow binary struct, proplists and maps formats.
Project is available on hex.pm under name jason_erl.
jason offer also a rare feature : pretty printing JSON in several indentation styles.
See Wiki for documentation and tutorial.
Specifications
- Pure Erlang (no NIF)
- Decoding use Leex/Yecc parser
- JSON object can be decoded in several formats :
- binary struct
- proplists
- maps
- records with automatic ad hoc module loaded for record handling
- No
parse_transform. Record definitions can be given as arguments or extracted from module(s) abstract code at runtime.
Data types
jason:types/0 show in console how Erlang types are converted to JSON and back to Erlang data.
1> jason:types().
Erlang JSON Erlang
================================================================================
%% Atoms
null -> null -> null
undefined -> null -> null
true -> true -> true
false -> false -> false
any -> "any" -> <<"any">>
%% Integer
123 -> 123 -> 123
%% Float (Automatic precision)
123.456789 -> 123.456789 -> 123.456789
2.30e+0 -> 2.3 -> 2.3
2.30e+3 -> 2300.0 -> 2.3e3
2.30e-3 -> 0.0023 -> 0.0023
%% List
[1,2,3] -> [1,2,3] -> [1,2,3]
[a,"b",<<"c">>] -> ["a","b","c"] -> [<<"a">>,<<"b">>,<<"c">>]
%% Date
{{1970,1,1},{0,0,0}} -> "1970-01-01T00:00:00Z" -> {{1970,1,1},
{0,0,0}}
{{1970,1,1},{0,0,0.0}} -> "1970-01-01T00:00:00.000Z" -> {{1970,1,1},
{0,0,0.0}}
%% Binary (key/value) mode=struct (default)
<<"abc">> -> "abc" -> <<"abc">>
%% Struct
% mode=struct (default)
{<<"abc">>,<<"def">>} -> {"abc": "def"} -> [{<<"abc">>,<<"def">>}]
% mode=proplist
{<<"abc">>,<<"def">>} -> {"abc": "def"} -> [{abc,"def"}]
% mode=map
{<<"abc">>,<<"def">>} -> {"abc": "def"} -> #{abc => "def"}
% mode=record
{<<"abc">>,<<"def">>} -> {"abc": "def"} -> {'111259705',"def"}
with -record('111259705', {abc = [] :: list()}).
%% Proplist
% mode=struct (default)
[{abc,<<"def">>}] -> {"abc": "def"} -> [{<<"abc">>,<<"def">>}]
% mode=proplist
[{abc,<<"def">>}] -> {"abc": "def"} -> [{abc,"def"}]
% mode=map
[{abc,<<"def">>}] -> {"abc": "def"} -> #{abc => "def"}
% mode=record
[{abc,<<"def">>}] -> {"abc": "def"} -> {'111259705',"def"}
with -record('111259705', {abc = [] :: list()}).
%% Map
% mode=struct (default)
#{"abc" => <<"def">>} -> {"abc": "def"} -> [{<<"abc">>,<<"def">>}]
% mode=proplist
#{"abc" => <<"def">>} -> {"abc": "def"} -> [{abc,"def"}]
% mode=map
#{"abc" => <<"def">>} -> {"abc": "def"} -> #{abc => "def"}
% mode=record
#{"abc" => <<"def">>} -> {"abc": "def"} -> {'111259705',"def"}
with -record('111259705', {abc = [] :: list()}).
%% Record - encoding using option [{records, [{r, record_info(fields, r)}]}] or [{records, [{r, [k1,k2]}]}]
% mode=struct (default)
{r,1,<<"ab">>} -> {"k1": 1,"k2": "ab"} -> [{<<"k1">>,1},
{<<"k2">>,<<"ab">>}]
% mode=proplist
{r,1,<<"ab">>} -> {"k1": 1,"k2": "ab"} -> [{k1,1},{k2,"ab"}]
% mode=map
{r,1,<<"ab">>} -> {"k1": 1,"k2": "ab"} -> #{k1 => 1,k2 => "ab"}
% mode=record
{r,1,<<"ab">>} -> {"k1": 1,"k2": "ab"} -> {'8056669',1,"ab"}
with -record('8056669', {k1 = 0 :: integer(), k2 = [] :: list()}).
% mode=record - decoding using option [{records, [{r, [k1,k2]}]}]
-> {r,1,"ab"}
