ljson

Introduction

This library was educated by Chiron to avenge the crimes against JSON and its heirs in the Erlang world. It is destined to search for the Golden Macro, as revealed by the Cloud Goddess.

Installation

Just add it to your rebar.config deps:

  {deps, [
    ...
    {ljson, ".*",
      {git, "[email protected]:quasiquoting/ljson.git", {tag "0.4.0"}}}
      ]}.

And then do the usual:

    $ rebar3 compile

Usage

The following usage examples are all done from the LFE REPL:

$ lfe -pa _build/default/deps/*/ebin
Erlang/OTP 18 [erts-7.1] [source] [64-bit] [smp:8:8] [async-threads:10] ...

LFE Shell V7.1 (abort with ^G)
>

Encode simple LFE data to JSON:

> (ljson:print (ljson:encode 'a))
<<"\"a\"">>
ok
> (ljson:print (ljson:encode "a"))
<<"[97]">>
ok
> (ljson:print (ljson:encode 1))
<<"1">>
ok
> (ljson:print (ljson:encode 3.14))
<<"3.14">>
ok
> (ljson:print (ljson:encode '(a b c 42)))
<<"[\"a\",\"b\",\"c\",42]">>
ok
> (ljson:print (ljson:encode #(a b)))
<<"{\"a\":\"b\"}">>
ok
> (ljson:print (ljson:encode '(#(a b) #(c d))))
<<"{\"a\":\"b\",\"c\":\"d\"}">>
ok
>

Decode simple JSON:

> (ljson:print (ljson:decode #b("\"a\"")))
<<"a">>
ok

;; ljson can just as easily decode string as binary:
> (ljson:print (ljson:decode "\"a\"")))
<<"a">>
ok

> (ljson:print (ljson:decode #b("[97]")))
"a"
ok
> (ljson:print (ljson:decode #b("1")))
1
ok
> (ljson:print (ljson:decode #b("3.14")))
3.14
ok
> (ljson:print (ljson:decode #b("[\"a\",\"b\",\"c\",42]")))
[<<"a">>,<<"b">>,<<"c">>,42]
ok
> (ljson:print (ljson:decode "{\"a\": \"b\"}"))
{<<"a">>,<<"b">>}
ok
> (ljson:print (ljson:decode "{\"a\":\"b\",\"c\":\"d\"}"))
[{<<"a">>,<<"b">>},{<<"c">>,<<"d">>}]
ok
> (ljson:print
    (ljson:decode
      #B(123 34 97 34 58 34 98 34 44 34 99 34 58 34 100 34 125)))
[{<<"a">>,<<"b">>},{<<"c">>,<<"d">>}]
ok
>

Decode a JSON data structure (note that, for formatting purposes, the data below has been presented separated with newlines; this won't work in the LFE REPL -- you'll need to put it all on one line):

> (set json-data "{
  \"First Name\": \"Jón\",
  \"Last Name\": \"�órson\",
  \"Is Alive?\": true,
  \"Age\": 25,
  \"Height_cm\": 167.6,
  \"Address\": {
    \"Street Address\": \"í Gongini 5 Postsmoga 108\",
    \"City\": \"Tórshavn\",
    \"Country\": \"Faroe Islands\",
    \"Postal Code\": \"100\"
  },
  \"Phone Numbers\": [
    {
      \"Type\": \"home\",
      \"Number\": \"20 60 30\"
    },
    {
      \"Type\": \"office\",
      \"Number\": \"+298 20 60 20\"
    }
  ],
  \"Children\": [],
  \"Spouse\": null}")
> (set data (ljson:decode json-data))
(#(#B(70 105 114 115 116 32 78 97 109 101) #B(74 195 179 110))
 #(#B(76 97 115 116 32 78 97 109 101) #B(195 158 195 179 114 115 111 110))
 #(#B(73 115 32 65 108 105 118 101 63) true)
 #(#B(65 103 101) 25)
 #(#B(72 101 105 103 104 116 95 99 109) 167.6)
 #(#B(65 100 100 114 101 115 115)
   #((#(#B(83 116 114 101 101 116 32 65 100 100 114 101 115 115)
        #B(195 173 32 71 111 110 103 105 110 105 32 53 32 80 111 ...))
      #(#B(67 105 116 121) #B(84 195 179 114 115 104 97 118 110))
      #(#B(67 111 117 110 116 114 121)
        #B(70 97 114 111 101 32 73 115 108 97 110 100 115))
      #(#B(80 111 115 116 97 108 32 67 111 100 101) #B(49 48 48)))))
 #(#B(80 104 111 110 101 32 78 117 109 98 101 114 115)
   (#((#(#B(84 121 112 101) #B(104 111 109 101))
       #(#B(78 117 109 98 101 114) #B(50 48 32 54 48 32 51 48))))
    #((#(#B(84 121 112 101) #B(111 102 102 105 99 101))
       #(#B(78 117 109 98 101 114)
         #B(43 50 57 56 32 50 48 32 54 48 32 50 48))))))
 #(#B(67 104 105 108 100 114 101 110) ())
 #(#B(83 112 111 117 115 101) null))
> (ljson:print data)
[{<<"First Name">>,<<"Jón"/utf8>>},
 {<<"Last Name">>,<<"Þórson"/utf8>>},
 {<<"Is Alive?">>,true},
 {<<"Age">>,25},
 {<<"Height_cm">>,167.6},
 {<<"Address">>,
  {[{<<"Street Address">>,<<"í Gongini 5 Postsmoga 108"/utf8>>},
    {<<"City">>,<<"Tórshavn"/utf8>>},
    {<<"Country">>,<<"Faroe Islands">>},
    {<<"Postal Code">>,<<"100">>}]}},
 {<<"Phone Numbers">>,
  [{[{<<"Type">>,<<"home">>},{<<"Number">>,<<"20 60 30">>}]},
   {[{<<"Type">>,<<"office">>},{<<"Number">>,<<"+298 20 60 20">>}]}]},
 {<<"Children">>,[]},
 {<<"Spouse">>,null}]
ok
>

Now let's take it full circle by encoding it again:

> (ljson:prettify (ljson:encode data))
{
  "First Name": "Jón",
  "Last Name": "Þórson",
  "Is Alive?": true,
  "Age": 25,
  "Height_cm": 167.6,
  "Address": {
    "Street Address": "í Gongini 5 Postsmoga 108",
    "City": "Tórshavn",
    "Country": "Faroe Islands",
    "Postal Code": "100"
  },
  "Phone Numbers": [
    {
      "Type": "home",
      "Number": "20 60 30"
    },
    {
      "Type": "office",
      "Number": "+298 20 60 20"
    }
  ],
  "Children": [],
  "Spouse": null
}
ok
>

Let's do the same, but this time from LFE data:

> (set lfe-data
   `(#(#b("First Name") ,(binary ("Jón" utf8)))
     #(#b("Last Name") ,(binary ("Þórson" utf8)))
     #(#b("Is Alive?") true)
     #(#b("Age") 25)
     #(#b("Height_cm") 167.6)
     #(#b("Address")
      #((#(#b("Street Address") ,(binary ("í Gongini 5 Postsmoga 108" utf8)))
        #(#b("City") ,(binary ("Tórshavn" utf8)))
        #(#b("Country") #b("Faroe Islands"))
        #(#b("Postal Code") #b("100")))))
     #(#b("Phone Numbers")
      (#((#(#b("Type") #b("home")) #(#b("Number") #b("20 60 30"))))
       #((#(#b("Type") #b("office")) #(#b("Number") #b("+298 20 60 20"))))))
     #(#b("Children") ())
     #(#b("Spouse") null)))
(#(#B(...)))
> (ljson:prettify (ljson:encode lfe-data))
{
  "First Name": "Jón",
  "Last Name": "Þórson",
  "Is Alive?": true,
  "Age": 25,
  "Height_cm": 167.6,
  "Address": {
    "Street Address": "í Gongini 5 Postsmoga 108",
    "City": "Tórshavn",
    "Country": "Faroe Islands",
    "Postal Code": "100"
  },
  "Phone Numbers": [
    {
      "Type": "home",
      "Number": "20 60 30"
    },
    {
      "Type": "office",
      "Number": "+298 20 60 20"
    }
  ],
  "Children": [],
  "Spouse": null
}
ok

Extract elements from the original converted data structure as well as our LFE data structure we just entered directly, above:

> (ljson:print (ljson:get '("First Name") data))
<<"Jón"/utf8>>
ok
> (ljson:print (ljson:get '("Address" "City") data))
<<"Tórshavn"/utf8>>
ok
> (ljson:print (ljson:get '("Phone Numbers" 1 "Type") data))
<<"home">>
ok
> (ljson:print (ljson:get '("First Name") lfe-data))
<<"Jón"/utf8>>
ok
> (ljson:print (ljson:get '("Address" "City") lfe-data))
<<"Tórshavn"/utf8>>
ok
> (ljson:print (ljson:get '("Phone Numbers" 1 "Type") lfe-data))
<<"home">>
ok

You may also use atom or binary keys:

> (ljson:print (ljson:get '(|Phone Numbers| 1 Number) lfe-data))
<<"20 60 30">>
ok
> (ljson:print (ljson:get '(#b("Phone Numbers") 1 #b("Number")) lfe-data))
<<"20 60 30">>
ok

Extract elements directly from JSON:

> (ljson:print (ljson:get '("First Name") json-data #(json)))
<<"\"J\\u00c3\\u00b3n\"">>
ok
> (ljson:print (ljson:get '("Address" "City") json-data #(json)))
<<"\"T\\u00c3\\u00b3rshavn\"">>
ok
> (ljson:print (ljson:get '("Phone Numbers" 1 "Type") json-data #(json)))
<<"\"home\"">>
ok

Under the Deck

The Argonauts that are rowing this thing consist of the following:

• mochijson2 - for encoding
• jsx - for decoding, prettify and minify
• dict - (wrapped as pairs) for large key/value lists
• proplists/lists of tuples - for small key/value lists