Parsing JSON in Erlang

问题:

I have a piece of JSON string, which I want to parse in Erlang. It looks like:

({ id1 : ["str1", "str2", "str3"], id2 : ["str4", "str5"]})

I looked at mochijson2, and a couple of other JSON parsers, but I really could not figure out how to do it. Any help greatly appreciated!

回答1:

I once used the erlang-json-eep-parser, and tried it on your data.

7> json_eep:json_to_term("({ id1 : [\"str1\", \"str2\", \"str3\"], id2 : [\"str4\", \"str5\"]})").
** exception error: no match of right hand side value 
                    {error,{1,json_lex2,{illegal,"("}},1}
     in function  json_eep:json_to_term/1

Right, it doesn't like the parentheses.

8> json_eep:json_to_term("{ id1 : [\"str1\", \"str2\", \"str3\"], id2 : [\"str4\", \"str5\"]}").
** exception error: no match of right hand side value 
                    {error,{1,json_lex2,{illegal,"i"}},1}
     in function  json_eep:json_to_term/1

And it doesn't like the unquoted keys:

18> json_eep:json_to_term("{ \"id1\" : [\"str1\", \"str2\", \"str3\"], \"id2\" : [\"str4\", \"str5\"]}").
{[{<<"id1">>,[<<"str1">>,<<"str2">>,<<"str3">>]},
  {<<"id2">>,[<<"str4">>,<<"str5">>]}]}

That looks better.

So it seems that your data is almost JSON, at least as far as this parser is concerned.

回答2:

you can work on your JSON at the JSONLint validator: http://www.jsonlint.com/

回答3:

Have you looked at http://www.json.org/ ?

or download "json4erlang" from here: json-and-json-rpc-for-erlang

回答4:

Your input is not quite JSON -- the keys need to be quoted, like this:

{ "id1" : ["str1", "str2", "str3"], "id2" : ["str4", "str5"]}

A good Erlang library for manipulating JSON is jsx

回答5:

Your JSON keys are not valid according to https://www.ietf.org/rfc/rfc4627.txt. Once you correct it, there are plenty of JSON libraries for Erlang, my favorite is JSX(https://github.com/talentdeficit/jsx/):

MyJSON = { "id1" : ["str1", "str2", "str3"], "id2" : ["str4", "str5"]},
jsx:decode(MyJSON, [return_maps]).

And it will return an Erlang map data structure that can be manipulated to your needs http://learnyousomeerlang.com/maps