eJSONPath is pure-erlang implementation of JSONPath.
It uses jiffy JSON structure ({[ {key(), value()}, ...]} for structs) and implements most of the
JSONPath description (I don't say specification, because there is no such thing like jsonpath spec).
- Robust extensible parser (leex + yecc).
- Extensible by custom functions.
- No dependencies (but you may want jiffy as json parser).
{ok, Bin} = file:read_file("test/doc.json").
Doc = jiffy:decode(Bin).
%% return 1'st book author
[<<"Nigel Rees">>] = ejsonpath:execute("$.store.book[0].author", Doc).
%% return 1'st book categody and author
[<<"reference">>,
<<"Nigel Rees">>] = ejsonpath:execute("$.store.book[0]['category','author']", Doc).
%% return only reference book authors
%% `Funs' is a list of `{Name, Fun}' pairs (see Fun spec on sources)
Funs = [
{<<"filter_category">>,
fun({{Pairs}, _Doc}, [CategoryName]) ->
case proplists:get_value(<<"category">>, Pairs) of
CategoryName -> true;
_ -> false
end
end}
],
[<<"Nigel Rees">>] = ejsonpath:execute(
"$.store.book[?(filter_category('reference'))].author", Doc, Funs).More examples in tests.
Since there is no such thing as JSONPath specification, every implementer create it's own variations. But I try to follow description from JSONPath as close as possible.
+-----------------------+---------------------+-----------+
| Feature | Example |Implemented|
+-----------------------+---------------------+-----------+
|Dot filtering |`$.one.two` | Y |
+-----------------------+---------------------+-----------+
|Brace filtering |`$['one']['two']` | Y |
+-----------------------+---------------------+-----------+
|Array slicing | `$[1,2,3]` `$.o[2]` | Y |
+-----------------------+---------------------+-----------+
|Hash slicing | `$['one', 'two']` | Y |
+-----------------------+---------------------+-----------+
|Asterisk (hash, array) | `$.one.*` `$.one[*]`| Y |
+-----------------------+---------------------+-----------+
|Python-slicing | `$[1:-1:2]` | Partial* |
+-----------------------+---------------------+-----------+
|Eval binary filter | `$[?(true)]` | Partial** |
+-----------------------+---------------------+-----------+
|Eval index | `$[('one')]` | Partial** |
+-----------------------+---------------------+-----------+
|Recursive descent | `..` | N |
+-----------------------+---------------------+-----------+
* Only step=1 supported now
** Very limited scripting language: string, integer and function calls
Most of the missing features can be implemented as custom functions
$.one[?( custom_function_call('arg1', 42) )]
$.two[( custom_function_call() )]
- Implement missing features
- Python slicing step support. (Currently only step==1 supported)
- Recursive descent (supported by parser, need evaluator)
- Eval filter / index - allow path expressions and operators
$[?(@.category)] - Eval filter / index - allow binary operators
$[?(@.category!='reference')] - Support for alternative JSON representations (mochijson2, EEP-18)
- GeneStevens/jsonpath - very simple Erlang implementation.
Support only dot-keys and integer indexes
one[0].two.three. - Reference JS implementation Reference implementation. Implemented as mix of regexps and javascript eval's.
- Java implementaion - powerfull Java implementation
- Limited python impl - limited Python implementation
- Online evaluator - realy useful only with patch
window.dump = function(v) { return JSON.stringify(v, null, " ") }
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