Provided by: libjson-path-perl_0.431-1_all 
NAME
JSON::Path::Evaluator - A module that recursively evaluates JSONPath expressions with
native support for Javascript-style filters
VERSION
version 0.431
SYNOPSIS
use JSON::MaybeXS qw/decode_json/; # Or whatever JSON thing you like. I won't judge.
use JSON::Path::Evaluator qw/evaluate_jsonpath/;
my $obj = decode_json(q(
{ "store": {
"book": [
{ "category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{ "category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{ "category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{ "category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
}
}
));
my @fiction = evaluate_jsonpath( $obj, q{$..book[?(@.category == "fiction")]});
# @fiction = (
# { category => "fiction",
# author => "Evelyn Waugh",
# title => "Sword of Honour",
# price => 12.99
# },
# { category => "fiction",
# author => "Herman Melville",
# title => "Moby Dick",
# isbn => "0-553-21311-3",
# price => 8.99
# },
# { category => "fiction",
# author => "J. R. R. Tolkien",
# title => "The Lord of the Rings",
# isbn => "0-395-19395-8",
# price => 22.99
# }
# );
METHODS
new
Constructor for the object-oriented interface to this module. Arguments may be specified
in a hash or a hashref.
Args:
root
Required. JSONPath expressions will be evaluated with respect to this. Must be a
hashref or an arrayref.
expression
JSONPath expression to evaluate
want_ref
Set this to true if you want a reference to the thing the JSONPath expression matches,
rather than the value of said thing. Useful if you want to use this to modify hashrefs
/ arrayrefs in place.
script_engine
Defaults to "PseudoJS", which is my clever name for a subset of Javascript-like
operators for Boolean expressions. See "Filtering with PseudoJS". You may also
specify "perl" here, in which case the filter will be treated as Perl code. See
"Filtering with Perl".
evaluate_jsonpath
Evaluate a JSONPath expression on the given object. CLASS METHOD.
Args:
$json_object
JSON object for which the expression will be evaluated. If this is a scalar, it will
be treated as a JSON string and parsed into the appropriate Perl data structure first.
$expression
JSONPath expression to evaluate on the object.
%args
Misc. arguments to this method. Currently the only supported argument is 'want_ref' -
set this to true in order to return a reference to the matched portion of the object,
rather than the value of that matched portion.
evaluate
Evaluate a JSONPath expression on the object passed to the constructor. OBJECT METHOD.
Args:
$expression
JSONPath expression to evaluate on the object.
%args
Misc. arguments to this method.
Supported keys:
want_ref
Set this to true in order to return a reference to the matched portion of the
object, rather than the value of the matched portion.
want_path
Set this to true in order to return the canonical path(s) to the elements matching
the expression.
JSONPath
This code implements the JSONPath specification at JSONPath specification
<http://goessner.net/articles/JsonPath/>.
JSONPath is a tool, similar to XPath for XML, that allows one to construct queries to pick
out parts of a JSON structure.
JSONPath Expressions
From the spec: "JSONPath expressions always refer to a JSON structure in the same way as
XPath expression are used in combination with an XML document. Since a JSON structure is
usually anonymous and doesn't necessarily have a "root member object" JSONPath assumes the
abstract name $ assigned to the outer level object."
Note that in JSONPath square brackets operate on the object or array addressed by the
previous path fragment. Indices always start by 0.
Operators
$ the root object/element
@ the current object/element
. or []
child operator
.. recursive descent. JSONPath borrows this syntax from E4X.
'*' (literal asterisk)
wildcard. All objects/elements regardless their names.
[] subscript operator. XPath uses it to iterate over element collections and for
predicates. In Javascript and JSON it is the native array operator.
[,] Union operator in XPath results in a combination of node sets. JSONPath allows
alternate names or array indices as a set.
[start:end:step]
array slice operator borrowed from ES4.
?() applies a filter (script) expression. See Filtering.
() script expression, using the underlying script engine. Handled the same as "?()".
Filtering
Filters are the most powerful feature of JSONPath. They allow the caller to retrieve data
conditionally, similar to Perl's "grep" operator.
Filters are specified using the '?(' token, terminated by ')'. Anything in between these
two tokens is treated as a filter expression. Filter expressions must return a boolean
value.
Filtering with PseudoJS
By default, this module uses a limited subset of Javascript expressions to evaluate
filters. Using this script engine, specify the filter in the form "<LHS> <operator>
<RHS>", or "<LHS>". This latter case will be evaluated as "<LHS> is true".
<LHS> must be a valid JSONPath expression. <RHS> must be a scalar value; comparison of two
JSONPath expressions is not supported at this time.
Example:
Using the JSON in SYNOPSIS above and the JSONPath expression "$..book[?(@.category ==
"fiction")]", the filter expression "@.category == "fiction"" will match all values having
a value of "fiction" for the key "category".
Filtering with Perl
When the script engine is set to "perl", filter Using the JSON in SYNOPSIS above and the
JSONPath expression "$..book[?(@.category == "fiction")]",
This is understandably dangerous. Although steps have been taken (Perl expressions are
evaluated using Safe and a limited set of permitted opcodes) to reduce the risk, callers
should be aware of the risk when using filters.
When filtering in Perl, there are some differences between the JSONPath spec and this
implementation.
* JSONPath uses the token '$' to refer to the root node. As this is not valid Perl, this
should be
replaced with '$root' in a filter expression.
* JSONPath uses the token '@' to refer to the current node. This is also not valid Perl.
Use '$_'
instead.
AUTHOR
Kit Peters <popefelix@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2021 by Kit Peters.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.