Toby Inkster > JSON-Path-0.205 > JSON::Path

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Module Version: 0.205   Source  

NAME ^

JSON::Path - search nested hashref/arrayref structures using JSONPath

SYNOPSIS ^

 my $data = {
  "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,
      },
    ],
  },
 };
 
 # All books in the store
 my $jpath   = JSON::Path->new('$.store.book[*]');
 my @books   = $jpath->values($data);
 
 # The author of the last (by order) book
 my $jpath   = JSON::Path->new('$..book[-1:].author');
 my $tolkien = $jpath->value($data);
 
 # Convert all authors to uppercase
 use JSON::Path 'jpath_map';
 jpath_map { uc $_ } $object, '$.store.book[*].author';

DESCRIPTION ^

This module implements JSONPath, an XPath-like language for searching JSON-like structures.

JSONPath is described at http://goessner.net/articles/JsonPath/.

Constructor

JSON::Path->new($string)

Given a JSONPath expression $string, returns a JSON::Path object.

Methods

values($object)

Evaluates the JSONPath expression against an object. The object $object can be either a nested Perl hashref/arrayref structure, or a JSON string capable of being decoded by JSON::from_json.

Returns a list of structures from within $object which match against the JSONPath expression. In scalar context, returns the number of matches.

value($object)

Like values, but returns just the first value. This method is an lvalue sub, which means you can assign to it:

  my $person = { name => "Robert" };
  my $path = JSON::Path->new('$.name');
  $path->value($person) = "Bob";
paths($object)

As per values but instead of returning structures which match the expression, returns canonical JSONPaths that point towards those structures.

get($object)

In list context, identical to values, but in scalar context returns the first result.

set($object, $value, $limit)

Alters $object, setting the paths to $value. If set, then $limit limits the number of changes made.

Returns the number of changes made.

map($object, $coderef)

Conceptually similar to Perl's map keyword. Executes the coderef (in scalar context!) for each match of the path within the object, and sets a new value from the coderef's return value. Within the coderef, $_ may be used to access the old value, and $. may be used to access the curent canonical JSONPath.

to_string

Returns the original JSONPath expression as a string.

This method is usually not needed, as the JSON::Path should automatically stringify itself as appropriate. i.e. the following works:

 my $jpath = JSON::Path->new('$.store.book[*].author');
 print "I'm looking for: " . $jpath . "\n";

Functions

The following functions are available for export, but are not exported by default:

jpath($object, $path_string)

Shortcut for JSON::Path->new($path_string)->values($object).

jpath1($object, $path_string)

Shortcut for JSON::Path->new($path_string)->value($object). Like value, it can be used as an lvalue.

jpath_map { CODE } $object, $path_string

Shortcut for JSON::Path->new($path_string)->map($object, $code).

PERL SPECIFICS ^

JSONPath is intended as a cross-programming-language method of searching nested object structures. There are however, some things you need to think about when using JSONPath in Perl...

JSONPath Embedded Perl Expressions

JSONPath expressions may contain subexpressions that are evaluated using the native host language. e.g.

 $..book[?($_->{author} =~ /tolkien/i)]

The stuff between "?(" and ")" is a Perl expression that must return a boolean, used to filter results. As arbitrary Perl may be used, this is clearly quite dangerous unless used in a controlled environment. Thus, it's disabled by default. To enable, set:

 $JSON::Path::Safe = 0;

There are some differences between the JSONPath spec and this implementation.

Blessed Objects

Blessed objects are generally treated as atomic values; JSON::Path will not follow paths inside them. The exception to this rule are blessed objects where:

  Scalar::Util::blessed($object)
  && $object->can('typeof')
  && $object->typeof =~ /^(ARRAY|HASH)$/

which are treated as an unblessed arrayref or hashref appropriately.

BUGS ^

Please report any bugs to http://rt.cpan.org/.

SEE ALSO ^

Specification: http://goessner.net/articles/JsonPath/.

Implementations in PHP, Javascript and C#: http://code.google.com/p/jsonpath/.

Related modules: JSON, JSON::JOM, JSON::T, JSON::GRDDL, JSON::Hyper, JSON::Schema.

Similar functionality: Data::Path, Data::DPath, Data::SPath, Hash::Path, Path::Resolver::Resolver::Hash, Data::Nested, Data::Hierarchy... yes, the idea's not especially new. What's different is that JSON::Path uses a vaguely standardised syntax with implementations in at least three other programming languages.

AUTHOR ^

Toby Inkster <tobyink@cpan.org>.

This module is pretty much a straight line-by-line port of the PHP JSONPath implementation (version 0.8.x) by Stefan Goessner. See http://code.google.com/p/jsonpath/.

COPYRIGHT AND LICENCE ^

Copyright 2007 Stefan Goessner.

Copyright 2010-2013 Toby Inkster.

This module is tri-licensed. It is available under the X11 (a.k.a. MIT) licence; you can also redistribute it and/or modify it under the same terms as Perl itself.

a.k.a. "The MIT Licence"

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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