Travis Build

JsonPath - Origin

This gem was forked, than re-written from this Gem: JsonPath. Since the original owner clearly abandoned that project, I took the liberty to fork it, and start fixing it. Please feel free to submit any issues you may encounter. PRs are very welcomed.

JsonPath

This is an implementation of http://goessner.net/articles/JsonPath/.

What is JsonPath?

JsonPath is a way of addressing elements within a JSON object. Similar to xpath of yore, JsonPath lets you traverse a json object and manipulate or access it.

Usage

Command-line

There is stand-alone usage through the binary jsonpathv2

jsonpathv2 [expression] (file|string)

If you omit the second argument, it will read stdin, assuming one valid JSON object
per line. Expression must be a valid jsonpathv2 expression.

Library

To use JsonPath as a library simply include and get goin'!

require 'jsonpathv2'

json = <<-HERE_DOC
{"store":
  {"bicycle":
    {"price":19.95, "color":"red"},
    "book":[
      {"price":8.95, "category":"reference", "title":"Sayings of the Century", "author":"Nigel Rees"},
      {"price":12.99, "category":"fiction", "title":"Sword of Honour", "author":"Evelyn Waugh"},
      {"price":8.99, "category":"fiction", "isbn":"0-553-21311-3", "title":"Moby Dick", "author":"Herman Melville","color":"blue"},
      {"price":22.99, "category":"fiction", "isbn":"0-395-19395-8", "title":"The Lord of the Rings", "author":"Tolkien"}
    ]
  }
}
HERE_DOC

Now that we have a JSON object, let's get all the prices present in the object. We create an object for the path in the following way.

path = JsonPath.new('$..price')

Now that we have a path, let's apply it to the object above.

path.on(json)
# => [19.95, 8.95, 12.99, 8.99, 22.99]

Or on some other object ...

path.on('{"books":[{"title":"A Tale of Two Somethings","price":18.88}]}')
# => [18.88]

You can also just combine this into one mega-call with the convenient JsonPath.on method.

JsonPath.on(json, '$..author')
# => ["Nigel Rees", "Evelyn Waugh", "Herman Melville", "Tolkien"]

Of course the full JsonPath syntax is supported, such as array slices

JsonPath.new('$..book[::2]').on(json)
# => [
#      {"price"=>8.95, "category"=>"reference", "author"=>"Nigel Rees", "title"=>"Sayings of the Century"},
#      {"price"=>8.99, "category"=>"fiction", "author"=>"Herman Melville", "title"=>"Moby Dick", "isbn"=>"0-553-21311-3"}
#    ]

...and evals.

JsonPath.new('$..price[?(@ < 10)]').on(json)
# => [8.95, 8.99]

There is a convenience method, #first that gives you the first element for a JSON object and path.

JsonPath.new('$..color').first(object)
# => "red"

As well, we can directly create an Enumerable at any time using #[].

enum = JsonPath.new('$..color')[object]
# => #<JsonPath::Enumerable:...>
enum.first
# => "red"
enum.any?{ |c| c == 'red' }
# => true

You can optionally prevent eval from being called on sub-expressions by passing in :allow_eval => false to the constructor.

Manipulation

If you'd like to do substitution in a json object, you can use #gsub or #gsub! to modify the object in place.

JsonPath.for('{"candy":"lollipop"}').gsub('$..candy') {|v| "big turks" }.to_hash

The result will be

{'candy' => 'big turks'}

If you'd like to remove all nil keys, you can use #compact and #compact!. To remove all keys under a certain path, use #delete or #delete!. You can even chain these methods together as follows:

json = '{"candy":"lollipop","noncandy":null,"other":"things"}'
o = JsonPath.for(json).
  gsub('$..candy') {|v| "big turks" }.
  compact.
  delete('$..other').
  to_hash
# => {"candy" => "big turks"}