# JSON implementation for Ruby [![CI](https://github.com/ruby/json/actions/workflows/ci.yml/badge.svg)](https://github.com/ruby/json/actions/workflows/ci.yml) ## Description This is an implementation of the JSON specification according to RFC 7159 http://www.ietf.org/rfc/rfc7159.txt . The JSON generator generate UTF-8 character sequences by default. If an :ascii\_only option with a true value is given, they escape all non-ASCII and control characters with \uXXXX escape sequences, and support UTF-16 surrogate pairs in order to be able to generate the whole range of unicode code points. All strings, that are to be encoded as JSON strings, should be UTF-8 byte sequences on the Ruby side. To encode raw binary strings, that aren't UTF-8 encoded, please use the to\_json\_raw\_object method of String (which produces an object, that contains a byte array) and decode the result on the receiving endpoint. ## Installation It's recommended to use the extension variant of JSON, because it's faster than the pure ruby variant. If you cannot build it on your system, you can settle for the latter. Install the gem and add to the application's Gemfile by executing: $ bundle add json If bundler is not being used to manage dependencies, install the gem by executing: $ gem install json There is also a pure ruby json only variant of the gem, that can be installed with: $ gem install json_pure ## Usage To use JSON you can ```ruby require 'json' ``` to load the installed variant (either the extension `'json'` or the pure variant `'json_pure'`). If you have installed the extension variant, you can pick either the extension variant or the pure variant by typing ```ruby require 'json/ext' ``` or ```ruby require 'json/pure' ``` Now you can parse a JSON document into a ruby data structure by calling ```ruby JSON.parse(document) ``` If you want to generate a JSON document from a ruby data structure call ```ruby JSON.generate(data) ``` You can also use the `pretty_generate` method (which formats the output more verbosely and nicely) or `fast_generate` (which doesn't do any of the security checks generate performs, e. g. nesting deepness checks). ## Handling arbitrary types > [!CAUTION] > You should never use `JSON.unsafe_load` nor `JSON.parse(str, create_additions: true)` to parse untrusted user input, > as it can lead to remove code execution vulnerabilities. To create a JSON document from a ruby data structure, you can call `JSON.generate` like that: ```ruby json = JSON.generate [1, 2, {"a"=>3.141}, false, true, nil, 4..10] # => "[1,2,{\"a\":3.141},false,true,null,\"4..10\"]" ``` To get back a ruby data structure from a JSON document, you have to call JSON.parse on it: ```ruby JSON.parse json # => [1, 2, {"a"=>3.141}, false, true, nil, "4..10"] ``` Note, that the range from the original data structure is a simple string now. The reason for this is, that JSON doesn't support ranges or arbitrary classes. In this case the json library falls back to call `Object#to_json`, which is the same as `#to_s.to_json`. It's possible to add JSON support serialization to arbitrary classes by simply implementing a more specialized version of the `#to_json method`, that should return a JSON object (a hash converted to JSON with `#to_json`) like this (don't forget the `*a` for all the arguments): ```ruby class Range def to_json(*a) { 'json_class' => self.class.name, # = 'Range' 'data' => [ first, last, exclude_end? ] }.to_json(*a) end end ``` The hash key `json_class` is the class, that will be asked to deserialise the JSON representation later. In this case it's `Range`, but any namespace of the form `A::B` or `::A::B` will do. All other keys are arbitrary and can be used to store the necessary data to configure the object to be deserialised. If the key `json_class` is found in a JSON object, the JSON parser checks if the given class responds to the `json_create` class method. If so, it is called with the JSON object converted to a Ruby hash. So a range can be deserialised by implementing `Range.json_create` like this: ```ruby class Range def self.json_create(o) new(*o['data']) end end ``` Now it possible to serialise/deserialise ranges as well: ```ruby json = JSON.generate [1, 2, {"a"=>3.141}, false, true, nil, 4..10] # => "[1,2,{\"a\":3.141},false,true,null,{\"json_class\":\"Range\",\"data\":[4,10,false]}]" JSON.parse json # => [1, 2, {"a"=>3.141}, false, true, nil, 4..10] json = JSON.generate [1, 2, {"a"=>3.141}, false, true, nil, 4..10] # => "[1,2,{\"a\":3.141},false,true,null,{\"json_class\":\"Range\",\"data\":[4,10,false]}]" JSON.unsafe_load json # => [1, 2, {"a"=>3.141}, false, true, nil, 4..10] ``` `JSON.generate` always creates the shortest possible string representation of a ruby data structure in one line. This is good for data storage or network protocols, but not so good for humans to read. Fortunately there's also `JSON.pretty_generate` (or `JSON.pretty_generate`) that creates a more readable output: ```ruby puts JSON.pretty_generate([1, 2, {"a"=>3.141}, false, true, nil, 4..10]) [ 1, 2, { "a": 3.141 }, false, true, null, { "json_class": "Range", "data": [ 4, 10, false ] } ] ``` There are also the methods `Kernel#j` for generate, and `Kernel#jj` for `pretty_generate` output to the console, that work analogous to Core Ruby's `p` and the `pp` library's `pp` methods. ## Development ### Release Update the `lib/json/version.rb` file. ``` rbenv shell 2.6.5 rake build gem push pkg/json-2.3.0.gem rbenv shell jruby-9.2.9.0 rake build gem push pkg/json-2.3.0-java.gem ``` ## Author Florian Frank ## License Ruby License, see https://www.ruby-lang.org/en/about/license.txt. ## Download The latest version of this library can be downloaded at * https://rubygems.org/gems/json Online Documentation should be located at * https://www.rubydoc.info/gems/json [Ragel]: http://www.colm.net/open-source/ragel/