A fast JSON parser and Object marshaller as a Ruby gem.
gem install oj
or in Bundler:
gem 'oj'
Documentation: http://www.ohler.com/oj, http://rubydoc.info/gems/oj
GitHub repo: https://github.com/ohler55/oj
RubyGems repo: https://rubygems.org/gems/oj
Follow @peterohler on Twitter for announcements and news about the Oj gem.
- Oj::ParseError is now thrown instead of SyntaxError when there are multiple JSON documents in a string or file and there is no proc or block associated with the parse call.
- An exception is now raised if there are multiple JSON documents in a string or file if there is no proc or block associated with the parse call.
Optimized JSON (Oj), as the name implies, was written to provide speed optimized JSON handling. It was designed as a faster alternative to Yajl and other common Ruby JSON parsers. So far it has achieved that, and is about 2 times faster than any other Ruby JSON parser, and 3 or more times faster at serializing JSON.
Oj has several dump or serialization modes which control how Ruby Objects are
converted to JSON. These modes are set with the :mode option in either the
default options or as one of the options to the dump method. The default mode
is the :object mode.
-
:strictmode will only allow the 7 basic JSON types to be serialized. Any otherObjectwill raise anException. -
:nullmode replaces anyObjectthat is not one of the JSON types with a JSONnull. -
:objectmode will dump anyObjectas a JSONObjectwith keys that match the RubyObject's variable names without the '@' prefix character. This is the highest performance mode. -
:compatmode attempts to be compatible with other systems. It will serialize anyObject, but will check to see if theObjectimplements anto_hashorto_jsonmethod. If either exists, that method is used for serializing theObject. Sinceas_jsonis more flexible and produces more consistent output, it is preferred over theto_jsonmethod. If neither theto_jsonorto_hashmethods exists, then the Oj internalObjectvariable encoding is used.
To change default serialization mode:
Oj.default_options = {:mode => :compat }Oj is compatible with Ruby 1.8.7, 1.9.2, 1.9.3, 2.0.0, 2.1, 2.2 and RBX. Support for JRuby has been removed as JRuby no longer supports C extensions and there are bugs in the older versions that are not being fixed.
Although up until 4.1 Rails uses multi_json, an issue in Rails causes ActiveSupport to fail to make use Oj for JSON handling.
There is a
gem to patch this for
Rails 3.2 and 4.0. As of the Oj 2.6.0 release the default behavior is to not use
the to_json() method unless the :use_to_json option is set. This provides
another work around to the rails older and newer behavior.
The latest ActiveRecord is able to work with Oj by simply using the line:
serialize :my_attr, Oj
In version Rails 4.1, multi_json has been removed, and this patch is unnecessary and will no longer work.
Instead, use the oj_mimic_json gem along with oj in your Gemfile to have Oj mimic the JSON gem and be used in its place by ActiveSupport JSON handling:
gem 'oj'
gem 'oj_mimic_json'
Two settings in Oj are useful for parsing but do expose a vulnerability if used from an untrusted source. Symbolized
keys can cause memory to be filled with previous versions of ruby. Ruby 2.1 and below does not garbage collect Symbols. The same is true for auto
defining classes in all versions of ruby; memory will also be exhausted if too many classes are automatically defined. Auto defining is a useful
feature during development and from trusted sources but it allows too many classes to be created in the object load
mode and auto defined is used with an untrusted source. The Oj.strict_load() method sets and uses the most strict and safest options. It should be used by developers who find it difficult to understand the options available in Oj.
The options in Oj are designed to provide flexibility to the developer. This flexibility allows Objects to be serialized
and deserialized. No methods are ever called on these created Objects but that does not stop the developer from calling
methods on them. As in any system, check your inputs before working with them. Taking an arbitrary String
from a user and evaluating it is never a good idea from an unsecure source. The same is true for Object attributes as
they are not more than Strings. Always check inputs from untrusted sources.
require 'oj'
h = { 'one' => 1, 'array' => [ true, false ] }
json = Oj.dump(h)
# json =
# {
# "one":1,
# "array":[
# true,
# false
# ]
# }
h2 = Oj.load(json)
puts "Same? #{h == h2}"
# trueOj offers a few alternative APIs for processing JSON. The fastest one is the Oj::Doc API. The Oj::Doc API takes a
completely different approach by opening a JSON document and providing calls to navigate around the JSON while it is
open. With this approach, JSON access can be well over 20 times faster than conventional JSON parsing.
The Oj::Saj and Oj::ScHandler APIs are callback parsers that
walk the JSON document depth first and makes callbacks for each element.
Both callback parser are useful when only portions of the JSON are of
interest. Performance up to 20 times faster than conventional JSON is
possible. The API is simple to use but does require a different approach than
the conventional parse followed by access approach used by conventional JSON
parsing.
Oj Strict Mode Performance compares Oj strict mode parser performance to other JSON parsers.
Oj Compat Mode Performance compares Oj compat mode parser performance to other JSON parsers.
Oj Object Mode Performance compares Oj object mode parser performance to other marshallers.
Oj Callback Performance compares Oj callback parser performance to other JSON parsers.
Fast XML parser and marshaller on RubyGems: https://rubygems.org/gems/ox
Fast XML parser and marshaller on GitHub: https://github.com/ohler55/ox
Oj Object Encoding Format describes the OJ Object JSON encoding format.
Need for Speed for an overview of how Oj::Doc was designed.
OjC, a C JSON parser: https://www.ohler.com/ojc also at https://github.com/ohler55/ojc