Oj gem¶ ↑
A fast JSON parser and Object marshaller as a Ruby gem.
Installation¶ ↑
gem install oj
or in Bundler: gem 'oj'
Documentation¶ ↑
Documentation: www.ohler.com/oj, rubydoc.info/gems/oj
Source¶ ↑
GitHub repo: github.com/ohler55/oj
RubyGems repo: rubygems.org/gems/oj
Follow @peterohler on Twitter for announcements and news about the Oj gem.
Build Status¶ ↑
Release 2.12.8¶ ↑
-
mimic_JSON now supports the global/kernel JSON function that will either parse a string argument or dump an array or object argument.
Description¶ ↑
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: ruby Oj.default_options =
{:mode => :compat }
Compatibility¶ ↑
Ruby¶ ↑
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.
Rails¶ ↑
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'
Proper Use¶ ↑
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 since Ruby does not garbage collect Symbols.
The same is true for auto defining classes; 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.
Simple JSON Writing and Parsing Example¶ ↑
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}" # true
Alternative JSON Processing APIs¶ ↑
Oj 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.
Links¶ ↑
Performance Comparisons¶ ↑
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.
Links of Interest¶ ↑
Fast XML parser and marshaller on RubyGems: rubygems.org/gems/ox
Fast XML parser and marshaller on GitHub: 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: www.ohler.com/ojc also at github.com/ohler55/ojc
