A fast JSON parser and Object marshaller as a Ruby gem.
gem install oj
Documentation: http://www.ohler.com/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.
- Fixed bug where unterminated JSON did not raise an exception.
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 the common Ruby JSON parsers. So far is has achieved that at about 2 time faster than any other Ruby JSON parser and 3 or more times faster writing JSON.
Oj has several dump or serialization modes which control how 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.
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:strict mode will only allow the 7 basic JSON types to be serialized. Any other Object will raise and Exception.
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:null mode replaces any Object that is not one of the JSON types is replaced by a JSON null.
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:object mode will dump any Object as a JSON Object with keys that match the Ruby Object's variable names without the '@' character. This is the highest performance mode.
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:compat mode is is the compatible with other systems. It will serialize any Object but will check to see if the Object implements a to_hash() or to_json() method. If either exists that method is used for serializing the Object. The to_hash() is more flexible and produces more consistent output so it has a preference over the to_json() method. If neither the to_json() or to_hash() methods exist then the Oj internal Object variable encoding is used.
Oj is compatible with Ruby 1.8.7, 1.9.2, 1.9.3, 2.0.0, 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.
Oj is also compatible with Rails. Just make sure the Oj gem is installed and multi_json will pick it up and use it.
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.
Other parsers, the Oj::Saj and the Oj::ScHandler API 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 are 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.
Two settings in Oj are useful for parsing but do expose a vunerability if used from an untrusted source. Symbolizing keys can be used to cause memory to be filled up since Ruby does not garbage collect Symbols. The same is true for auto defining classes. Memory can be exhausted if too many classes are automatically defined. Auto defining is a useful feature during development and from trusted sources but it does allow 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 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 the Objects created. 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 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.
Copyright (c) 2012, Peter Ohler
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