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.
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
To use JSON you can
require 'json'
Now you can parse a JSON document into a ruby data structure by calling
JSON.parse(document)
If you want to generate a JSON document from a ruby data structure call
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).
JSON documents can only support Hashes, Arrays, Strings, Integers and Floats.
By default if you attempt to serialize something else, JSON.generate
will
search for a #to_json
method on that object:
Position = Struct.new(:latitude, :longitude) do
def to_json(state = nil, *)
JSON::State.from_state(state).generate({
latitude: latitude,
longitude: longitude,
})
end
end
JSON.generate([
Position.new(12323.234, 435345.233),
Position.new(23434.676, 159435.324),
]) # => [{"latitude":12323.234,"longitude":435345.233},{"latitude":23434.676,"longitude":159435.324}]
If a #to_json
method isn't defined on the object, JSON.generate
will fallback to call #to_s
:
JSON.generate(Object.new) # => "#<Object:0x000000011e768b98>"
Both of these behavior can be disabled using the strict: true
option:
JSON.generate(Object.new, strict: true) # => Object not allowed in JSON (JSON::GeneratorError)
JSON.generate(Position.new(1, 2)) # => Position not allowed in JSON (JSON::GeneratorError)
Since #to_json
methods are global, it can sometimes be problematic if you need a given type to be
serialized in different ways in different locations.
Instead it is recommended to use the newer JSON::Coder
API:
module MyApp
API_JSON_CODER = JSON::Coder.new do |object|
case object
when Time
object.iso8601(3)
else
object
end
end
end
puts MyApp::API_JSON_CODER.dump(Time.now.utc) # => "2025-01-21T08:41:44.286Z"
The provided block is called for all objects that don't have a native JSON equivalent, and must return a Ruby object that has a native JSON equivalent.
To combine JSON fragments into a bigger JSON document, you can use JSON::Fragment
:
posts_json = cache.fetch_multi(post_ids) do |post_id|
JSON.generate(Post.find(post_id))
end
posts_json.map { |post_json| JSON::Fragment.new(post_json) }
JSON.generate({ posts: posts_json, count: posts_json.count })
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 remote code execution vulnerabilities.
To create a JSON document from a ruby data structure, you can call
JSON.generate
like that:
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:
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):
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:
class Range
def self.json_create(o)
new(*o['data'])
end
end
Now it possible to serialise/deserialise ranges as well:
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:
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.
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
Florian Frank mailto:flori@ping.de
Ruby License, see https://www.ruby-lang.org/en/about/license.txt.
The latest version of this library can be downloaded at
Online Documentation should be located at