Browse by type
jsoncons is a C++, header-only library for constructing JSON and JSON-like data formats such as CBOR. For each supported data format, it enables you to work with the data in a number of ways:
As a variant-like, allocator-aware, data structure, basic_json
As a strongly typed C++ data structure that implements jsoncons reflection traits
With cursor-level access to a stream of parse events, somewhat analogous to StAX pull parsing and push serializing in the XML world.
Compared to other JSON libraries, jsoncons has been designed to handle very large JSON texts. At its heart are SAX-style parsers and serializers. It supports reading an entire JSON text in memory in a variant-like structure. But it also supports efficient access to the underlying data using StAX-style pull parsing and push serializing. And it supports incremental parsing into a user's preferred types, using information about user types provided by specializations of reflection traits.
The jsoncons data model supports the familiar JSON types - nulls, booleans, numbers, strings, arrays, objects - plus byte strings. In addition, jsoncons supports semantic tagging of datetimes, epoch times, big integers, big decimals, big floats and binary encodings. This allows it to preserve these type semantics when parsing JSON-like data formats such as CBOR that have them.
jsoncons is distributed under the Boost Software License.
jsoncons is free but welcomes support to sustain its development. If you find this library helpful, please consider making a one time donation or becoming a :heart: sponsor.
As the jsoncons library has evolved, names have sometimes changed, see deprecated. To ease transition, jsoncons deprecates the
old names but continues to support many of them. The deprecated names can be suppressed by defining the macro
JSONCONS_NO_DEPRECATED, and doing so is recommended for new code.
"Apache Kvrocks consistently utilizes jsoncons to offer support for JSON data structures to users. We find the development experience with jsoncons outstanding!"
"I have been using your library in my native language – R – and have created an R package making it easy for (a) JMESpath and JSONpath queries on JSON strings or R objects and (b) for other R developers to link to your library."
"I’m using your library for an external interface to pass data, as well as using the conversions from csv to json, which are really helpful for converting data for use in javascript"
"Verified that, for my needs in JSON and CBOR, it is working perfectly"
"the JSONPath feature of this library, it's great"
"We use JMESPath implementation quite extensively"
"We love your JSON Schema validator. We are using it in ER/Studio our data modelling tool to parse JSON Schema files so we can create entity relations models from them."
"the serialization lib of choice with its beautiful mappings and ease of use"
"really good" "awesome project" "very solid and very dependable" "my team loves it" "Your repo rocks!!!!!"
Get started with HealthImaging image sets and image frames using an AWS SDK
RubyGems.org rjsoncons CoppeliaSim reflect-cpp
The benchmark code is available here.
JSONPath Comparison shows how jsoncons JsonPath compares with other implementations
You can use the vcpkg platform library manager to install the jsoncons package.
Or, download the latest release and unpack the zip file. Copy the directory include/jsoncons to your include directory. If you wish to use extensions, copy include/jsoncons_ext as well.
Or, download the latest code on main.
The library requires a C++ Compiler with C++11 support. In addition the library defines jsoncons::endian,
jsoncons::basic_string_view, jsoncons::optional, and jsoncons::span, which will be typedef-ed to
their standard library equivalents if detected. Otherwise they will be typedef-ed to internal, C++11 compatible, implementations.
The library uses exceptions and in some cases std::error_code's to report errors. Apart from jsoncons::assertion_error,
all jsoncons exception classes implement the jsoncons::json_error interface.
If exceptions are disabled or if the compile time macro JSONCONS_NO_EXCEPTIONS is defined, throws become calls to std::terminate.
For the examples below you need to include some header files and initialize a string of JSON data:
#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonpath/jsonpath.hpp>
#include <iostream>
using namespace jsoncons; // for convenience
std::string data = R"(
{
"application": "hiking",
"reputons": [
{
"rater": "HikingAsylum",
"assertion": "advanced",
"rated": "Marilyn C",
"rating": 0.90,
"generated": 1514862245
}
]
}
)";
jsoncons allows you to work with the data in a number of ways:
As a variant-like data structure, basic_json
As a strongly typed C++ data structure that implements jsoncons reflection traits
With cursor-level access to a stream of parse events
int main()
{
// Parse the string of data into a json value
json j = json::parse(data);
// Does object member reputons exist?
std::cout << "(1) " << std::boolalpha << j.contains("reputons") << "\n\n";
// Get a reference to reputons array
const json& v = j["reputons"];
// Iterate over reputons array
std::cout << "(2)\n";
for (const auto& item : v.array_range())
{
// Access rated as string and rating as double
std::cout << item["rated"].as<std::string>() << ", " << item["rating"].as<double>() << "\n";
}
std::cout << "\n";
// Select all "rated" with JSONPath
std::cout << "(3)\n";
json result = jsonpath::json_query(j,"$..rated");
std::cout << pretty_print(result) << "\n\n";
// Serialize back to JSON
std::cout << "(4)\n" << pretty_print(j) << "\n\n";
}
Output:
(1) true
(2)
Marilyn C, 0.9
(3)
[
"Marilyn C"
]
(4)
{
"application": "hiking",
"reputons": [
{
"assertion": "advanced",
"generated": 1514862245,
"rated": "Marilyn C",
"rater": "HikingAsylum",
"rating": 0.9
}
]
}
jsoncons supports transforming JSON texts into C++ data structures.
The functions decode_json and encode_json
convert strings or streams of JSON data to C++ data structures and back.
Decode and encode work for all C++ classes that implement jsoncons reflection traits.
defined. jsoncons already supports many types in the standard library,
and your own types will be supported too if you specialize reflection traits
in the jsoncons namespace.
```cpp namespace ns { enum class hiking_experience {beginner,intermediate,advanced};
class hiking_reputon
{
std::string rater_;
hiking_experience assertion_;
std::string rated_;
double rating_;
std::optional<std::chrono::seconds> generated_; // assumes C++17, if not use jsoncons::optional
std::optional<std::chrono::seconds> expires_;
public:
hiking_reputon(const std::string& rater,
hiking_experience assertion,
const std::string& rated,
double rating,
const std::optional<std::chrono::seconds>& generated =
std::optional<std::chrono::seconds>(),
const std::optional<std::chrono::seconds>& expires =
std::optional<std::chrono::seconds>())
: rater_(rater), assertion_(assertion), rated_(rated), rating_(rating),
generated_(generated), expires_(expires)
{
}
const std::string& rater() const {return rater_;}
hiking_experience assertion() const {return assertion_;}
const std::string& rated() const {return rated_;}
double rating() const {return rating_;}
std::optional<std::chrono::seconds> generated() const {return generated_;}
std::optional<std::chrono::seconds> expires() const {return expires_;}
friend bool operator==(const hiking_reputon& lhs, const hiking_reputon& rhs)
{
return lhs.rater_ == rhs.rater_ && lhs.assertion_ == rhs.assertion_ &&
lhs.rated_ == rhs.rated_ && lhs.rating_ == rhs.rating_ &&
lhs.confidence_ == rhs.confidence_ && lhs.expires_ == rhs.expires_;
}
friend bool operator!=(const hiking_reputon& lhs, const hiking_reputon& rhs)
{
return !(lhs == rhs);
};
};
class hiking_reputation
{
std::string application_;
std::vector<hiking_reputon> reputons_;
public:
hiking_reputation(const std::string& application,
const std::vector<hiking_reputon>& reputons)
: application_(application),
reputons_(reputons)
{}
const std::string& application() const { return application_;}
const std::vector<hiking_reputon>& reputons() const { return reputons_;}
};
} // namespace ns
// Declare the traits. Specify which data members need to be serialized.
JSONCONS_ENUM_TRAITS(ns::hiking_experience, beginner, intermediate, advanced) // First four members listed are mandatory, generated and expires are optional JSONCONS_N_CTOR_GETTER_TRAITS(ns::hiking_reputon, 4, rater, assertion, rated, rating, generated, expires)
// All members are mandatory JSONCONS_ALL_CTOR_GETTER_TRAITS(ns::hiking_reputation, application, reputons)
int main() { // Decode the string of data into a c++ structure ns::hiking_reputation v = decode_json(data);
// Iterate over reputons array value
std::cout << "(1)\n";
for (const
$ claude mcp add jsoncons \
-- python -m otcore.mcp_server <graph>