JsonCpp

JSON is a lightweight data-interchange format. It can represent numbers, strings, ordered sequences of values, and collections of name/value pairs.

JsonCpp is a C++ library that allows manipulating JSON values, including serialization and deserialization to and from strings. It can also preserve existing comment in unserialization/serialization steps, making it a convenient format to store user input files.

Documentation

JsonCpp documentation is generated using Doxygen.

A note on backward-compatibility

• 1.y.z is built with C++11.
• 0.y.z can be used with older compilers.
• Major versions maintain binary-compatibility.

Contributing to JsonCpp

Building and testing with Meson/Ninja

Thanks to David Seifert (@SoapGentoo), we (the maintainers) now use meson and ninja to build for debugging, as well as for continuous integration (see ./travis_scripts/meson_builder.sh ). Other systems may work, but minor things like version strings might break.

First, install both meson (which requires Python3) and ninja. If you wish to install to a directory other than /usr/local, set an environment variable called DESTDIR with the desired path: DESTDIR=/path/to/install/dir

Then,

cd jsoncpp/
BUILD_TYPE=debug
#BUILD_TYPE=release
LIB_TYPE=shared
#LIB_TYPE=static
meson --buildtype ${BUILD_TYPE} --default-library ${LIB_TYPE} . build-${LIB_TYPE}
#ninja -v -C build-${LIB_TYPE} test # This stopped working on my Mac.
ninja -v -C build-${LIB_TYPE}
cd build-${LIB_TYPE}
meson test --no-rebuild --print-errorlogs
sudo ninja install

Building and testing with other build systems

See https://github.com/open-source-parsers/jsoncpp/wiki/Building

Running the tests manually

You need to run tests manually only if you are troubleshooting an issue.

In the instructions below, replace path/to/jsontest with the path of the jsontest executable that was compiled on your platform.

cd test
# This will run the Reader/Writer tests
python runjsontests.py path/to/jsontest

# This will run the Reader/Writer tests, using JSONChecker test suite
# (http://www.json.org/JSON_checker/).
# Notes: not all tests pass: JsonCpp is too lenient (for example,
# it allows an integer to start with '0'). The goal is to improve
# strict mode parsing to get all tests to pass.
python runjsontests.py --with-json-checker path/to/jsontest

# This will run the unit tests (mostly Value)
python rununittests.py path/to/test_lib_json

# You can run the tests using valgrind:
python rununittests.py --valgrind path/to/test_lib_json

Building the documentation

Run the Python script doxybuild.py from the top directory:

python doxybuild.py --doxygen=$(which doxygen) --open --with-dot

See doxybuild.py --help for options.

Adding a reader/writer test

To add a test, you need to create two files in test/data:

• a TESTNAME.json file, that contains the input document in JSON format.
• a TESTNAME.expected file, that contains a flatened representation of the input document.

The TESTNAME.expected file format is as follows:

• Each line represents a JSON element of the element tree represented by the input document.
• Each line has two parts: the path to access the element separated from the element value by =. Array and object values are always empty (i.e. represented by either [] or {}).
• Element path . represents the root element, and is used to separate object members. [N] is used to specify the value of an array element at index N.

See the examples test_complex_01.json and test_complex_01.expected to better understand element paths.

Understanding reader/writer test output

When a test is run, output files are generated beside the input test files. Below is a short description of the content of each file:

• test_complex_01.json: input JSON document.
• test_complex_01.expected: flattened JSON element tree used to check if parsing was corrected.
• test_complex_01.actual: flattened JSON element tree produced by jsontest from reading test_complex_01.json.
• test_complex_01.rewrite: JSON document written by jsontest using the Json::Value parsed from test_complex_01.json and serialized using Json::StyledWritter.
• test_complex_01.actual-rewrite: flattened JSON element tree produced by jsontest from reading test_complex_01.rewrite.
• test_complex_01.process-output: jsontest output, typically useful for understanding parsing errors.

Using JsonCpp in your project

Amalgamated source

https://github.com/open-source-parsers/jsoncpp/wiki/Amalgamated

The Meson Build System

If you are using the Meson Build System, then you can get a wrap file by downloading it from Meson WrapDB, or simply use meson wrap install jsoncpp.

Other ways

If you have trouble, see the Wiki, or post a question as an Issue.

License

See the LICENSE file for details. In summary, JsonCpp is licensed under the MIT license, or public domain if desired and recognized in your jurisdiction.