Code Quality Rank: L1
Programming language: C++
License: GNU Lesser General Public License v3.0 only
Tags: JSON    

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QJson Build Status

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It can represents integer, real number, string, an ordered sequence of value, and a collection of name/value pairs.

QJson is a qt-based library that maps JSON data to QVariant objects. JSON arrays will be mapped to QVariantList instances, while JSON's objects will be mapped to QVariantMap.


QJson requires:

  • Qt 4.5 or greater
  • cmake 2.6 or greater

Some possible cmake options:

  • -DCMAKE_BUILD_TYPE=DEBUG: enables some debug output (other than making easier to debug the code)
  • -DQJSON_BUILD_TESTS=yes or -DKDE4_BUILD_TESTS=yes: builds the unit tests
  • -DCMAKE_INSTALL_PREFIX=${HOME}/testinstall: install qjson in a custom directory
  • -DCMAKE_INCLUDE_PATH=${HOME}/testinstall/include: include a custom include directory
  • -DCMAKE_LIBRARY_PATH=${HOME}/testinstall/lib: include a custom library directory
  • -DLIB_DESTINATION=lib64: if you have a 64 bit system with separate libraries for 64 bit libraries
  • -DQJSON_VERBOSE_DEBUG_OUTPUT:BOOL=ON: more debugging statements are generated by the parser. It's useful only if you are trying to fix the bison grammar.

For Unix/Linux/Mac:

mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=_preferred_path_ ..
make install
/sbin/ldconfig #if necessary


The recommended way to submit your changes is via a pull request.

Before submitting a patch please ensure:

  • Patched code compiles.
  • The patch is fixing a specific issue or implementing a new feature (it’s not doing multiple things at the same time).
  • QJson unit tests have been updated.
  • QJson unit tests are passing.

Unit testing

QJson unit tests are located under the tests directory. You can enable them passing the -DQJSON_BUILD_TESTS=yes option to cmake.

Note well: make sure you followed the build instructions.

To run all the unit tests move into the build directory and type:

make tests

If you want to run the QJson::Parser unit tests just type:


If you want to run the QJson::Serializer unit tests just type:


If you want to run the QJson::QObjectHelper tests just type:


If you want to test the QJson parser against a specific JSON object you can use the cmdline_tester program.

This binary is located under the tests directory and has a straightforward syntax:

./tests/cmdline_tester/cmdline_tester text_file_containing_json_object

The command will convert the JSON object to a QVariant and dump it to stdout. More options are available via cli options, just checkout the --help output.

Note well: cmdline_tester relies on qDebug() to dump the object. qDebug has some limitations, like being unable to print utf8 chars.


This library is licensed under the Lesser GNU General Public License version 2.1. See the COPYING.lib file for more information.


*Note that all licence references and agreements mentioned in the QJson README section above are relevant to that project's source code only.