...by setting the archive directory variable
8.0 KiB
Introduction
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.
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.
Using JsonCpp in your project
The recommended approach to integrating JsonCpp in your project is to build
the amalgamated source (a single .cpp
file) with your own build system. This
ensures consistency of compilation flags and ABI compatibility. See the section
"Generating amalgamated source and header" for instructions.
The include/
should be added to your compiler include path. Jsoncpp headers
should be included as follow:
#include <json/json.h>
If JsonCpp was built as a dynamic library on Windows, then your project needs to
define the macro JSON_DLL
.
Building and testing with CMake
CMake is a C++ Makefiles/Solution generator. It is usually available on most Linux system as package. On Ubuntu:
sudo apt-get install cmake
Note that Python is also required to run the JSON reader/writer tests. If missing, the build will skip running those tests.
When running CMake, a few parameters are required:
- a build directory where the makefiles/solution are generated. It is also used to store objects, libraries and executables files.
- the generator to use: makefiles or Visual Studio solution? What version or Visual Studio, 32 or 64 bits solution?
Steps for generating solution/makefiles using cmake-gui
:
- Make "source code" point to the source directory.
- Make "where to build the binary" point to the directory to use for the build.
- Click on the "Grouped" check box.
- Review JsonCpp build options (tick
BUILD_SHARED_LIBS
to build as a dynamic library). - Click the configure button at the bottom, then the generate button.
- The generated solution/makefiles can be found in the binary directory.
Alternatively, from the command-line on Unix in the source directory:
mkdir -p build/debug
cd build/debug
cmake -DCMAKE_BUILD_TYPE=debug -DBUILD_STATIC_LIBS=ON -DBUILD_SHARED_LIBS=OFF -DARCHIVE_INSTALL_DIR=. -G "Unix Makefiles" ../..
make
Running cmake -
" will display the list of available generators (passed using
the -G
option).
By default CMake hides compilation commands. This can be modified by specifying
-DCMAKE_VERBOSE_MAKEFILE=true
when generating makefiles.
Building and testing with SCons
Note: The SCons-based build system is deprecated. Please use CMake; see the section above.
JsonCpp can use Scons as a build system. Note that SCons requires Python to be installed.
Invoke SCons as follows:
scons platform=$PLATFORM [TARGET]
where $PLATFORM
may be one of:
suncc
: Sun C++ (Solaris)vacpp
: Visual Age C++ (AIX)mingw
msvc6
: Microsoft Visual Studio 6 service pack 5-6msvc70
: Microsoft Visual Studio 2002msvc71
: Microsoft Visual Studio 2003msvc80
: Microsoft Visual Studio 2005msvc90
: Microsoft Visual Studio 2008linux-gcc
: Gnu C++ (linux, also reported to work for Mac OS X)
If you are building with Microsoft Visual Studio 2008, you need to set up the
environment by running vcvars32.bat
(e.g. MSVC 2008 command prompt) before
running SCons.
Running the tests manually
You need to run tests manually only if you are troubleshooting an issue.
In the instructions below, replace path/to/jsontest
with the path of the
jsontest
executable that was compiled on your platform.
cd test
# This will run the Reader/Writer tests
python runjsontests.py path/to/jsontest
# This will run the Reader/Writer tests, using JSONChecker test suite
# (http://www.json.org/JSON_checker/).
# Notes: not all tests pass: JsonCpp is too lenient (for example,
# it allows an integer to start with '0'). The goal is to improve
# strict mode parsing to get all tests to pass.
python runjsontests.py --with-json-checker path/to/jsontest
# This will run the unit tests (mostly Value)
python rununittests.py path/to/test_lib_json
# You can run the tests using valgrind:
python rununittests.py --valgrind path/to/test_lib_json
Running the tests using scons
Note that tests can be run using SCons using the check
target:
scons platform=$PLATFORM check
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.
Generating amalgamated source and header
JsonCpp is provided with a script to generate a single header and a single source file to ease inclusion into an existing project. The amalgamated source can be generated at any time by running the following command from the top-directory (this requires Python 2.6):
python amalgamate.py
It is possible to specify header name. See the -h
option for detail.
By default, the following files are generated:
dist/jsoncpp.cpp
: source file that needs to be added to your project.dist/json/json.h
: corresponding header file for use in your project. It is equivalent to includingjson/json.h
in non-amalgamated source. This header only depends on standard headers.dist/json/json-forwards.h
: header that provides forward declaration of all JsonCpp types.
The amalgamated sources are generated by concatenating JsonCpp source in the
correct order and defining the macro JSON_IS_AMALGAMATION
to prevent inclusion
of other headers.
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 indexN
.
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 byjsontest
from readingtest_complex_01.json
.test_complex_01.rewrite
: JSON document written byjsontest
using theJson::Value
parsed fromtest_complex_01.json
and serialized usingJson::StyledWritter
.test_complex_01.actual-rewrite
: flattened JSON element tree produced byjsontest
from readingtest_complex_01.rewrite
.test_complex_01.process-output
:jsontest
output, typically useful for understanding parsing errors.
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.