JsonCpp - JSON data format manipulation library

JsonCpp Documentation

0.6.0-rc2

Introduction

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

Here is an example of JSON data:

// Configuration options

{

    // Default encoding for text

    "encoding" : "UTF-8",

    // Plug-ins loaded at start-up

    "plug-ins" : [

        "python",

        "c++",

        "ruby"

        ],

    // Tab indent size

    "indent" : { "length" : 3, "use_space": true }

}

Features

• read and write JSON document
• attach C and C++ style comments to element during parsing
• rewrite JSON document preserving original comments

Notes: Comments used to be supported in JSON but where removed for portability (C like comments are not supported in Python). Since comments are useful in configuration/input file, this feature was preserved.

Code example

Json::Value root;   // will contains the root value after parsing.
Json::Reader reader;

bool parsingSuccessful = reader.parse( config_doc, root );

if ( !parsingSuccessful )

{

    // report to the user the failure and their locations in the document.

    std::cout  << "Failed to parse configuration\n"

               << reader.getFormattedErrorMessages();

    return;

}

// Get the value of the member of root named 'encoding', return 'UTF-8' if there is no

// such member.

std::string encoding = root.get("encoding", "UTF-8" ).asString();

// Get the value of the member of root named 'encoding', return a 'null' value if

// there is no such member.

const Json::Value plugins = root["plug-ins"];

for ( int index = 0; index < plugins.size(); ++index )  // Iterates over the sequence elements.

   loadPlugIn( plugins[index].asString() );

setIndentLength( root["indent"].get("length", 3).asInt() );

setIndentUseSpace( root["indent"].get("use_space", true).asBool() );

// ...

// At application shutdown to make the new configuration document:

// Since Json::Value has implicit constructor for all value types, it is not

// necessary to explicitly construct the Json::Value object:

root["encoding"] = getCurrentEncoding();

root["indent"]["length"] = getCurrentIndentLength();

root["indent"]["use_space"] = getCurrentIndentUseSpace();

Json::StyledWriter writer;

// Make a new JSON document for the configuration. Preserve original comments.

std::string outputConfig = writer.write( root );

// You can also use streams.  This will put the contents of any JSON

// stream at a particular sub-value, if you'd like.

std::cin >> root["subtree"];

// And you can write to a stream, using the StyledWriter automatically.

std::cout << root;

Build instructions

The build instructions are located in the file README.txt in the top-directory of the project.

Permanent link to the latest revision of the file in subversion: latest README.txt

Download

The sources can be downloaded from SourceForge download page.

The latest version of the source is available in the project's subversion repository: http://jsoncpp.svn.sourceforge.net/svnroot/jsoncpp/trunk/

To checkout the source, see the following instructions.

What's New?

The description of latest changes can be found in NEWS.txt in the top-directory of the project.

Permanent link to the latest revision of the file in subversion: latest NEWS.txt

Project links

• json-cpp home
• json-cpp sourceforge project

Related links

• JSON Specification and alternate language implementations.
• YAML A data format designed for human readability.
• UTF-8 and Unicode FAQ.

License

See file LICENSE in the top-directory of the project.

Basically JsonCpp is licensed under MIT license, or public domain if desired and recognized in your jurisdiction.

Author:

Baptiste Lepilleur <blep@users.sourceforge.net>