Click here to Skip to main content
15,867,756 members
Articles / Web Development / HTML

JSON Spirit: A C++ JSON Parser/Generator Implemented with Boost Spirit

Rate me:
Please Sign up or sign in to vote.
4.92/5 (110 votes)
10 May 2014MIT12 min read 4.1M   24.2K   287  
A C++ JSON parser/generator written using Boost::spirit
//          Copyright John W. Wilkinson 2007 - 2011
// Distributed under the MIT License, see accompanying file LICENSE.txt

// json spirit version 4.05

// This demo shows you how to read and write JSON objects and arrays 
// using header files only, i.e. not linking to the JSON Spirit object library.
// In this demo objects are stored as a vector of name/value pairs.

#include "json_spirit_reader_template.h"
#include "json_spirit_writer_template.h"
#include <cassert>
#include <fstream>

#ifndef JSON_SPIRIT_VALUE_ENABLED
#error Please define JSON_SPIRIT_VALUE_ENABLED for the Value type to be enabled 
#endif

using namespace std;
using namespace json_spirit;

struct Address
{
    int house_number_;
    string road_;
    string town_;
    string county_;
    string country_;
};

bool operator==( const Address& a1, const Address& a2 )
{
    return ( a1.house_number_ == a2.house_number_ ) &&
           ( a1.road_         == a2.road_ ) &&
           ( a1.town_         == a2.town_ ) &&
           ( a1.county_       == a2.county_ ) &&
           ( a1.country_      == a2.country_ );
}

void write_address( Array& a, const Address& addr )
{
    Object addr_obj;

    addr_obj.push_back( Pair( "house_number", addr.house_number_ ) );
    addr_obj.push_back( Pair( "road",         addr.road_ ) );
    addr_obj.push_back( Pair( "town",         addr.town_ ) );
    addr_obj.push_back( Pair( "county",       addr.county_ ) );
    addr_obj.push_back( Pair( "country",      addr.country_ ) );

    a.push_back( addr_obj );
}

Address read_address( const Object& obj )
{
    Address addr;

    for( Object::size_type i = 0; i != obj.size(); ++i )
    {
        const Pair& pair = obj[i];

        const string& name  = pair.name_;
        const Value&  value = pair.value_;

        if( name == "house_number" )
        {
            addr.house_number_ = value.get_int();
        }
        else if( name == "road" )
        {
            addr.road_ = value.get_str();
        }
        else if( name == "town" )
        {
            addr.town_ = value.get_str();
        }
        else if( name == "county" )
        {
            addr.county_ = value.get_str();
        }
        else if( name == "country" )
        {
            addr.country_ = value.get_str();
        }
        else
        {
            assert( false );
        }
    }

    return addr;
}

void write_addrs( const char* file_name, const Address addrs[] )
{
    Array addr_array;

    for( int i = 0; i < 5; ++i )
    {
        write_address( addr_array, addrs[i] );
    }

    ofstream os( file_name );

    write_stream( Value( addr_array ), os, pretty_print );  // NB need to convert Array to a Value

    os.close();
}

vector< Address > read_addrs( const char* file_name )
{
    ifstream is( file_name );

    Value value;

    read_stream( is, value );

    const Array& addr_array = value.get_array();

    vector< Address > addrs;

    for( unsigned int i = 0; i < addr_array.size(); ++i )
    {
        addrs.push_back( read_address( addr_array[i].get_obj() ) );
    }

    return addrs;
}

int main()
{
    const Address addrs[5] = { { 42, "East Street",  "Newtown",     "Essex",         "England" },
                               { 1,  "West Street",  "Hull",        "Yorkshire",     "England" },
                               { 12, "South Road",   "Aberystwyth", "Dyfed",         "Wales"   },
                               { 45, "North Road",   "Paignton",    "Devon",         "England" },
                               { 78, "Upper Street", "Ware",        "Hertfordshire", "England" } };

    const char* file_name( "demo.txt" );

    write_addrs( file_name, addrs );

    vector< Address > new_addrs = read_addrs( file_name );

    assert( new_addrs.size() == 5 );

    for( int i = 0; i < 5; ++i )
    {
        assert( new_addrs[i] == addrs[i] );
    }

	return 0;
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The MIT License


Written By
Software Developer (Senior) Spirent Communications Plc
United Kingdom United Kingdom
This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming.

Comments and Discussions