rapidjsonはWriterの小さなパッケージに便利です

#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include "rapidjson/prettywriter.h"
#include 


enum class data_type {
	type_bool = 0,
	type_char = 1,
	type_uchar = 2,
	type_short = 3,
	type_ushort = 4,
	type_int = 5,
	type_uint = 6,
	type_long = 7,
	type_ulong = 8,
	type_float = 9,
	type_double = 10,
	type_string = 11,

};

class translate_writer : public rapidjson::Writer < rapidjson::StringBuffer >
{
private:
	rapidjson::StringBuffer sb;

	bool add_type_int(const char* name, data_type type, int val) {
		return this->add_array(name, [&](translate_writer* wr){
			return wr->Int((int)type) && wr->Int(val); 
		});
	}

	bool add_type_uint(const char* name, data_type type, uint32_t val) {
		return add_array(name, [&](translate_writer* wr){
			return wr->Int((int)type) && wr->Uint(val); 
		});
	}

	bool add_type_double(const char* name, data_type type, double val) {
		return add_array(name, [&](translate_writer* wr){
			return wr->Int((int)type) && wr->Double(val); 
		});
	}

public:
	translate_writer() : rapidjson::Writer<:stringbuffer>(sb) {

	}

	std::string GetString() {
		return sb.GetString();
	}

	bool add_array(const char* name, std::function func) {
		return this->Key(name) && this->StartArray() && func(this) && this->EndArray();
	}

	bool add_object(const char* name, std::function func) {
		return this->Key(name) && this->StartObject() && func(this) && this->EndObject();
	}

	bool add_char(const char* name, char val) {
		return add_type_int(name, data_type::type_char, val);
	}

	bool add_short(const char* name, short val) {
		return add_type_int(name, data_type::type_char, val);
	}

	bool add_int(const char* name, int val) {
		return add_type_int(name, data_type::type_int, val);
	}

	bool add_long(const char* name, long val) {
		return add_array(name, [&](translate_writer* wr){
			return wr->Int((int)data_type::type_long) && wr->Int64(val); 
		});
	}

	bool add_uint8(const char* name, uint8_t val) {
		return add_type_int(name, data_type::type_uchar, val);
	}

	bool add_uint16(const char* name, uint16_t val) {
		return add_type_int(name, data_type::type_uchar, val);
	}

	bool add_uint32(const char* name, uint32_t val) {
		return add_type_int(name, data_type::type_uint, val);
	}

	bool add_uint64(const char* name, uint64_t val) {
		return add_array(name, [&](translate_writer* wr) {
			return wr->Int((int)data_type::type_ulong) && wr->Uint64(val);
		});
	}

	bool add_float(const char* name, float val) {
		return add_type_double(name, data_type::type_float, val);
	}

	bool add_double(const char* name, double val) {
		return add_type_double(name, data_type::type_double, val);
	}

	bool add_string(const char* name, const std::string& val) {
		return add_array(name, [&](translate_writer* wr){
			return wr->Int((int)data_type::type_string) && wr->String(val.c_str()); 
		});
	}

	bool add_bool(const char* name, bool val) {
		return add_array(name, [&](translate_writer* wr){
			return wr->Int((int)data_type::type_bool) && wr->Bool(val);
		});
	}
};

//     ,       ）-->           
void test_json_3() {
	translate_writer writer;

	writer.StartObject();
	writer.add_object("msg_header", [](translate_writer* wr){
		wr->add_uint32("len", 123);
		wr->add_uint16("msg_type", 61499);
		wr->add_uint32("user_id", 61493);
		wr->add_uint32("result", 0);
		wr->add_string("md5", "115546546as903aas3l2lakk234k");

		return true;
	});

	writer.add_object("body", [](translate_writer* wr){
		wr->add_uint16("room_id", 102);
		wr->add_uint32("table_id", 4);
		wr->add_float("ratio", 3.141592654);

		return true;
	});

	writer.EndObject();

	std::cout << writer.GetString() << std::endl;
}