json 对c++类的序列化(自动生成代码)

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【动机】

之前写网络协议的时候，使用的是google protobuf，protobuf不但在性能和扩展性上有很好的优势，protoc自动生成c++类代码的工具，这点确实给程序员带来了很多便利。

做后面一项目使用的json格式来传输，然后就萌生了实现像protoc这样的工具，根据json文件来生成c++类代码，并且生成序列化代码，这样在写网络的时候就无需把jsonvalue序列化散落在各处。

【思路】

之前写object-c的时候，如果你要对类的序列化，你必须实现NSCoding协议(接口), 这样的实现方式很友好，同样，我的方式则是参考NSCoding的，

【Code】

我这里借鉴网友的一个json序列化实现方式，感觉这种方式很方便，他是通过模板来实现对内置类型的识别，而且对所有的类型都使用了统一接口：

/*
* Copyright (c) 2011-2012 Promit Roy
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
//////////////////////////////////////////////////////////////
// From: http://ventspace.wordpress.com/2012/10/08/c-json-serialization/
// FileName: json_serializer_helper.hpp
// Modify: Sachin
// Date: 2013/9/22 13:41
// Description:
//
// History:
// <author> <time> <descript>
// Sachin 2013/9/22 add
//////////////////////////////////////////////////////////////#ifndef JSON_SERIALIZER_HELPER_HPP
#define JSON_SERIALIZER_HELPER_HPP
#include <lib_json/json_lib.h>
#include <boost/utility.hpp>
#include <boost/type_traits.hpp>
#include <string>
#include <assert.h>#define NVP(name) #name, name
#define SerializeNVP(name) Serialize(NVP(name))#define DeSerializeNVP(name) DeSerialize(NVP(name))class JsonSerializerHelper {
private:
//SFINAE garbage to detect whether a type has a Serialize member
struct serialize_not_found {};
typedef serialize_not_found SerializeNotFound;
struct SerializeFound { char x[]; }; template<typename T, void (T::*)(JsonSerializerHelper&) const>
struct SerializeTester { }; template<typename T>
static SerializeFound SerializeTest(SerializeTester<T, &T::Serialize>*);
template<typename T>
static SerializeNotFound SerializeTest(...); template<typename T>
struct HasSerialize
{
static const bool value = sizeof(SerializeTest<T>()) == sizeof(SerializeFound);
}; //Serialize using a free function defined for the type (default fallback)
template<typename TValue>
void SerializeImpl(const TValue& value,
typename boost::disable_if<HasSerialize<const TValue> >::type* dummy = )
{
//prototype for the serialize free function, so we will get a link error if it's missing
//this way we don't need a header with all the serialize functions for misc types (eg math)
void SerializeFail(const TValue&, JsonSerializerHelper&); SerializeFail(value, *this);
} //Serialize using a member function Serialize(JsonSerializer&)
template<typename TValue>
void SerializeImpl(const TValue& value, typename boost::enable_if<HasSerialize<const TValue> >::type* dummy = )
{
value.Serialize(*this);
} private:
//
struct deserialize_not_found {};
typedef deserialize_not_found DeSerializeNotFound; struct DeSerializeFound { char x[]; }; template<typename T, void (T::*)(const JsonSerializerHelper&)>
struct DeSerializeTester { };
template<typename T>
static DeSerializeFound DeSerializeTest(DeSerializeTester<T, &T::DeSerialize>*);
template<typename T>
static DeSerializeNotFound DeSerializeTest(...); template<typename T>
struct HasDeSerialize
{
static const bool value = sizeof(DeSerializeTest<T>()) == sizeof(DeSerializeFound);
}; //Serialize using a free function defined for the type (default fallback)
template<typename TValue>
void DeSerializeImpl(TValue& value,
typename boost::disable_if<HasDeSerialize<TValue> >::type* dummy = ) const
{
void DeSerializeFail(TValue&, const JsonSerializerHelper&); DeSerializeFail(value, *this);
} //Serialize using a member function Serialize(JsonSerializer&)
template<typename TValue>
void DeSerializeImpl(TValue& value, typename boost::enable_if<HasDeSerialize<TValue> >::type* dummy = ) const
{
value.DeSerialize(*this);
}
public:
JsonSerializerHelper()
{ } template<typename TKey, typename TValue>
void Serialize(TKey key, const TValue& value, typename boost::enable_if<boost::is_class<TValue> >::type* dummy = )
{
// class to json
JsonSerializerHelper subVal;
subVal.SerializeImpl(value);
JsonValue[key] = subVal.JsonValue;
} template<typename TKey, typename TValue>
void DeSerialize(TKey key, TValue& value, typename boost::enable_if<boost::is_class<TValue> >::type* dummy = ) const
{
// json to class
JsonSerializerHelper subVal;
subVal.JsonValue = JsonValue[key];
subVal.DeSerializeImpl(value);
} template<typename TKey>
void Serialize(TKey key, const Json::Value& value)
{
Write(key, value);
} template<typename TKey>
void DeSerialize(TKey key, Json::Value& value) const
{
Read(key, value);
}
//Serialize a string value
template<typename TKey>
void Serialize(TKey key, const std::string& value)
{
Write(key, value);
} //DeSerialize a string value
template<typename TKey>
void DeSerialize(TKey key, std::string& value) const
{
Read(key, value);
} //Serialize a non class type directly using JsonCpp
template<typename TKey, typename TValue>
void Serialize(TKey key, const TValue& value, typename boost::enable_if<boost::is_fundamental<TValue> >::type* dummy = )
{
Write(key, value);
} template<typename TKey, typename TValue>
void DeSerialize(TKey key, TValue& value, typename boost::enable_if<boost::is_fundamental<TValue> >::type* dummy = ) const
{
Read(key, value);
} //Serialize an enum type to JsonCpp
template<typename TKey, typename TEnum>
void Serialize(TKey key, const TEnum& value, typename boost::enable_if<boost::is_enum<TEnum> >::type* dummy = )
{
int ival = (int) value;
Write(key, ival);
} template<typename TKey, typename TEnum>
void DeSerialize(TKey key, TEnum& value, typename boost::enable_if<boost::is_enum<TEnum> >::type* dummy = ) const
{
int ival = (int) value;
Read(key, ival);
value = (TEnum) ival;
} template<typename TKey, typename TValue>
void Serialize(TKey key, const std::vector<TValue>& vec)
{
Write(key, vec.begin(), vec.end());
} template<typename TKey, typename TValue>
void DeSerialize(TKey key, std::vector<TValue>& vec) const
{
JsonSerializerHelper subVal;
subVal.JsonValue = JsonValue[key];
subVal.Read(vec);
} Json::Value JsonValue;private:
template<typename TKey, typename TValue>
void Write(TKey key, const TValue& value)
{
JsonValue[key] = value;
} template<typename TKey, typename TValue>
void Write(TKey key, const std::vector<TValue>& vec)
{ JsonSerializerHelper subVal;
int index = ;
for(typename std::vector<TValue>::const_iterator it = vec.begin(); it != vec.end(); ++it)
{
subVal.Serialize(index, *it);
++index;
}
JsonValue[key] = subVal.JsonValue;
} template<typename TKey, typename TItor>
void Write(TKey key, TItor first, TItor last)
{
JsonSerializerHelper subVal;
int index = ;
for(TItor it = first; it != last; ++it)
{
subVal.Serialize(index, *it);
++index;
}
JsonValue[key] = subVal.JsonValue;
} template<typename TKey, typename TValue>
void Read(TKey key, TValue& value, typename boost::enable_if<boost::is_arithmetic<TValue> >::type* dummy = ) const
{
int ival = ;
if (JsonValue[key].isNumeric()){
ival = JsonValue[key].asInt();
} else {
//assert(false);
}
value = (TValue) ival;
} template<typename TKey, typename TValue>
void Read(TKey key, TValue& value) const
{
value = JsonValue[key];
} template<typename TKey>
void Read(TKey key, bool& value) const
{
bool bval = false ;
bval = JsonValue[key].asBool();
value = bval;
} template<typename TKey>
void Read(TKey key, int& value) const
{
int ival = ;
if (JsonValue[key].isNumeric()){
ival = JsonValue[key].asInt();
} else if (JsonValue[key].isString()){
ival = atoi(JsonValue[key].asCString());
} else {
//assert(false);
}
value = ival;
} template<typename TKey>
void Read(TKey key, unsigned int& value) const
{
unsigned int uival = ;
if (JsonValue[key].isNumeric()){
uival = JsonValue[key].asUInt();
} else if (JsonValue[key].isString()){
uival = atoi(JsonValue[key].asCString());
} else {
//assert(false);
}
value = uival;
} template<typename TKey>
void Read(TKey key, float& value) const
{
float fval = 0.0 ;
if (JsonValue[key].isNumeric()){
fval = JsonValue[key].asFloat();
} else if (JsonValue[key].isString()){
fval = atof(JsonValue[key].asCString());
} else {
//assert(false);
}
value = fval;
} template<typename TKey>
void Read(TKey key, double& value) const
{
double dval = 0.0 ;
if (JsonValue[key].isNumeric()){
dval = JsonValue[key].asDouble();
} else if (JsonValue[key].isString()){
dval = atof(JsonValue[key].asCString());
} else {
//assert(false);
}
value = dval;
} template<typename TKey>
void Read(TKey key, std::string& value) const
{
std::string sval = "" ;
if (JsonValue[key].isString()){
sval = JsonValue[key].asString();
} else {
//assert(false);
}
value = sval;
} template<typename TValue>
void Read(std::vector<TValue>& vec) const
{
if(!JsonValue.isArray())
return; vec.clear();
vec.reserve(vec.size() + JsonValue.size());
for(int i = ; i < JsonValue.size(); ++i)
{
TValue val;
DeSerialize(i, val);
vec.push_back(val);
}
}
};
#endif //JSON_SERIALIZER_HELPER_HPP

我对原来的基础上进行了稍微改良，把DeSerialize 和Serialize分离了，每个类需要实现这两个接口，这个工具通过函数重载模板匹配对序列化做了统一的接口

【生成Cpp代码】

我们对json文件进行解析，json的dict对应c++的类，字典类的某个字段相应的类型对应c++类型，用key值作为class类型名，

【样例】

json

{
"image": {
"width": 800,
"height": 600,
"title": "View from 15th Floor",
"thumbnail": {
"url": "http://www.example.com/image/481989943",
"height": 125,
"width": "100"
},
"ids": [116, 943, 234, 38793]
}
}

c++ cpp

// Don't Edit it
#ifndef TEST_H_
#define TEST_H_#include <string>
#include <vector>
#include <lib_json/json_lib.h>class JsonSerializerHelper;namespace net {
namespace test {class Thumbnail {
public:
Thumbnail();
~Thumbnail(){} const std::string& get_url() { return url;}
const std::string& get_url() const { return url;}
void set_url(const std::string& url_a) {
url = url_a;
} const std::string& get_width() { return width;}
const std::string& get_width() const { return width;}
void set_width(const std::string& width_a) {
width = width_a;
} const int& get_height() { return height;}
const int& get_height() const { return height;}
void set_height(const int& height_a) {
height = height_a;
} void Serialize(JsonSerializerHelper& json_serializer_helper) const;
void DeSerialize(const JsonSerializerHelper& json_serializer_helper); private:
std::string url;
std::string width;
int height;}; // class Thumbnailclass Image {
public:
Image();
~Image(){} const std::vector<int>& get_ids() { return ids;}
const std::vector<int>& get_ids() const { return ids;}
void set_ids(const std::vector<int>& ids_a) {
ids = ids_a;
} const int& get_width() { return width;}
const int& get_width() const { return width;}
void set_width(const int& width_a) {
width = width_a;
} const std::string& get_title() { return title;}
const std::string& get_title() const { return title;}
void set_title(const std::string& title_a) {
title = title_a;
} Thumbnail& get_thumbnail() { return thumbnail;}
const Thumbnail& get_thumbnail() const { return thumbnail;}
void set_thumbnail(const Thumbnail& thumbnail_a) {
thumbnail = thumbnail_a;
} const int& get_height() { return height;}
const int& get_height() const { return height;}
void set_height(const int& height_a) {
height = height_a;
} void Serialize(JsonSerializerHelper& json_serializer_helper) const;
void DeSerialize(const JsonSerializerHelper& json_serializer_helper); private:
std::vector<int> ids;
int width;
std::string title;
Thumbnail thumbnail;
int height;}; // class Imageclass Test {
public:
Test();
~Test(){} Image& get_image() { return image;}
const Image& get_image() const { return image;}
void set_image(const Image& image_a) {
image = image_a;
} void Serialize(JsonSerializerHelper& json_serializer_helper) const;
void DeSerialize(const JsonSerializerHelper& json_serializer_helper); private:
Image image;}; // class Test} // namespace test
} // namespace net
#endif // TEST_H_

//Don't Edit it#include "test.h"
#include "network/net_util/json_serializer_helper.hpp"namespace net {
namespace test {Thumbnail::Thumbnail(): height(){
}void Thumbnail::Serialize(
JsonSerializerHelper& json_serializer_helper) const {
json_serializer_helper.SerializeNVP(url);
json_serializer_helper.SerializeNVP(width);
json_serializer_helper.SerializeNVP(height);
}void Thumbnail::DeSerialize(
const JsonSerializerHelper& json_serializer_helper) {
json_serializer_helper.DeSerializeNVP(url);
json_serializer_helper.DeSerializeNVP(width);
json_serializer_helper.DeSerializeNVP(height);
}Image::Image(): width(),
height(){
}void Image::Serialize(
JsonSerializerHelper& json_serializer_helper) const {
json_serializer_helper.SerializeNVP(ids);
json_serializer_helper.SerializeNVP(width);
json_serializer_helper.SerializeNVP(title);
json_serializer_helper.SerializeNVP(thumbnail);
json_serializer_helper.SerializeNVP(height);
}void Image::DeSerialize(
const JsonSerializerHelper& json_serializer_helper) {
json_serializer_helper.DeSerializeNVP(ids);
json_serializer_helper.DeSerializeNVP(width);
json_serializer_helper.DeSerializeNVP(title);
json_serializer_helper.DeSerializeNVP(thumbnail);
json_serializer_helper.DeSerializeNVP(height);
}Test::Test(){
}void Test::Serialize(
JsonSerializerHelper& json_serializer_helper) const {
json_serializer_helper.SerializeNVP(image);
}void Test::DeSerialize(
const JsonSerializerHelper& json_serializer_helper) {
json_serializer_helper.DeSerializeNVP(image);
}} // namespace test
} // namespace net