c++ 使用rapidjson对数据序列化和反序列化（vs2109）

RapidJSON是腾讯开源的一个高效的C++ JSON解析器及生成器，它是只有头文件的C++库，综合性能是最好的。

安装

在NuGet中为项目安装tencent.rapidjson

引用头文件

#include <rapidjson/document.h>

#include <rapidjson/memorystream.h>

#include <rapidjson/prettywriter.h>

头文件定义

添加测试json字符串和类型对应数组

// 测试json字符串
const char* strJson = "{\"name\":\"MenAngel\",\"age\":23,\"hobbys\":[\"语文\",\"数学\",\"英语\",54],\"scores\":{\"数学\":\"90.6\",\"英语\":\"100.0\", \"语文\":\"80.0\"}}";

// 数据类型，和 rapidjson的enum Type 相对应
static const char* kTypeNames[] = { "Null", "False", "True", "Object", "Array", "String", "Number" };

修改JSON 内容

///

/// 修改JSON 内容
///

void MyRapidJson::alterJson()
{
rapidjson::Document doc;
doc.Parse(strJson);
cout << "修改前： " << strJson <<"\n" << endl;

 // 修改内容

 rapidjson::Value::MemberIterator iter = doc.FindMember("name");
 if (iter != doc.MemberEnd())
     doc["name"] = "张三";

 iter = doc.FindMember("age");
 if (iter != doc.MemberEnd())
 {
     rapidjson::Value& v1 = iter->value;
     v1 = "40";
 }

 // 修改后的内容写入 StringBuffer 中
 rapidjson::StringBuffer buffer;
 rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
 doc.Accept(writer);

 cout <<"修改后： " << buffer.GetString() << "\n" << endl;

}

运行结果：

{"name":"张三","age":"40","hobbys":["语文","数学","英语",54],"scores":{"数学":"90.6","英语":"100.0","语文":"80.0"}}

生成 json 数据

///

/// 生成JSON数据
///

void MyRapidJson::createJson()
{
// 1.准备数据
string name = "王五";
string gender = "boy";
int age = 23;
bool student = true;
vector<string> hobbys = { "语文","数学","英语" };
map<string, double> scores = { {"语文",80},{"数学",90},{"英语",100} };

 //2.初始化DOM
 rapidjson::Document doc;
 rapidjson::Document::AllocatorType& allocator = doc.GetAllocator();
 doc.SetObject();

 // 添加数据
 /* 字符串添加 */ 
 rapidjson::Value tempValue1;
 tempValue1.SetString(name.c_str(), allocator);
 doc.AddMember("name", tempValue1, allocator);

 rapidjson::Value tempValue2(rapidjson::kStringType);
 tempValue2.SetString(gender.c_str(), allocator);
 doc.AddMember(rapidjson::StringRef("gender"), tempValue2, allocator);

 /* 数字类型添加 */
 doc.AddMember("age", age, allocator);

 /* bool 类型 */
 rapidjson::Value tempValueStu(rapidjson::kTrueType);
 tempValueStu.SetBool(student);
 doc.AddMember(rapidjson::StringRef("student"), tempValueStu, allocator);

 /* Array 添加数据 */
 rapidjson::Value tempValue3(rapidjson::kArrayType);
 for (auto hobby : hobbys)
 {
     rapidjson::Value hobbyValue(rapidjson::kStringType);
     hobbyValue.SetString(hobby.c_str(), allocator);
     tempValue3.PushBack(hobbyValue, allocator);
 }
 doc.AddMember("hobbys", tempValue3, allocator);

 /* Object 添加 */
 rapidjson::Value tempValue4(rapidjson::kObjectType);
 tempValue4.SetObject();
 for (auto score : scores)
 {
 	//rapidjson::Value scoreName(rapidjson::kStringType);
 	//scoreName.SetString(score.first.c_str(), allocator);
 	//tempValue4.AddMember(scoreName, score.second, allocator);

     // 方法二
 	rapidjson::Value scoreName(rapidjson::kStringType);
 	scoreName.SetString(score.first.c_str(), allocator);

 	rapidjson::Value scoreValue(rapidjson::kStringType);
     char charValue[20];
     itoa(score.second, charValue,10);
 	scoreValue.SetString(charValue, allocator);
 	tempValue4.AddMember(scoreName, scoreValue, allocator);
 }
 doc.AddMember("scores", tempValue4, allocator);

 // 写入 StringBuffer
 rapidjson::StringBuffer strBuffer;
 rapidjson::Writer<rapidjson::StringBuffer> writer(strBuffer);
 doc.Accept(writer);

 cout << strBuffer.GetString() << "\n" << endl;

 string outFileName = "C:\\Users\\Administrator\\Desktop\\creatJson.txt";
 ofstream outfile(outFileName, std::ios::trunc);
 outfile << strBuffer.GetString() << endl;
 outfile.flush();
 outfile.close();

}

运行结果：

{"name":"王五","gender":"boy","age":23,"student":true,"hobbys":["语文","数学","英语"],"scores":{"数学":"90","英语":"100","语文":"80"}}

json 数据解析

///

/// 查询json 内容
///

void MyRapidJson::searchJson()
{
rapidjson::Document doc;
if (doc.Parse(strJson).HasParseError())
{
std::cout << "json 解析错误" << std::endl;
return;
}

 cout << "doc 的属性成员有 " << doc.MemberCount() << "个!" << endl;

 vector<string> propertyName;
 int i = 0;
 for (rapidjson::Value::MemberIterator iter = doc.MemberBegin(); iter != doc.MemberEnd(); ++iter)
 {
     cout << ++i << "、 " << iter->name.GetString() << "    is " << kTypeNames[iter->value.GetType()] << endl;
     propertyName.push_back(iter->name.GetString());
 }
 cout << endl;

 for (rapidjson::Value::MemberIterator iter = doc.MemberBegin(); iter != doc.MemberEnd(); ++iter)
 {
     if (iter->value.GetType() == rapidjson::kObjectType || iter->value.GetType() == rapidjson::kArrayType)
         cout << iter->name.GetString() << " : " << endl;
     else 
         cout << iter->name.GetString() << " : ";

     DfsDocument(std::move(iter->value));
 }

}

///

/// 遍历里面的内容
///

/// <param name="val"></param>
void MyRapidJson::DfsDocument(rapidjson::Value val)
{
if (!val.GetType())
return;

 switch (val.GetType()) {
 case rapidjson::kNumberType:
 	cout << val.GetInt() << endl;
 	break;
 case rapidjson::kStringType:
 	cout << val.GetString() << endl;
 	break;
 case rapidjson::kArrayType:
 	for (rapidjson::Value::ValueIterator itr = val.GetArray().begin();
 		itr != val.GetArray().end(); ++itr) {
 		rapidjson::Value a;
 		a = *itr;
 		DfsDocument(std::move(a));
 	}
 	break;
 case rapidjson::kObjectType:
 	for (rapidjson::Value::MemberIterator itr = val.GetObject().begin();
 		itr != val.GetObject().end(); ++itr) {
 		cout << itr->name.GetString() << " ";
 		rapidjson::Value a;
 		a = itr->value;
 		DfsDocument(std::move(a));
 	}
 default:
 	break;
 }

}

运行结果

这里需要注意：

object 类型json字符串中，"数字类型" 需转为 "字符串"，否则查询时会报错。

rapidjson 的其他使用方法

///

/// json 属性
///

void MyRapidJson::JsonAttribute()
{
rapidjson::Document doc;
if (doc.Parse(strJson).HasParseError())
{
std::cout << "json 解析错误" << std::endl;
return;
}

 // 成员判断
 if (doc.HasMember("hobbys") && !doc["hobbys"].Empty())
     cout << "doc[\"hobbys\"] is not empty!" << "\n" << endl;
 else
     cout << "doc[\"hobbys\"] 不存在。" << "\n" << endl;

 //7.Array的大小
 if (doc["hobbys"].IsArray())
 {
     cout << "doc[\"hobbys\"].Capacity() =  \"  Array的容量及大小：\" " << doc["hobbys"].Capacity() << " 项" << endl;
     cout << "doc[\"hobbys\"].Size() =  \"  Array的容量及大小：\" " << doc["hobbys"].Size() << " 项" << endl;
 }


 // 字符串长度获取
 cout << doc["name"].GetString()  <<"  字符串长度 ：" << doc["name"].GetStringLength() << endl;

 //4.查询某个成员是否存在
 rapidjson::Value::MemberIterator iter = doc.FindMember("scores");
 if (iter != doc.MemberEnd())
 {
     cout << iter->name.GetString() << " : " << endl;
     DfsDocument(std::move(iter->value));
 }
 else
     cout << "Not Finded!" << endl;

 // 相同判断
 if (doc["name"].GetString() == string("MenAngel") &&
     doc["name"] == "MenAngel" && 
     strcmp(doc["name"].GetString(),"MenAngel") == 0)
 {
     cout << "判断为相等" << endl;
 }

}

运行结果：