5

C++有关RapidJson和Jsoncpp的基本用法

 3 years ago
source link: https://blog.csdn.net/qq_36256590/article/details/115940535
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一. Jsoncpp使用

1.1 Jsoncpp封装

引入头文件：

#include<json/json.h>

示例代码：

int main()
{
	Json::Value JsonRoot;
	Json::FastWriter styleWrite;
	string typenum = "111";
	JsonRoot["TypeNum"] = typenum;
	JsonRoot["NAME"] = "zhangsan";

	Json::Value tempJson;
	tempJson["SEX"] = "male";
	tempJson["AGE"] = 18;
	string info = styleWrite.write(tempJson);
	JsonRoot["INFO"] = info;
	tempJson.clear();

	Json::Value arrJson;
	arrJson["CLASS"] = 001;
	arrJson["TEACHER"] = "Miss Li";
	JsonRoot["Array"].append(arrJson);

	string data = styleWrite.write(JsonRoot);
	cout << data << endl;
	cout << JsonRoot.toStyledString() << endl;
	JsonRoot.clear();
	return 0;
}

输出如下：
在这里插入图片描述

1.2 Jsoncpp解析 
//解析
	Json::Value root;
	Json::Reader reader;
	if (reader.parse(data, root))
	{
		cout << root["INFO"].asString();
		//name 、typenum同理,略
		if (root["Array"].isArray())
		{
			for (size_t i = 0; i < root["Array"].size(); i++)
			{
				cout << root["Array"][i]["CLASS"].asInt() << endl;
				cout << root["Array"][i]["TEACHER"].asString() << endl;
			}
			
		}
	}

额外的话： 附上一个jsoncpp序列化及反序列化博客：C++解析Json

二. RapidJson使用

2.1 基本操作：序列化

添加头文件：

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

string Serialize_1()
{
	rapidjson::StringBuffer strBuf;
	rapidjson::Writer<rapidjson::StringBuffer> writer(strBuf);

	writer.StartObject();
	int count = 0;  //循环写入100次
	while (count < 2000)
	{
		count++;
		//1. 整数类型
		writer.Key("Int");
		writer.Int(1);

		//2. 浮点类型
		writer.Key("Double");
		writer.Double(12.0000001);

		//3. 字符串类型
		writer.Key("String");
		writer.String("This is a string");

		//4. 结构体类型
		writer.Key("Object");
		writer.StartObject();
		writer.Key("name");
		writer.String("qq849635649");
		writer.Key("age");
		writer.Int(25);
		writer.EndObject();

		//5. 数组类型
		//5.1 整型数组
		writer.Key("IntArray");
		writer.StartArray();
		//顺序写入即可
		writer.Int(10);
		writer.Int(20);
		writer.Int(30);
		writer.EndArray();

		//5.2 浮点型数组
		writer.Key("DoubleArray");
		writer.StartArray();
		for (int i = 1; i < 4; i++)
		{
			writer.Double(i * 1.0);
		}
		writer.EndArray();

		//5.3 字符串数组
		writer.Key("StringArray");
		writer.StartArray();
		writer.String("one");
		writer.String("two");
		writer.String("three");
		writer.EndArray();

		//5.4 混合型数组
		//这说明了，一个json数组内容是不限制类型的
		writer.Key("MixedArray");
		writer.StartArray();
		writer.String("one");
		writer.Int(50);
		writer.Bool(false);
		writer.Double(12.005);
		writer.EndArray();

		//5.5 结构体数组
		writer.Key("People");
		writer.StartArray();
		for (int i = 0; i < 3; i++)
		{
			writer.StartObject();
			writer.Key("name");
			writer.String("qq849635649");
			writer.Key("age");
			writer.Int(i * 10);
			writer.Key("sex");
			writer.Bool((i % 2) == 0);
			writer.EndObject();
		}
		writer.EndArray();
	}
	writer.EndObject();

	string data = strBuf.GetString();
	return data;
}
2.2 反序列化

添加头文件：

#include "rapidjson/document.h"

void deSerialize_l()
{
	string data =
		"{\"Int\":1,"
		"\"Double\":12.0000001,"
		"\"String\":\"This is a string\","
		"\"Object\":{\"name\":\"qq849635649\",\"age\":25},"
		"\"IntArray\":[10,20,30],"
		"\"DoubleArray\":[1.0,2.0,3.0],"
		"\"StringArray\":[\"one\",\"two\",\"three\"],"
		"\"MixedArray\":[\"one\",50,false,12.005],"
		"\"People\":[{\"name\":\"qq849635649\",\"age\":0,\"sex\":true},"
		"{\"name\":\"qq849635649\",\"age\":10,\"sex\":false},"
		"{\"name\":\"qq849635649\",\"age\":20,\"sex\":true}]}";

		//创建解析对象
		rapidjson::Document doc;
		//首先进行解析，没有解析错误才能进行具体字段的解析
		if (!doc.Parse(data.data()).HasParseError())
		{
			//1. 解析整数
			if (doc.HasMember("Int") && doc["Int"].IsInt())
			{
				cout << "Int = " << doc["Int"].GetInt() << endl;
			}
			//2. 解析浮点型
			if (doc.HasMember("Double") && doc["Double"].IsDouble())
			{
				cout << "Double = " << doc["Double"].GetDouble() << endl;
			}
			//3. 解析字符串
			if (doc.HasMember("String") && doc["String"].IsString())
			{
				cout << "String = " << doc["String"].GetString() << endl;
			}
			//4. 解析结构体
			if (doc.HasMember("Object") && doc["Object"].IsObject())
			{
				const rapidjson::Value& object = doc["Object"];
				if (object.HasMember("name") && object["name"].IsString())
				{
					cout << "Object.name = " << object["name"].GetString() << endl;
				}
				if (object.HasMember("age") && object["age"].IsInt())
				{
					cout << "Object.age = " << object["age"].GetInt() << endl;
				}
			}
			//5. 解析数组类型
			//5.1 整型数组类型
			if (doc.HasMember("IntArray") && doc["IntArray"].IsArray())
			{
				//5.1.1 将字段转换成为rapidjson::Value类型
				const rapidjson::Value& array = doc["IntArray"];
				//5.1.2 获取数组长度
				size_t len = array.Size();
				//5.1.3 根据下标遍历，注意将元素转换为相应类型，即需要调用GetInt()
				for (size_t i = 0; i < len; i++)
				{
					cout << "IntArray[" << i << "] = " << array[i].GetInt() << endl;
				}
			}
			//5.2 浮点型数组类型
			if (doc.HasMember("DoubleArray") && doc["DoubleArray"].IsArray())
			{
				const rapidjson::Value& array = doc["DoubleArray"];
				size_t len = array.Size();
				for (size_t i = 0; i < len; i++)
				{
					//为防止类型不匹配，一般会添加类型校验
					if (array[i].IsDouble())
					{
						cout << "DoubleArray[" << i << "] = " << array[i].GetDouble() << endl;
					}
				}
			}
			//5.3 字符串数组类型
			if (doc.HasMember("StringArray") && doc["StringArray"].IsArray())
			{
				const rapidjson::Value& array = doc["StringArray"];
				size_t len = array.Size();
				for (size_t i = 0; i < len; i++)
				{
					//为防止类型不匹配，一般会添加类型校验
					if (array[i].IsString())
					{
						cout << "StringArray[" << i << "] = " << array[i].GetString() << endl;
					}
				}
			}
			//5.4 混合型
			if (doc.HasMember("MixedArray") && doc["MixedArray"].IsArray())
			{
				const rapidjson::Value& array = doc["MixedArray"];
				size_t len = array.Size();
				for (size_t i = 0; i < len; i++)
				{
					//为防止类型不匹配，一般会添加类型校验
					if (array[i].IsString())
					{
						cout << "MixedArray[" << i << "] = " << array[i].GetString() << endl;
					}
					else if (array[i].IsBool())
					{
						cout << "MixedArray[" << i << "] = " << array[i].GetBool() << endl;
					}
					else if (array[i].IsInt())
					{
						cout << "MixedArray[" << i << "] = " << array[i].GetInt() << endl;
					}
					else if (array[i].IsDouble())
					{
						cout << "MixedArray[" << i << "] = " << array[i].GetDouble() << endl;
					}
				}
			}
			//5.5 结构体数组类型
			if (doc.HasMember("People") && doc["People"].IsArray())
			{
				const rapidjson::Value& array = doc["People"];
				size_t len = array.Size();
				for (size_t i = 0; i < len; i++)
				{
					const rapidjson::Value& object = array[i];
					//为防止类型不匹配，一般会添加类型校验
					if (object.IsObject())
					{
						cout << "ObjectArray[" << i << "]: ";
						if (object.HasMember("name") && object["name"].IsString())
						{
							cout << "name=" << object["name"].GetString();
						}
						if (object.HasMember("age") && object["age"].IsInt())
						{
							cout << ", age=" << object["age"].GetInt();
						}
						if (object.HasMember("sex") && object["sex"].IsBool())
						{
							cout << ", sex=" << (object["sex"].GetBool() ? "男" : "女") << endl;
						}
					}
				}
			}
		}
		/**
		 *    最后注意：因为rapidjson不会做安全校验，所以要自己做安全校验，以int整型为例
		 * “if(object.HasMember("age") && object["age"].IsInt()) {}”
		 * 这句校验很重要，既要校验有该子段，也要校验类型正确，否则会引发程序崩溃
		 */
}

总结：之前有大致测试过几M的数据，jsoncpp解析大致时间10ms，而RapidJson解析时间不到它的一半。建议使用rapidjson。


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