JsonCpp经典入门

1.JsonCpp

1.1.JsonCpp简介

JSON is a lightweight data-interchange format. It can represent numbers,strings,ordered sequences of values,and collections of name/value pairs.

JsonCpp is a C++ library that allows manipulating JSON values,including serialization and deserialization to and from strings. It can also preserve existing comment in unserialization/serialization steps,making it a convenient format to store user input files.

1.2.JsonCpp环境搭建

1.2.1.下载地址

https://github.com/open-source-parsers/jsoncpp#generating-amalgamated-source-and-header

1.2.2.Qt中JsonCpp安装

①　解压jsoncpp-master.zip包
②　在根目录下，运行python amalgamate.py
③　在根目录中生成dist文件夹包含三个文件dist/json/json-forwards.h dist/json/json.h dist/json.cpp
④　在Qt工程目录下，生成json文件夹，并拷贝json目录下。
⑤　在Qt工程中添加现有文件即可。

1.3.读写JsonCpp

1.3.1.写

#include <iostream>
#include <fstream>
#include "json/json.h"
using namespace Json;
using namespace std;


#if 0
{
    "animals":{
    "dog":[
        {
            "name":"Rufus","age":15
        },{
            "name":"Marty","age":null
        }
        ]
    }
}
#endif

void writeJson()
{
    Value  rootAnimalsObj;
    Value dog;
    Value  dogArray;

    Value  dogValueItem1;
    dogValueItem1["name"] = "Rufus";
    dogValueItem1["age"]  = 15;

    Value  dogValueItem2;
    dogValueItem2["name"] = "Marty";
    dogValueItem2["age"]  = "";

    dogArray.append(dogValueItem1);
    dogArray.append(dogValueItem2);
    dog["dog"] = dogArray;
    rootAnimalsObj["animals"] = dog;

    string str = rootAnimalsObj.toStyledString();
    cout<<str;

    ofstream ofs;
    ofs.open("test_write.json");
    ofs << str;
    ofs.close();

    return;
}

int main()
{
    writeJson();
    return 0;
}

1.3.2.读

#include <iostream>
#include <fstream>
#include "json/json.h"
using namespace Json;
using namespace std;


#if 0
{
    "animals":{
    "dog":[
        {
            "name":"Rufus","age":null
        }
        ]
    }
}
#endif



void readJson()
{
    ifstream is("aa.json");
    if(!is)
    {
        cout<<"open error"<<endl;
        return;
    }
    Reader reader;
    Value root;

    if(reader.parse(is,root))
    {
        cout<<root<<endl;
        Value & dogArr = root["animals"]["dog"];
        for(int i=0; i<dogArr.size(); i++)
        {
            cout<<dogArr[i]["name"].asString()<<endl;
            cout<<dogArr[i]["age"].asInt()<<endl;
        }

    }

    is.close();
}

int main()
{
    readJson();
    return 0;
}