Linux环境下 C++ jsoncpp教程

1、cmake安装

git clone https://github.com/open-source-parsers/jsoncpp.git
cd jsoncpp 
mkdir -p build
cd build
cmake -DCMAKE_BUILD_TYPE=release -DBUILD_STATIC_LIBS=ON -DBUILD_SHARED_LIBS=OFF -DARCHIVE_INSTALL_DIR=. -G "Unix Makefiles" ..
make 
sudo make install

2、使用

添加头文件json.h 

#include <./jsoncpp/include/json/json.h>b

 编译时使用动态库，添加

g++ -ljsoncpp

3、示例代码

3.1 从文件/字符串读入json数据

alice.cpp

#include <iostream>
#include <fstream>
#include <string>
#include </home/clay/jsoncpp/include/json/json.h>
using namespace std;

int main() {
    ifstream ifs("alice.json");
    Json::Reader reader;
    Json::Value obj;
    reader.parse(ifs, obj); // reader can also read strings
    cout << "Book: " << obj["book"].asString() << endl;
    cout << "Year: " << obj["year"].asUInt() << endl;
    const Json::Value& characters = obj["characters"]; // array of characters
    for (int i = 0; i < characters.size(); i++){
        cout << "    name: " << characters[i]["name"].asString();
        cout << " chapter: " << characters[i]["chapter"].asUInt();
        cout << endl;
    }
    //read from string
    string alice_json=R"({"Age":22,"Name":"Clay"})";
    Json::Reader re_ali;
    Json::Value ob_ali;
    re_ali.parse(alice_json,ob_ali);
    cout<<"Age="<<ob_ali["Age"].asInt()<<endl;
    cout<<"Name="<<ob_ali["Name"].asString()<<endl;
    return 0;
}

　alice.json文件

{
    "book":"Alice in Wonderland",
    "year":1865,
    "characters":
    [
        {"name":"Jabberwock", "chapter":1},
        {"name":"Cheshire Cat", "chapter":6},
        {"name":"Mad Hatter", "chapter":7}
    ]
}

3.2 向文件/字符串读入json数据

　writedemo.cpp

#include <iostream>
#include <fstream>
#include </home/clay/jsoncpp/include/json/json.h>
using namespace std;

int main()
{
       //根节点
    Json::Value root;

    //根节点属性
    root["name"] = Json::Value("shuiyixin");
    root["age"] = Json::Value(21);
    root["sex"] = Json::Value("man");

    //子节点
    Json::Value friends;

    //子节点属性
    friends["friend_name"] = Json::Value("ZhaoWuxian");
    friends["friend_age"] = Json::Value(21);
    friends["friend_sex"] = Json::Value("man");

    //子节点挂到根节点上
    root["friends"] = Json::Value(friends);

    //数组形式
    root["hobby"].append("sing");
    root["hobby"].append("run");
    root["hobby"].append("Tai Chi");

    //直接输出
    cout << "FastWriter:" << endl;
    Json::FastWriter fw;
    cout << fw.write(root) << endl << endl;

    //缩进输出
    cout << "StyledWriter:" << endl;
    Json::StyledWriter sw;
    cout << sw.write(root) << endl << endl;

    //输出到字符串
    string jsonstr = sw.write(root);
    cout << jsonstr << endl;

    //输出到文件
    ofstream os;
    os.open("demo.json");
    if (!os.is_open())
        cout << "error：can not find or create the file which named \" demo.json\"." << endl;
    os << sw.write(root);
    os.close();
    return 0;
}

 Reference:

https://www.cnblogs.com/__tudou__/p/14957646.html;

https://en.wikibooks.org/wiki/JsonCpp#Example;

https://github.com/open-source-parsers/jsoncpp;

https://blog.csdn.net/shuiyixin/article/details/89330529。