JsonCpp 的使用

Json::Reader *pJsonParser = new Json::Reader(Json::Features::strictMode());

1.value.isMember("key");    //存在返回true,否则为false
2.value["sex"].isNull();    //为NULL返回1,否则为0

#include <iostream>
#include <sstream>
#include <fstream>
#include <json/json.h>

void readJsonFromFile()
{
    std::ifstream ifs;
    ifs.open("a.json");
    std::stringstream buffer;
    buffer << ifs.rdbuf();
    ifs.close();

    auto str = buffer.str();

    Json::Reader reader;
    Json::Value value;
    if (reader.parse(str,value)) {
        //节点判断
        std::cout << "value‘s empty:" << value.empty() << std::endl;
        std::cout << "name is string:" << value["name"].isString() << std::endl;
        std::cout << "age is string:" << value["age"].isString() << std::endl;

        //类型获取
        std::cout << "name‘s type:" << value["name"].type() << std::endl;
        std::cout << "like‘s type:" << value["like"].type() << std::endl;

        //类型转换
        //根据Key获取值时最好判断类型,否则解析会中断
        std::cout << "name:" << value["name"].asString() << std::endl;
        std::cout << "age:" << value["age"].asInt() << std::endl;

        //节点获取
        std::cout << value["job"] << std::endl;                        //[]方式获取
        std::cout << value.get("name","dxx") << std::endl;            //get方式获取
        std::cout << value.isMember("job") << std::endl;
        std::cout << "value‘s obj:" << value.isObject() << std::endl;
        std::cout << "like‘s obj:" << value["like"].isObject() << std::endl;

        std::cout << "like.size:" << value["like"].size() << std::endl;
        std::cout << "like[0][food]:" << value["like"][0]["food"].asString() << std::endl;

        //节点操作
        std::cout << "name compare age:" << value["name"].compare("age") << std::endl;
        value["name"] = "swduan";            //修改
        value["address"] = "hz";             //增加
        value["phone"] = "10086";        
        value.removeMember("age");           //删除
        value["like"][0]["sport"] = "game";  //往value["like"]中添加一项元素

        Json::Value item;
        item["hate"] = "game";
        value["like"].append(item);            //value["like"]中再添加一维数组
        std::cout << "value[\"like\"]‘s size:" << value["like"].size() << std::endl;
        
        std::cout << "--------------------" << std::endl;
        std::cout << value.toStyledString() << std::endl;

        std::cout << "--------------------" << std::endl;
        auto all_member = value.getMemberNames();
        for (auto member : all_member) {
            std::cout << member << std::endl;
        }

        std::cout << "--------------------" << std::endl;
        value.clear();        //清空元素
        std::cout << value.toStyledString() << std::endl;
    }
}

void jsonWriteToFile()
{
    Json::FastWriter write;
    Json::Value root;

    Json::Value item;
    Json::Value arrayObj;
    item["book"] = "c++";
    item["food"] = "apple";
    item["music"] = "ddx";
    arrayObj.append(item);

    root["name"] = "dsw";
    root["age"]  = 18;
    root["like"] = arrayObj;    //注意:这里不能用append,append功能是将Json::Value添加到数组末尾

    auto str = root.toStyledString();
    std::cout << str << std::endl;

    std::ofstream ofss;
    ofss.open("a.json");
    ofss << str;
    ofss.close();
}

int main()
{
    jsonWriteToFile();
    readJsonFromFile();

    getchar();
    return 0;
}

value‘s empty:0
name is string:1
age is string:0
name‘s type:4
like‘s type:6
name:dsw
age:18
null
"dsw"
value‘s obj:1
like‘s obj:0
like.size:1
like[0][food]:apple
name compare age:1
value["like"]‘s size:2
--------------------
{
   "address" : "hz","job" : null,"like" : [
      {
         "book" : "c++","food" : "apple","music" : "ddx","sport" : "game"
      },{
         "hate" : "game"
      }
   ],"name" : "swduan","phone" : "10086"
}

--------------------
address
job
like
name
phone
--------------------
{}