boost库json 的所有用法

Boost库的JSON模块提供了一组用于处理JSON数据的工具和类。以下是Boost库JSON的常见用法：

1. 解析JSON数据

使用json::parse()函数将JSON字符串解析为JSON对象：

#include <boost/json.hpp>
#include <iostream>

int main()
{
    std::string json_str = R"(
        {
            "name": "John",
            "age": 30,
            "is_student": true,
            "address": {
                "street": "123 Main St",
                "city": "Anytown",
                "state": "CA"
            },
            "scores": [85, 90, 92]
        }
    )";

    boost::json::value json_obj = boost::json::parse(json_str);

    std::cout << json_obj << std::endl;

    return 0;
}

2. 获取JSON对象的值

使用json::value的成员函数获取JSON对象的键和值：

#include <boost/json.hpp>
#include <iostream>

int main()
{
    std::string json_str = R"(
        {
            "name": "John",
            "age": 30,
            "is_student": true,
            "address": {
                "street": "123 Main St",
                "city": "Anytown",
                "state": "CA"
            },
            "scores": [85, 90, 92]
        }
    )";

    boost::json::value json_obj = boost::json::parse(json_str);

    std::string name = json_obj.at("name").as_string().data();
    int age = json_obj.at("age").as_int64();
    bool is_student = json_obj.at("is_student").as_bool();
    std::string street = json_obj.at("address").as_object().at("street").as_string().data();
    int score1 = json_obj.at("scores").as_array()[0].as_int64();

    std::cout << "Name: " << name << std::endl;
    std::cout << "Age: " << age << std::endl;
    std::cout << "Is student: " << is_student << std::endl;
    std::cout << "Street: " << street << std::endl;
    std::cout << "Score 1: " << score1 << std::endl;

    return 0;
}

3. 构造JSON对象

使用json::value构造函数或json::value的成员函数构造JSON对象：

#include <boost/json.hpp>
#include <iostream>

int main()
{
    boost::json::object obj {
        {"name", "John"},
        {"age", 30},
        {"is_student", true},
        {"address", {
            {"street", "123 Main St"},
            {"city", "Anytown"},
            {"state", "CA"}
        }},
        {"scores", {85, 90, 92}}
    };

    boost::json::value json_obj(obj);

    std::cout << json_obj << std::endl;

    return 0;
}

4. 修改JSON对象的值

使用json::value的成员函数修改JSON对象的值：

#include <boost/json.hpp>
#include <iostream>

int main()
{
    std::string json_str = R"(
        {
            "name": "John",
            "age": 30,
            "is_student": true,
            "address": {
                "street": "123 Main St",
                "city": "Anytown",
                "state": "CA"
            },
            "scores": [85, 90, 92]
        }
    )";

    boost::json::value json_obj = boost::json::parse(json_str);

    json_obj.as_object()["name"] = "Jane";
    json_obj.as_object()["age"] = 35;
    json_obj.as_object()["is_student"] = false;
    json_obj.as_object()["address"].as_object()["street"] = "456 Elm St";
    json_obj.as_object()["scores"].as_array()[1] = 95;

    std::cout << json_obj << std::endl;

    return 0;
}

5. 序列化JSON对象

使用json::to_string()函数将JSON对象序列化为JSON字符串：

#include <boost/json.hpp>
#include <iostream>

int main()
{
    std::string json_str = R"(
        {
            "name": "John",
            "age": 30,
            "is_student": true,
            "address": {
                "street": "123 Main St",
                "city": "Anytown",
                "state": "CA"
            },
            "scores": [85, 90, 92]
        }
    )";

    boost::json::value json_obj = boost::json::parse(json_str);
    std::string serialized_json = boost::json::to_string(json_obj);

    std::cout << serialized_json << std::endl;

    return 0;
}