如何使用C++中的boost庫將類對象轉換為json字符串？

Question

我對 C++ 相當陌生，如果您覺得這很容易，我會事先道歉。

我有以下文件POST1.h

#ifndef POST1_HH
#define POST1_HH

#include <iostream>

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>

using namespace std ;
using boost::property_tree::ptree;
using boost::property_tree::read_json;
using boost::property_tree::write_json;
using boost::property_tree::basic_ptree;

#include "DBAccess2.h"

class POST1
{

    public:
    string TokenNo;
    string CommandStatus;
    string CommandID;
    string CPUID;
    string ISEncrypted;
    string JSON_Cmnd_String;

    void POST_Device_Status(sqliteDB & DB_OBJ);

};

#endif

下面是POST1.cpp

#include <iostream>
#include <sstream>

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>

#include "DBAccess2.h"
#include "POST1.h"

using namespace std ;
using boost::property_tree::ptree;
using boost::property_tree::read_json;
using boost::property_tree::write_json;
using boost::property_tree::basic_ptree;

void POST1::POST_Device_Status(sqliteDB & DB_OBJ)
{
    POST1 POST_OBJ;

    POST_OBJ.TokenNo = "1122";
    POST_OBJ.CommandStatus = "0";
    POST_OBJ.CommandID = "00";
    POST_OBJ.CPUID = "A1234B1234";
    POST_OBJ.ISEncrypted = "0";
    POST_OBJ.JSON_Cmnd_String = DB_OBJ.dump(DB_OBJ);
}

筆記：-

(1) sqliteDB 是在 .cpp 文件中聲明的另一個類。

(2)函數 dump( )的輸出是一個 json 字符串。 這被存儲到 JSON_Cmnd_string 中。

所以，我想將類對象轉換為 JSON 字符串，我該怎么做？ 我是否必須先將這些對象放入容器（如向量或列表）中，然后再將其寫入 JSON？

Answer 1

這不是“相當容易”，因為C ++沒有JSON支持。

Boost也沒有：

• 如何讓json使用正確的數據類型

也就是說，這似乎是你想要的：

• http://www.boost.org/doc/libs/1_57_0/doc/html/boost_propertytree/tutorial.html

所以，我想將類對象轉換為JSON字符串，我該怎么做？ 我是否必須先將這些對象放入容器（如矢量或列表）中，然后將其寫入JSON？

是的，你將它們放入樹容器中，即boost::property_tree::ptree ：

住在Coliru

#include <boost/property_tree/json_parser.hpp>
#include <boost/property_tree/ptree.hpp>
#include <iostream>
#include <sstream>
using boost::property_tree::ptree;

namespace Entities {

    struct POST1 {
        std::string TokenNo;
        std::string CommandStatus;
        std::string CommandID;
        std::string CPUID;
        std::string ISEncrypted;

    };

    std::string to_json(POST1 const& o) {
        ptree out;
        out.put("POST1.TokenNo",          o.TokenNo);
        out.put("POST1.CommandStatus",    o.CommandStatus);
        out.put("POST1.CommandID",        o.CommandID);
        out.put("POST1.CPUID",            o.CPUID);
        out.put("POST1.ISEncrypted",      o.ISEncrypted);

        std::ostringstream oss;
        boost::property_tree::write_json(oss, out);
        return oss.str();
    }
}

// ADL trigger; `using Entities::to_json` would be roughly equivalent, but not
// make it clear that ADL is happening
void to_json();

int main() {
    Entities::POST1 obj { "1122", "0", "00", "A1234B1234", "0" };
    std::cout << to_json(obj);
}

輸出：

{
    "POST1": {
        "TokenNo": "1122",
        "CommandStatus": "0",
        "CommandID": "00",
        "CPUID": "A1234B1234",
        "ISEncrypted": "0"
    }
}

Answer 2

使用 boost 1.78.0，你可以使用這個

Answer 3

use this simple way

pt::ptree root;


    root.put("POST1 .TokenNo", "1122");
    root.put("POST1 .CommandStatus", "0");
    root.put("POST1 .CommandID", "00");
    root.put("POST1 .CPUID", "A1234B1234");
    root.put("POST1 .ISEncrypted", "0");
    // Once our ptree was constructed, we can generate JSON on standard output

    pt::write_json(std::cout, root);

OUT PUT

{“POST1”：{“TokenNo”：“1122”，“CommandStatus”：“0”，“CommandID”：“00”，“CPUID”：“A1234B1234”，“ISEncrypted”：“0”}}