问题
I am fairly new to C++ and I apologise beforehand if you find this very easy.
I have the following files 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
Below is 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);
}
NOTE:-
(1) sqliteDB is another class declared in a .cpp file.
(2) the output of function dump() is a json string. this get stored into JSON_Cmnd_string.
So, I want to convert the class object into JSON string, How can I do that ? Do I have to first put these object into a container (like vector or list) and then write it into JSON?
回答1:
This is not "fairly easy", because C++ doesn't have JSON support.
Neither does Boost:
- how to get boost json to use the correct data types
That said, this appears to be what you want:
- http://www.boost.org/doc/libs/1_57_0/doc/html/boost_propertytree/tutorial.html
So, I want to convert the class object into JSON string, How can I do that ? Do I have to first put these object into a container (like vector or list) and then write it into JSON?
Yes, you put them into a tree container, namely boost::property_tree::ptree
:
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#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);
}
Output:
{
"POST1": {
"TokenNo": "1122",
"CommandStatus": "0",
"CommandID": "00",
"CPUID": "A1234B1234",
"ISEncrypted": "0"
}
}
回答2:
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" } }
来源:https://stackoverflow.com/questions/29363347/how-to-convert-class-object-to-json-string-using-boost-library-in-c