QT JSON string generation and parsing

1 qt JSON string generation and parsing 1.1 qt JSON parsing process

(1) the string is converted to qjsondocument

Qjsonparseerror Json_error;

Qjsondocument Json_doc = Qjsondocument::fromjson (Lpc_body.c_str (), &json_error);

if (json_error.error! = qjsonparseerror::noerror)

{

Logic_error ("Parse json ERROR%d", json_error.error);

return false;

( 2 ) qjsondocument translates to Qjsonobject

Qjsonobject json_object = Json_doc.object ();

( 3 ) by Qjsonobject function to get the value

Qjsonobject json_object = Json_doc.object ();

if (!json_object.contains ("Data"))

{

Logic_info ("RECV server subscribeevent return data%s", Data.lpc_body. C_str());

return true;

}

Qjsonobject qdata= json_object["Data"].toobject ();

if (! Qdata.contains ("message"))

{

Logic_error ("Json_object can ' t find Message");

return false;

}

Qjsonobject message = qdata["message"].toobject ();

Next is the data field

if (! Message.contains ("EventData"))

{

Logic_error ("Can ' t find EventData");

return false;

}

Qjsonobject EventData = message["EventData"].toobject ();

if (! Eventdata.contains ("Alarmmessage"))

{

Logic_error ("Can ' t find Alarmmessage");

return false;

}

Qjsonobject alarmmsg = eventdata["Alarmmessage"].toobject ();

Alarmdata.stralarmname = alarmmsg["Objectivename"].tostring (). tostdstring ();

Alarmdata.strstime = alarmmsg["AlarmTime"].tostring ();

Alarmdata.streventid = alarmmsg["EventId"].tostring (). tostdstring ();

Alarmdata.stralarmlevel = alarmmsg["Eventlevel"].tostring (). tostdstring ();

Alarmdata.streventtype = alarmmsg["EventType"].tostring (). tostdstring ();

Alarmdata.stralarmlogid = alarmmsg["id"].tostring (). tostdstring ();

Logic_info ("Parase Alarm success!");

1.2 QT JSON construction process

The construction process is the opposite of the parsing process

(1) Create a Qjsonobject object and insert the various types of values through the Insert function.

Iterator Insert (const QString &key, const qjsonvalue &value);

Where Qjsonvalue is a class with multiple constructors, you can enter multiple data types. You can use various functions to determine and convert to the corresponding data type.

constructor function

Qjsonvalue (Type = Null);

Qjsonvalue (bool b);

Qjsonvalue (double n);

Qjsonvalue (int n);

Qjsonvalue (qint64 N);

Qjsonvalue (const QString &s);

Qjsonvalue (qlatin1string s);

Type judgment function

Type type () const;

inline bool IsNull () const {return type () = = Null;}

inline bool Isbool () const {return type () = = bool;}

inline bool Isdouble () const {return type () = = Double;}

inline bool Isstring () const {return type () = = String;}

inline bool IsArray () const {return type () = = Array;}

inline bool IsObject () const {return type () = = Object;}

inline bool isundefined () const {return type () = = Undefined;}

Convert output function

BOOL Tobool (BOOL DefaultValue = false) const;

int toint (int defaultvalue = 0) const;

Double ToDouble (Double defaultvalue = 0) const;

QString toString () const;

QString toString (const QString &defaultvalue) const;

Qjsonarray ToArray () const;

Qjsonarray ToArray (const qjsonarray &defaultvalue) const;

Qjsonobject toobject () const;

Qjsonobject toobject (const qjsonobject &defaultvalue) const;

Qjsonobject Json_object;

Json_object.insert ("ErrorCode", 1);//number

Json_object.insert ("Errormodule", "error_module");//String

Json_object.insert ("bool", true);

You can directly convert the corresponding data in the map to a JSON string

if (!key_value. Empty())

{

Json_object.insert ("Data", Qjsonobject::fromvariantmap (Key_value));

}

( 2 ) After organizing the structure, use qjsondocument of the SetObject function Settings Object

Qjsondocument Json_doc;

Json_doc.setobject (Json_object);

( 3 ) with qjsondocument of the Tojson function into a string

String str= Json_doc.tojson (qjsondocument::compact);

Qjson character parsing and generation This is the case, if you want to get a deeper understanding. You can go to the constructor to learn more about the interface.

QT JSON string generation and parsing