Use QT to traverse JSON documents and search sub objects

About qt Traverse Json The code of the document , Sort it out and record it here , Convenient for future use .

QT The version of is shown in the figure below

 Json The contents of the document ：

{
  " animal ": {
    " people ": {
      " Age ": 43,
      " Telephone ": [
        "[phone]",
        "[phone]"
      ]
    },

    " Dog ": {
      " leg ": [
        " Left front leg ",
        " Right front leg ",
        " Left hind leg ",
        " Right hind leg "
      ],
      " head ": {
        " eyes ": 2,
        " nose ": 1,
        " Ears ": 2
      }
    }
  }
}

Use QJsonDocument The output of traversing all objects is as follows ：

"" " root " isObject()  Yes   1   Subobject  
"    " " animal " isObject()  Yes   2   Subobject  
"        " " people " isObject()  Yes   2   Subobject  
"            " " Age "  isDouble()  43
"            " " Telephone " isArray()  Yes   2   Subobject  
"                " ""  isString()  "[phone]"
"                " ""  isString()  "[phone]"
"        " " Dog " isObject()  Yes   2   Subobject  
"            " " head " isObject()  Yes   3   Subobject  
"                " " eyes "  isDouble()  2
"                " " Ears "  isDouble()  2
"                " " nose "  isDouble()  1
"            " " leg " isArray()  Yes   4   Subobject  
"                " ""  isString()  " Left front leg "
"                " ""  isString()  " Right front leg "
"                " ""  isString()  " Left hind leg "
"                " ""  isString()  " Right hind leg "

Traverse and output Json Object code ：

    // load Json file     
    static void LoadJsonFromFile(const QString& jsonfilename,QJsonDocument& jsDoc)
    {
        QFile file(jsonfilename);
        file.open(QIODevice::ReadWrite);
        QByteArray json = file.readAll();
        jsDoc = QJsonDocument::fromJson(json);
    }


    // Traverse the output Json object 
    // Input is Json file 
    static void PrintJson(QJsonDocument& jDoc)
    {
        if(jDoc.isObject()) 
        {
            QJsonObject jObject = jDoc.object();  // Get root object 
            PrintJsonObject(jObject," root ");
        }
        else if(jDoc.isArray())
        {
            QJsonArray jArray = jDoc.array();
            PrintJsonArray(jArray,"");
        }
        else
        {
            // empty document 
            qDebug() << " empty document ";
        }
    }

    // Traverse QJsonObject
    static void PrintJsonObject(QJsonObject& obj,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        qDebug() << tabs << key << "isObject()  Yes  " << obj.size() <<  "  Subobject  ";
        for(const QString& key: obj.keys())  // Traverse all key
        {
            QJsonValue jvalue = obj[key];
            PrintJsonValue(jvalue,key,retract+1); // Printout QJsonValue
        }
    }


    // Traverse QJsonArray
    static void PrintJsonArray(QJsonArray& arr,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        qDebug() << tabs << key << "isArray()  Yes  " << arr.size() <<  "  Subobject  ";
        for(QJsonArray::iterator it=arr.begin();it!=arr.end();++it)  // Traverse the objects in the array 
        {
            QJsonValue jvalue = *it;
            PrintJsonValue(jvalue,"",retract+1); // Printout QJsonValue
        }
    }

    // Printout QJsonValue
    static void PrintJsonValue(QJsonValue& jvalue,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        if(jvalue.isArray())
        {
            QJsonArray childArray = jvalue.toArray();
            PrintJsonArray(childArray,key,retract);  // Recursively call 
        }
        else if(jvalue.isObject())
        {
            QJsonObject childObject = jvalue.toObject();
            PrintJsonObject(childObject,key,retract);  // Recursively call 
        }
        else if(jvalue.isBool())
        {
            qDebug() << tabs << key << " isBool() " << jvalue.toBool();
        }
        else if(jvalue.isDouble())
        {
            qDebug() << tabs << key << " isDouble() " << jvalue.toDouble();
        }
        else if(jvalue.isString())
        {
            qDebug() << tabs << key << " isString() " << jvalue.toString();
        }
        else if(jvalue.isUndefined())
        {
            qDebug() << tabs << " isUndefined() ";
        }
        else if(jvalue.isNull())
        {
            qDebug() << tabs << " isNull() ";
        }
    }


    // Test code 
    QJsonDocument doc;                        
    ZJsonTools::LoadJsonFromFile(QString("json Full path name of the file "),doc);
    ZJsonTools::PrintJson(doc);

Search for Json Code for ：

    static bool SearchJsonValue(const QJsonObject& jObject,const QStringList& path,QJsonValue& result)
    {
        QJsonValue jValue = jObject;
        return SearchJsonValue(jValue,path,result);
    }

    static bool SearchJsonValue(const QJsonValue& jValue,const QStringList& path,QJsonValue& result)
    {
        result = jValue;
        for(int i=0;i<path.length();++i)
        {
            result = result[path[i]];
            if(result.isNull() || result.isUndefined())
            {
                return false;
            }
        }
        return true;
    }


    // Test code 
    QStringList path = {" animal "," Dog "," head "," nose "};
    QJsonObject jObject = doc.object();
    QJsonValue jObj;
    if(ZJsonTools::SearchJsonValue(jObject,path,jObj))
    {
        qDebug()<< "  Number of dogs' noses ： " << jObj.toInt();
    }
    else
    {
        qDebug()<< "   Not found  ";
    }

Search for Json Test code output ：

  Number of dogs' noses ：  1

complete ZJsonTools Class code ：

#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonValue>
#include <QJsonArray>
#include <QString>
#include <QFile>
#include <QList>
#include <QDebug>

class ZJsonTools final
{
private:
    ZJsonTools();

public:
    static void LoadJsonFromFile(const QString& jsonfilename,QJsonDocument& jsDoc)
    {
        QFile file(jsonfilename);
        file.open(QIODevice::ReadWrite);
        QByteArray json = file.readAll();
        jsDoc = QJsonDocument::fromJson(json);
    }

    static void PrintJson(QJsonDocument& jDoc)
    {
        if(jDoc.isObject())
        {
            QJsonObject jObject = jDoc.object();
            PrintJsonObject(jObject," root ");
        }
        else if(jDoc.isArray())
        {
            QJsonArray jArray = jDoc.array();
            PrintJsonArray(jArray,"");
        }
        else
        {
            // empty document 
            qDebug() << " empty document ";
        }
    }

    static bool SearchJsonValue(const QJsonObject& jObject,const QStringList& path,QJsonValue& result)
    {
        QJsonValue jValue = jObject;
        return SearchJsonValue(jValue,path,result);
    }

    static bool SearchJsonValue(const QJsonValue& jValue,const QStringList& path,QJsonValue& result)
    {
        result = jValue;
        for(int i=0;i<path.length();++i)
        {
            result = result[path[i]];
            if(result.isNull() || result.isUndefined())
            {
                return false;
            }
        }
        return true;
    }

private:
    static void PrintJsonObject(QJsonObject& obj,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        qDebug() << tabs << key << "isObject()  Yes  " << obj.size() <<  "  Subobject  ";
        for(const QString& key: obj.keys())
        {
            QJsonValue jvalue = obj[key];
            PrintJsonValue(jvalue,key,retract+1);
        }

    }

    static void PrintJsonArray(QJsonArray& arr,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        qDebug() << tabs << key << "isArray()  Yes  " << arr.size() <<  "  Subobject  ";
        for(QJsonArray::iterator it=arr.begin();it!=arr.end();++it)
        {
            QJsonValue jvalue = *it;
            PrintJsonValue(jvalue,"",retract+1);
        }
    }

    static void PrintJsonValue(QJsonValue& jvalue,const QString& key,int retract=0)
    {
        // Indent used for output 
        QString tabs = "";
        for(int i=0;i<retract;++i) {tabs+="    ";}

        if(jvalue.isArray())
        {
            QJsonArray childArray = jvalue.toArray();
            PrintJsonArray(childArray,key,retract);
        }
        else if(jvalue.isObject())
        {
            QJsonObject childObject = jvalue.toObject();
            PrintJsonObject(childObject,key,retract);
        }
        else if(jvalue.isBool())
        {
            qDebug() << tabs << key << " isBool() " << jvalue.toBool();
        }
        else if(jvalue.isDouble())
        {
            qDebug() << tabs << key << " isDouble() " << jvalue.toDouble();
        }
        else if(jvalue.isString())
        {
            qDebug() << tabs << key << " isString() " << jvalue.toString();
        }
        else if(jvalue.isUndefined())
        {
            qDebug() << tabs << " isUndefined() ";
        }
        else if(jvalue.isNull())
        {
            qDebug() << tabs << " isNull() ";
        }
    }

};