Why shows error message when generating application release

[SGaist]

@lincoln said in Why shows error message when generating application release:

QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

You are still creating multiple QSqlDatabase objects using the default connection. One might be wrong.

[lincoln]

@SGaist I changed the code in this way, but now it does not connect to the database, I think it is worse.

DbConection class

#ifndef DBCONECTION_H
#define DBCONECTION_H
#include <QSqlDatabase>
#include <QSqlError>

class DbConection
{
public:
  DbConection();
  bool connect(const QString &dbName);
  QString errorMessage(){return _errorMessage;}
  QSqlDatabase getDataBase();
//  void removeDb();


private:
  QString _errorMessage;
  QString mdbName;

};

#endif // DBCONECTION_H

#include "dbconection.h"


DbConection::DbConection(){

}

bool DbConection::connect(const QString &dbName)
{
  mdbName=dbName;
  auto db=QSqlDatabase::addDatabase("QPSQL",dbName);
  if(!db.isDriverAvailable("QPSQL")){
      _errorMessage=db.lastError().driverText();
      return false;
    }
  db.setDatabaseName("monitoreo_db");
  db.setPort(5432);
  db.setHostName("127.0.0.1");
  db.setUserName("postgres");
  db.setPassword("2311046");

  if(!db.open()){
      _errorMessage=db.lastError().databaseText();
      return false;
    }

  return true;

}

QSqlDatabase DbConection::getDataBase()
{

  return QSqlDatabase::database(mdbName);

}

BussinesLayer class:

#ifndef BUSSINESLAYER_H
#define BUSSINESLAYER_H

#include <QSqlQuery>
#include <QSqlError>
#include "dbconection.h"

class BussinesLayer : public QObject
{

public:
  BussinesLayer();  
  QVariantList selectData(QVariant id);
  
private:
  QString _errorMessage;
  QString _errorCode;  
  DbConection db;
  
};

#endif // BUSSINESLAYER_H


#include "bussineslayer.h"

BussinesLayer::BussinesLayer()
{

  db.connect("monitoreo");

}

QVariantList BussinesLayer::selectData(QVariant id)
{
  QVariantList dataList;
  QSqlQuery qry(db.getDataBase());
  qry.prepare("SELECT * FROM grupo_minero WHERE id=?");
  qry.addBindValue(id);
  if(!qry.exec()){
    _errorMessage=qry.lastError().text();
    return dataList;
}        
  return dataList;

}

now this message comes out

😟😠

[jsulm]

@lincoln said in Why shows error message when generating application release:

DbConection::connect(const QString &dbName)

^Where do you call it now in your code? You need to call it once before using the database connection.

[JonB]

@jsulm
He calls it in the BussinesLayer::BussinesLayer() constructor: db.connect("monitoreo");.

@lincoln
In DbConection::connect() you check for db.isDriverAvailable("QPSQL") after you have called QSqlDatabase::addDatabase(). I suggest you want to call it before.

On error you set _errorMessage and return false, yet you don't check for that nor show the error message.

Your console output still shows "duplicate connection", which implies you are still calling DbConection::connect() more than once. Since you call it from BussinesLayer constructor, maybe your outside world code creates a BussinesLayer more than once.

Can you please put in your own qDebug() messages to see what is getting executed in your own code, and for your error messages. This is a standard part of programming. For example, put one in at the start of DbConection::connect(). If that gets printed out more than once, you are in trouble....

[lincoln]

@JonB a business layer, I call it from several forms, in the private part of the .h file of each form, I declare a variable of type bussineslayer class, in that class I have all the code I need to be able to do the DB tasks.

here for example in "mainwindow.h"

and so on all the forms you need from the bussineslayer class.

Use a QMessageBox, to display the message and this is what it displays

I don't understand, when I don't pass the name of the connection in QSqlDatabase :: addDatabase ("QPSQL", dbName);
data is displayed normally.

[JonB]

@lincoln
Please copy & paste code rather than a screenshot. Same for error messages. It makes life easier for everyone.

You have written code to create a new database connection, unconditionally, in BussinesLayer's constructor. If you have multiple BussinesLayer instances you will be creating multiple, duplicate connections. As per the error message you showed you get.

You don't want that, do you? Multiple connections to the database? So you had better change code not to do that. Why do you have multiple BussinesLayer' instances anyway?

[lincoln]

@JonB

Ok, I saw what my error is, I was not passing the name of the connection when creating my QsqlQuery.
now if it shows the data without problems. so I remain.

class for connection to DB:

#ifndef DBCONECTION_H
#define DBCONECTION_H
#include <QSqlDatabase>
#include <QSqlError>
#include <QObject>


class DbConection: public QObject
{
public:
  explicit DbConection(QObject *parent=nullptr);
  bool connect(const QString &dbName);
  QString errorMessage(){return _errorMessage;}
  QSqlDatabase getDataBase();
//  void removeDb();

private:
  QString _errorMessage;
  QString mdbName;

};

#endif // DBCONECTION_H

#include "dbconection.h"
#include <QDebug>

DbConection::DbConection(QObject *parent):
  QObject(parent)
{

}

bool DbConection::connect(const QString &dbName)
{
  mdbName=dbName;
  //  auto db=QSqlDatabase::addDatabase("QPSQL",dbName);
  QSqlDatabase db;
  if(!db.isDriverAvailable("QPSQL")){
      _errorMessage=db.lastError().driverText();
//      qDebug()<<_errorMessage;
      return false;
    }
  db=QSqlDatabase::addDatabase("QPSQL",dbName);
  db.setPort(5432);
  db.setHostName("127.0.0.1");
  db.setDatabaseName("monitoreo_db");
  db.setUserName("postgres");
  db.setPassword("2311046");

  if(!db.open()){
      _errorMessage=db.lastError().databaseText();
//      qDebug()<<_errorMessage;
      return false;
    }

  return true;

}

QSqlDatabase DbConection::getDataBase()
{

  return QSqlDatabase::database(mdbName);

}

BussinesLayer class:

#ifndef BUSSINESLAYER_H
#define BUSSINESLAYER_H

#include <QSqlQuery>
#include <QSqlError>
#include "dbconection.h"

class BussinesLayer : public QObject
{

public:
  explicit BussinesLayer(QObject *parent=nullptr);
  QHash<int, QString> selectDataClient();
  
private:
  QString _errorMessage;
  QString _errorCode;  
  DbConection db;
  
};

#endif // BUSSINESLAYER_H

#include "bussineslayer.h"
#include <QDebug>
BussinesLayer::BussinesLayer(QObject *parent):
  QObject(parent)
{

  if(!db.connect("monitoreo"))
    qDebug()<<db.errorMessage();

}

QHash<int, QString> BussinesLayer::selectDataClient()
{
  QHash<int,QString> dataList;

  QSqlQuery qry(db.getDataBase());
  qry.prepare("SELECT id,nombre_unidad FROM cliente");

  if(!qry.exec()){
      _errorMessage=qry.lastError().text();
       return dataList;
    }
  while(qry.next()){
      dataList.insert(qry.value(0).toInt(),qry.value(1).toString());
    }
  return dataList;
}

And this in the mainwindow:

private:
  Ui::MainWindow *ui;
  BussinesLayer bLayer;

void MainWindow::loadData()
{
  QHash<int,QString> dataList;
  dataList=bLayer.selectDataClient();
  if(dataList.isEmpty()){
      QMessageBox::critical(this,qApp->applicationName(),bLayer.errorMessage());
      return;
    }
  ui->cboGrupo->addItems(dataList.values());  

}

But still the duplicate connection message persists, as I mentioned above, I have to create a new variable of type BussinesLayer in the other forms, in order to have access to the other data that I use in the other forms.

[SGaist]

Because if you have several BusinessLayer objects, they will all use the same named connection the way you implemented it.

[lincoln]

@SGaist said in Why shows error message when generating application release:

Because if you have several BusinessLayer objects, they will all use the same named connection the way you implemented it.

Well, I was also able to solve the issue of generating the release, now the data is displayed correctly, what remains in doubt is, how do I access the functionality of my BussinesLayer class in the other forms, without that annoying message of duplicate connection.

😒 🥴

[SGaist]

Currently you are using the same connection everywhere thus as we already suggested several times: do the initialisation once and be done with it.

The other solution is to create a different named connection for each instance of BusinessLayer.

[lincoln]

@SGaist said in Why shows error message when generating application release:

Currently you are using the same connection everywhere thus as we already suggested several times: do the initialisation once and be done with it.
The other solution is to create a different named connection for each instance of BusinessLayer.

ok thanks