[Qt][QMYSQL] Deployed app - Driver not loaded - mysql

Question

First of all, many thanks for those who will take time to help me on this topic. I've searched a lot on many different forums before posting here but it seems I'm missing something.
Well, I'm working on Windows 7 (64 bits) with Qt5.5 / MySQL Server 5.6.
And I use MinGW 5.5.0 32 bits on Qt Creator (auto detected).
It's not a matter of building the drivers, it's done and it works perfectly for the dev.! :-)
I can reach my BD, do any query that I want and retrieve/insert all the data.
I'm facing to a matter of deploying my application on other computers.
I know that I have to put qsqlmysql.dll in a folder "sqldrivers" placed in my app. directory. Such as placing libmysql.dll in this directory too.
So I have something like the following
App directory
App.exe
libmysql.dll
Qt5Core.dll
Qt5Gui
Qt5Sql
Qt5Widget
libwinpthread-1.dll
libstdc++-6.dll
libgcc_s_dw2-1.dll
platforms
qwindow.dll
sqldrivers
qsqlmysql.dll
BUT when I release the application and I try to run it from another computer which I used to develop, I have a "Driver not loaded" error...
As far now, I have really no idea what I've missed...
So please, if anyone could give me some, it would be really really appreciated!
I let you the part of the code which is really useful, just in case...
main.cpp
QApplication a(argc, argv);
Maintenance w;
w.show();
return a.exec();
Maintenance.cpp
void Maintenance::login(){
int db_select = 1;
this->maint_db = Database(db_select);
/* All that follow is linked to the login of user... */
}
Database.cpp
Database::Database(int default_db)
{
this->db = QSqlDatabase::addDatabase("QMYSQL");
switch(default_db){
case 0:
this->db.setHostName("XXX.XX.XXX.XX");
this->db.setDatabaseName("maintenance_db");
this->db.setUserName("USERNAME");
this->db.setPassword("PASSWORD");
this->db.setPort(3306);
break;
// Only to make some trials in local
case 1:
this->db.setHostName("127.0.0.1");
this->db.setDatabaseName("maintenance_db");
this->db.setUserName("USERNAME");
this->db.setPassword("PASSWORD");
break;
}
/* I've added the following code to try to solve the problem
I retrieve that the available drivers are: QMYSQL / QMYSQL3
But all the information about the DB are empty (due to the unloaded driver I assume.)
And the error from *lastError()* is "Driver not loaded"
*/
QString my_drivers;
for(int i = 0; i < QSqlDatabase::drivers().length(); i++){
my_drivers = my_drivers + " / " + QSqlDatabase::drivers().at(i);
}
QString lib_path;
for(int i = 0; i < QApplication::libraryPaths().length(); i++){
lib_path = lib_path + " / " + QApplication::libraryPaths().at(i);
}
QString start = QString::number(QCoreApplication::startingUp());
QMessageBox::information(0, "BDD init",
"Drivers available: " + my_drivers
+ " \nHostname: " + this->db.hostName()
+ "\nDB name: " + this->db.databaseName()
+ "\nUsername: " + this->db.userName()
+ "\nPW: " + this->db.password()
+ "\n\n" + lib_path + "\n" + start
);
if(this->db.isOpen()){
QMessageBox::information(0, "BDD init", "Already open.");
}
else{
if(this->db.open()){
QMessageBox::information(0, "BDD init", "Opened.");
}
else{
QMessageBox::critical(0, "BDD init", "Not opened.\n" + this->db.lastError().text());
}
}
}

Answer 1

There are at least 3 possible solutions:
Find all .dll paths are correct with your favourite process monitor
Make sure all .dll is in the same arch as your .exe, which is x86 (32bit)
Debug with QPluginLoader

Answer 2

Simplest way to create "deploy" folder for you windows Qt5 aplication is using windeployqt tool
Create empty directory, copy your app.exe file and than run windeployqt app.exe
Check out the docs http://doc.qt.io/qt-5/windows-deployment.html#the-windows-deployment-tool