Problems with QtSqlDatabase and threads

[rileo8]

Hi, i have an application that use threads and (if possible) a Sqlite database.
the main is this one:

@int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.showMaximized();

QMutex *configurationMutex=new QMutex();
Configuration *configuration=new Configuration();

Checker checker(0,configuration,configurationMutex);
Networker networker(0,configuration,configurationMutex);
Executer executer(0,configuration,configurationMutex);

QThread checkerThread;
QThread networkerThread;
QThread executerThread;

QObject::connect(&executerThread,SIGNAL(started()),&executer,SLOT(Start()));
QObject::connect(&w,SIGNAL(SignalTest()),&checker,SLOT(TestSlot()));

checker.moveToThread(&checkerThread);
networker.moveToThread(&networkerThread);
executer.moveToThread(&executerThread);

file_name();

checkerThread.start();
networkerThread.start();
executerThread.start();

int returnValue=a.exec();

executerThread.wait();

return returnValue;

}@

in the executer thread start function i have this:

@QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("testDB.db3");
if(db.open())
{
qDebug()<<"Database opened";
db.close();
}
else
{
qDebug()<<"Problem opening database "<<db.lastError().text();
}@

but driver load failed and it gives me those errors:

@
QCoreApplication::applicationDirPath: Please instantiate the QApplication object first
SqlDatabase: QSQLITE driver not loaded
QSqlDatabase: available drivers:
QSqlDatabase: an instance of QCoreApplication is required for loading driver plugins
@

i think is because i start the executer thread before calling a.exec()..
How can i solve this?

thanks,
Riccardo