qt 如何连接mysql数据库连接池

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QSqlError>
#include <QDebug>

void initConnectionPool() {
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("testdb");
    db.setUserName("root");
    db.setPassword("password");

    if (!db.open()) {
        qDebug() << "Error: connection with database failed";
        return;
    }

    // 创建多个连接
    for (int i = 0; i < 10; ++i) {
        QSqlDatabase::addDatabase("QMYSQL", QString("connection_%1").arg(i));
    }
}

QSqlDatabase getConnectionFromPool() {
    for (int i = 0; i < 10; ++i) {
        QSqlDatabase db = QSqlDatabase::database(QString("connection_%1").arg(i));
        if (db.isOpen() && !db.transactionActive()) {
            return db;
        }
    }
    return QSqlDatabase();
}

void releaseConnectionToPool(QSqlDatabase db) {
    db.close();
}

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);

    initConnectionPool();

    QSqlDatabase db = getConnectionFromPool();
    if (db.isOpen()) {
        QSqlQuery query(db);
        query.exec("SELECT * FROM testtable");
        while (query.next()) {
            qDebug() << query.value(0).toString();
        }
        releaseConnectionToPool(db);
    }

    return a.exec();
}