How to release Connection in Hibernate?

Question

Java

Hello, after several requests in the application, I came across such an exception

java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30002ms.

I didn’t set up a connection pool, my task was to use the usual Hibernate in the Spring application, for this I took out the Session from the EntityManager every time and worked with it, as is done in the usual hibernate. As far as I understand, the dataSource is responsible for the connection pool, and this thing is already in the JDBC part. How can I not overflow the connection pool in my application or release it using Hibernate tools?
My Dao implementations look something like this:

@Component
public class GrowBoxDaoImpl implements GrowBoxDao {

    @Autowired
    private EntityManagerFactory entityManagerFactory;

    @Override
    public List<GrowBox> findByUser(Long userId) {

        Session session = entityManagerFactory.unwrap(SessionFactory.class).openSession();
        String hqlQuery = "from GrowBox gb where gb.responsibleUser.id =: userId";
        Query query = session.createQuery(hqlQuery);
        query.setParameter("userId", userId);
        List growBoxes = query.getResultList();
        session.close();
        return growBoxes;
    }

    @Override
    public GrowBox findById(Long id) {

        Session session = entityManagerFactory.unwrap(SessionFactory.class).openSession();
        GrowBox growBox = session.get(GrowBox.class, id);
        session.close();

        return growBox;
    }

    @Override
    public GrowBox saveBox(GrowBox box) {
        Session session = entityManagerFactory.unwrap(SessionFactory.class).openSession();
        session.getTransaction().begin();
        session.saveOrUpdate(box);
        session.flush();
        session.getTransaction().commit(); // call flush too
        session.close();
        return box;
    }

    @Override
    public void deleteBox(Long id) {

        String hqlQuery = "delete GrowBox where id =: id";
        Session session = entityManagerFactory.unwrap(SessionFactory.class).openSession();
        session.getTransaction().begin();

        session.createQuery(hqlQuery).setParameter("id", id).executeUpdate();
        session.flush();
        session.getTransaction().commit();
        session.close();
    }
}

I have several entities, each has its own Dao and its own Service, several controllers in which these Services are used
in my Dao I tried to correctly execute transactions and always closed sessions
here is the full project repository if it helps https://github.com/DennisKingsman/ HibernateWithSpr...
PS disconnect() method; doesn't help either

Answer 1

I will assume that the problem is not in the hibernate, but in the transaction manager. transactions are opened but not closed. session from hibernate has nothing to do with it.
I would advise:
a) to define explicit boundaries of transactions
b) to debug who opens and why does not pop up in the closing (commit or rollback) of the transaction