Question

I’ve been reading about the sun blueprint GenericDAO implementation and Gavin King’s take on this for use with Hibernate. It seems he doesn’t mention anything about transaction handling:

public abstract class GenericHibernateDAO<T, ID extends Serializable> {
    protected Session getSession() {
        return HibernateUtil.getSessionFactory().getCurrentSession();
    }

    public T makePersistent(T entity) {
        getSession().saveOrUpdate(entity);
        return entity;
    }
}

I’m puzzled as to where I should put the start/end of the transaction. Currently they are inside the DAOs that extend this GenericHibernateDAO

public class FooHibernateDAO extends GenericHibernateDAO<Foo, Long> {
    public Foo saveFoo(Foo foo) {
        getSession().beginTransaction();
        makePersistent(foo);
        getSession().getTransaction().commit();
    }
}

Should the transaction handling be managed by the caller of the DAO in the application tier?

Answer 1

Generally the best practice is to manage transactions in service layer not in DAO layer. Each DAO method generally handles one specific operation and a service method aggregates them in one transaction.