JPA EntityManager doesn't get closed while GCing (Performance issue)

Question

We have been using annotation based JPA with Hibernate as JpaVendorAdapter. We had to schedule a job to refresh an entire table data using spring scheduler. The code is as follows,

@Scheduled(fixedDelay=120000)
public void refreshTable() {

    EntityManager em = null;
    try {

        EntityManagerFactory emf = entityManager.getEntityManagerFactory();
        em = emf.createEntityManager();

        em.getTransaction().begin();

        /// do something like delete and fill table
        // this block is done for the sake of batch mode operation

        em.getTransaction().commit();

    } catch (Exception e) {
        logger.error("Failed to refresh table", e);
    } finally{
        if(em != null && em.getTransaction().isActive()){
            em.getTransaction().rollback();
            logger.info("Failure while refreshing table, rolling back transaction.");
        }
    }
}

This used to build memory utilization and caused application hang.

We added, at the end of finally block,

if(em != null){
   em.close();
}

Which solved the memory problem.

So, why does not EntityManager execute close() while being GC'ed?

Answer 1

The JPAConnector has various connections associated with it and it does not close all of them whereas waiting for garbage collector to do it is not a wise approach.

Closing the connections(i.e EntityManager and EntityManagerFactory) as and when they are no more needed is the best way to address this issue.

Hope this helps! Good luck!