JpaTarget.java

package com.seovic.loader.target;


import com.seovic.core.Defaults;
import com.seovic.core.Updater;
import com.seovic.loader.Target;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;


/**
 * A {@link Target} implementation that loads objects into database using JPA.
 *
 * @author Ivan Cikic  2009.11.26
 */
public class JpaTarget
        extends AbstractObjectTarget {

    // ---- constructors ----------------------------------------------------

    /**
     * Construct JpaTarget instance.
     *
     * @param persistenceUnitName the name of persistence unit
     * @param entityClass         the entity class
     */
    public JpaTarget(String persistenceUnitName, Class entityClass) {
        super(entityClass);
        m_persistenceUnitName = persistenceUnitName;
    }


    // ---- Target implementation -------------------------------------------

    /**
     * {@inheritDoc}
     */
    @Override
    public void beginImport() {
        if (m_emf == null) {
            m_emf = Persistence.createEntityManagerFactory(m_persistenceUnitName);
        }
        m_em = m_emf.createEntityManager();
        m_batch = new ArrayList(m_batchSize);
    }

    /**
     * @param item item to import
     */
    @SuppressWarnings({"unchecked"})
    public void importItem(Object item) {
        m_batch.add(item);
        if (m_batch.size() % m_batchSize == 0) {
            mergeInTransaction(m_em, m_batch);
            m_batch.clear();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void endImport() {
        if (!m_batch.isEmpty()) {
            mergeInTransaction(m_em, m_batch);
        }
        if (m_em != null && m_em.isOpen()) {
            m_em.close();
        }
        if (m_emf != null) {
            m_emf.close();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected Updater createDefaultUpdater(String propertyName) {
        return Defaults.createUpdater(propertyName);
    }


    // ---- helper methods --------------------------------------------------


    /**
     * Persist collection of objects.
     *
     * @param em      entity manager used to persist objects
     * @param objects objects to persist
     */
    private void mergeInTransaction(EntityManager em, Collection objects) {
        EntityTransaction tx = null;
        try {
            tx = em.getTransaction();
            tx.begin();
            for (Object o : objects) {
                em.merge(o);
            }
            tx.commit();
        }
        catch (RuntimeException e) {
            if (tx != null && tx.isActive()) {
                tx.rollback();
            }
            throw e;
        }
    }


    // ---- data members ----------------------------------------------------

    /**
     * Default batch size.
     */
    private static final int DEFAULT_BATCH_SIZE = 1000;

    /**
     * The batch size.
     */
    private int m_batchSize = DEFAULT_BATCH_SIZE;

    /**
     * Batch of items.
     */
    private transient List m_batch;

    /**
     * Entity manager factory.
     */
    private EntityManagerFactory m_emf;

    /**
     * Entity manger.
     */
    private EntityManager m_em;

    /**
     * The name of persistence unit.
     */
    private String m_persistenceUnitName;
}