/*

 * Copyright (c) 2007-2008 Nokia Corporation and/or its subsidiary(-ies).

 * All rights reserved.

 * This component and the accompanying materials are made available

 * under the terms of the License "Eclipse Public License v1.0"

 * which accompanies this distribution, and is available

 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

 *

 * Initial Contributors:

 * Nokia Corporation - initial contribution.

 *

 * Contributors:

 *

 * Description:  

 *

 */

package com.nokia.helium.metadata;

import javax.persistence.EntityManager;

import javax.persistence.EntityManagerFactory;

/**

 * This class implements a simplified EntityManager

 * designed for batch committing.

 * Serial persists are committed and cleared each time

 * the limit is reached.  

 *

 */

public class AutoCommitEntityManager {

    private EntityManager entityManager;

    private int count;

    private int maxCount = 750;

    /**

     * Creating a new AutoCommitEntityManager. The entityManagerFactory will be 

     * used to get a new EntityManager.

     * @param entityManagerFactory the entity manager to use to create a EntityManager.

     */

    public AutoCommitEntityManager(EntityManagerFactory entityManagerFactory) {

        this.entityManager = entityManagerFactory.createEntityManager();

        entityManager.getTransaction().begin();

    }

    /**

     * Persisting an object into the database.

     * @param o the object to persist

     */

    public synchronized void persist(Object o) {

        entityManager.persist(o);

        count++;

        if (count >= maxCount) {

            entityManager.getTransaction().commit();

            entityManager.clear();

            count = 0;

            entityManager.getTransaction().begin();

        }

    }

    /**

     * Closing the current entity manager. Committing any 

     * pending operation.

     */

    public synchronized void close() {

        if (entityManager.getTransaction().isActive()) {

            entityManager.getTransaction().commit();

            entityManager.clear();

        }

        entityManager.close();

        entityManager = null;

    }

    /**

     * Internal EntityManager used to

     * @param <T>

     * @return the merged entity.

     */

    public <T> T merge(T entity) {

        return entityManager.merge(entity);

    }

}