/*

 * 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 java.io.Serializable;

import java.lang.reflect.ParameterizedType;

import java.util.List;

import javax.persistence.EntityManager;

import javax.persistence.PersistenceContext;

/**

 * Abstract class which implement the DAO pattern for the JPA

 * API. 

 *

 * @param <T> implementing the DAO for T.

 */

public abstract class JpaDAO<T> implements DAO<T> {

    private Class<T> entityBeanType;

    @PersistenceContext

    private EntityManager entityManager;

    /**

     * Default constructor. Does some basic internal configuration.

     */

    @SuppressWarnings("unchecked")

    public JpaDAO() {

        this.entityBeanType = (Class<T>) ((ParameterizedType) getClass()

                .getGenericSuperclass()).getActualTypeArguments()[0];

    }

    /**

     * @param entityManager the entityManager to set

     */

    public void setEntityManager(EntityManager entityManager) {

        this.entityManager = entityManager;

    }

    /**

     * @return the entityManager

     */

    protected EntityManager getEntityManager() {

        return entityManager;

    }

    /**

     * {@inheritDoc}

     */

    public T findById(Serializable id) {

        return entityManager.find(getEntityBeanType(), id);

    }

    /**

     * {@inheritDoc}

     */

    public List<T> findAll() {

        return entityManager.createQuery("from " +

                getEntityBeanType().getName(), getEntityBeanType()).getResultList();

    }

    /**

     * Get the class this object is implementing the DAO for.  

     * @return the class this object is implementing the DAO for.

     */

    protected Class<T> getEntityBeanType() {

        return entityBeanType;

    }

    /**

     * {@inheritDoc}

     */

    public void persist(T data) {

        entityManager.persist(data);

    }

    /**

     * {@inheritDoc}

     */

    public void remove(T data) {

        entityManager.remove(data);

    }

}