JpaDAO.java

package com.retailwave.fce.server.dao;

/**
 * $Id: JpaDAO.java 5 2010-06-03 11:07:35Z muthu $
 * $HeadURL: svn://10.10.200.111:3691/Finance/tags/framework-snapshot1/fce/src/main/java/com/retailwave/fce/server/dao/JpaDAO.java $
 */

import org.springframework.orm.jpa.JpaCallback;
import org.springframework.orm.jpa.support.JpaDaoSupport;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceException;
import javax.persistence.Query;
import java.lang.reflect.ParameterizedType;
import java.util.List;

public abstract class JpaDAO<K, E> extends JpaDaoSupport {

    protected Class<E> entityClass;

    @SuppressWarnings("unchecked")
    public JpaDAO() {
        ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();
        this.entityClass = (Class<E>) genericSuperclass.getActualTypeArguments()[1];
    }

    public void persist(E entity) {
        getJpaTemplate().persist(entity);
    }

    public void remove(E entity) {
        getJpaTemplate().remove(entity);
    }

    public E merge(E entity) {
        return getJpaTemplate().merge(entity);
    }

    public void refresh(E entity) {
        getJpaTemplate().refresh(entity);
    }

    public E findById(K id) {
        return getJpaTemplate().find(entityClass, id);
    }

    public E flush(E entity) {
        getJpaTemplate().flush();
        return entity;
    }

    @SuppressWarnings("unchecked")
    public List<E> findAll() {
        Object res = getJpaTemplate().execute(new JpaCallback() {

            public Object doInJpa(EntityManager em) throws PersistenceException {
                Query q = em.createQuery("SELECT h FROM " +
                        entityClass.getName() + " h");
                return q.getResultList();
            }

        });

        return (List<E>) res;
    }

    @SuppressWarnings("unchecked")
    public Integer removeAll() {
        return (Integer) getJpaTemplate().execute(new JpaCallback() {

            public Object doInJpa(EntityManager em) throws PersistenceException {
                Query q = em.createQuery("DELETE FROM " +
                        entityClass.getName() + " h");
                return q.executeUpdate();
            }

        });
    }

}