/**

  * Copyright 2010 The Kuali Foundation Licensed under the

  * Educational Community License, Version 2.0 (the "License"); you may

  * not use this file except in compliance with the License. You may

  * obtain a copy of the License at

  *

  * http://www.osedu.org/licenses/ECL-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an "AS IS"

  * BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

  * or implied. See the License for the specific language governing

  * permissions and limitations under the License.

  */

 package org.kuali.student.core.dao.impl;

 import java.util.List;

 import javax.persistence.EntityManager;

 import javax.persistence.Query;

 import org.kuali.student.core.dao.CrudDao;

 import org.kuali.student.core.exceptions.DoesNotExistException;

 public abstract class AbstractCrudDaoImpl implements CrudDao {

         protected EntityManager em;

         public EntityManager getEm() {

                 return em;

         }

         public void setEm(EntityManager em) {

                 this.em = em;

         }

         @Override

         public <T> T fetch(Class<T> clazz, String key) throws DoesNotExistException {

                 T entity = em.find(clazz, key);

                 if (entity == null) {

                         throw new DoesNotExistException("No entity for key '" + key + "' found for " + clazz);

                 }

                 return entity;

         }

         @SuppressWarnings("unchecked")

         @Override

         public <T> List<T> find(Class<T> clazz){

                 String className = clazz.getSimpleName();

                 Query q = em.createQuery("SELECT x FROM "+className+" x");

                 return (List<T>) q.getResultList();

         }

         @Override

         public <T> T create(T entity) {

                 em.persist(entity);

                 return entity;

         }

         @Override

         public <T> void delete(Class<T> clazz, String key) throws DoesNotExistException {

                 T entity = em.find(clazz, key);

                 if (entity == null) {

                         throw new DoesNotExistException("No such key '" + key + "' for " + clazz);

                 }

                 em.remove(entity);

         }

         @Override

         public void delete(Object entity) {

                 em.remove(entity);

         }

         @Override

         public <T> T update(T entity) {

                 T updated =  em.merge(entity);

                 //We need to flush here to make sure the version number is updated before we populate any messages that return the version

                 em.flush();

                 return updated;

         }

 }