/*
* Copyright 2006-2013 the original author or authors.
*
* Licensed under the Apache 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.apache.org/licenses/LICENSE-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.springframework.batch.item.database;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.item.ItemWriter;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.orm.jpa.EntityManagerFactoryUtils;
import org.springframework.util.Assert;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import java.util.List;
/**
* {@link org.springframework.batch.item.ItemWriter} that is using a JPA
* EntityManagerFactory to merge any Entities that aren't part of the
* persistence context.
*
* It is required that {@link #write(List)} is called inside a transaction.<br>
*
* The reader must be configured with an
* {@link javax.persistence.EntityManagerFactory} that is capable of
* participating in Spring managed transactions.
*
* The writer is thread-safe after its properties are set (normal singleton
* behaviour), so it can be used to write in multiple concurrent transactions.
*
* @author Thomas Risberg
*
*/
public class JpaItemWriter<T> implements ItemWriter<T>, InitializingBean {
protected static final Log logger = LogFactory.getLog(JpaItemWriter.class);
private EntityManagerFactory entityManagerFactory;
/**
* Set the EntityManager to be used internally.
*
* @param entityManagerFactory the entityManagerFactory to set
*/
public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
this.entityManagerFactory = entityManagerFactory;
}
/**
* Check mandatory properties - there must be an entityManagerFactory.
*/
@Override
public void afterPropertiesSet() throws Exception {
Assert.notNull(entityManagerFactory, "An EntityManagerFactory is required");
}
/**
* Merge all provided items that aren't already in the persistence context
* and then flush the entity manager.
*
* @see org.springframework.batch.item.ItemWriter#write(java.util.List)
*/
@Override
public void write(List<? extends T> items) {
EntityManager entityManager = EntityManagerFactoryUtils.getTransactionalEntityManager(entityManagerFactory);
if (entityManager == null) {
throw new DataAccessResourceFailureException("Unable to obtain a transactional EntityManager");
}
doWrite(entityManager, items);
entityManager.flush();
}
/**
* Do perform the actual write operation. This can be overridden in a
* subclass if necessary.
*
* @param entityManager the EntityManager to use for the operation
* @param items the list of items to use for the write
*/
protected void doWrite(EntityManager entityManager, List<? extends T> items) {
if (logger.isDebugEnabled()) {
logger.debug("Writing to JPA with " + items.size() + " items.");
}
if (!items.isEmpty()) {
long mergeCount = 0;
for (T item : items) {
if (!entityManager.contains(item)) {
entityManager.merge(item);
mergeCount++;
}
}
if (logger.isDebugEnabled()) {
logger.debug(mergeCount + " entities merged.");
logger.debug((items.size() - mergeCount) + " entities found in persistence context.");
}
}
}
}