org.springframework.batch.item.database.JpaItemWriter.java Source code

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Here is the source code for org.springframework.batch.item.database.JpaItemWriter.java

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/*
 * 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.");
            }
        }

    }

}