/*
 * Copyright 2002-2017 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
 *
 *      https://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.orm.jpa.support;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;
import org.springframework.orm.jpa.EntityManagerFactoryAccessor;
import org.springframework.orm.jpa.EntityManagerFactoryInfo;
import org.springframework.orm.jpa.SharedEntityManagerCreator;
import org.springframework.util.Assert;

FactoryBean that exposes a shared JPA EntityManager reference for a given EntityManagerFactory. Typically used for an EntityManagerFactory created by LocalContainerEntityManagerFactoryBean, as direct alternative to a JNDI lookup for a Java EE server's EntityManager reference. 
The shared EntityManager will behave just like an EntityManager fetched from an
application server's JNDI environment, as defined by the JPA specification.
It will delegate all calls to the current transactional EntityManager, if any;
otherwise, it will fall back to a newly created EntityManager per operation.
Can be passed to DAOs that expect a shared EntityManager reference rather than an EntityManagerFactory. Note that Spring's JpaTransactionManager always needs an EntityManagerFactory in order to create new transactional EntityManager instances. 
Author:
Juergen Hoeller
See Also:
setEntityManagerFactory
setEntityManagerInterface
LocalEntityManagerFactoryBean
JpaTransactionManager
Since:
2.0/**
 * {@link FactoryBean} that exposes a shared JPA {@link javax.persistence.EntityManager}
 * reference for a given EntityManagerFactory. Typically used for an EntityManagerFactory
 * created by {@link org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean},
 * as direct alternative to a JNDI lookup for a Java EE server's EntityManager reference.
 *
 * <p>The shared EntityManager will behave just like an EntityManager fetched from an
 * application server's JNDI environment, as defined by the JPA specification.
 * It will delegate all calls to the current transactional EntityManager, if any;
 * otherwise, it will fall back to a newly created EntityManager per operation.
 *
 * <p>Can be passed to DAOs that expect a shared EntityManager reference rather than an
 * EntityManagerFactory. Note that Spring's {@link org.springframework.orm.jpa.JpaTransactionManager}
 * always needs an EntityManagerFactory in order to create new transactional EntityManager instances.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see #setEntityManagerFactory
 * @see #setEntityManagerInterface
 * @see org.springframework.orm.jpa.LocalEntityManagerFactoryBean
 * @see org.springframework.orm.jpa.JpaTransactionManager
 */
public class SharedEntityManagerBean extends EntityManagerFactoryAccessor
		implements FactoryBean<EntityManager>, InitializingBean {

	@Nullable
	private Class<? extends EntityManager> entityManagerInterface;

	private boolean synchronizedWithTransaction = true;

	@Nullable
	private EntityManager shared;


	
Specify the EntityManager interface to expose.
Default is the EntityManager interface as defined by the EntityManagerFactoryInfo, if available. Else, the standard javax.persistence.EntityManager interface will be used. 
See Also:
EntityManagerFactoryInfo.getEntityManagerInterface()
EntityManager/**
	 * Specify the EntityManager interface to expose.
	 * <p>Default is the EntityManager interface as defined by the
	 * EntityManagerFactoryInfo, if available. Else, the standard
	 * {@code javax.persistence.EntityManager} interface will be used.
	 * @see org.springframework.orm.jpa.EntityManagerFactoryInfo#getEntityManagerInterface()
	 * @see javax.persistence.EntityManager
	 */
	public void setEntityManagerInterface(Class<? extends EntityManager> entityManagerInterface) {
		Assert.notNull(entityManagerInterface, "'entityManagerInterface' must not be null");
		this.entityManagerInterface = entityManagerInterface;
	}

	
Set whether to automatically join ongoing transactions (according
to the JPA 2.1 SynchronizationType rules). Default is "true".
/**
	 * Set whether to automatically join ongoing transactions (according
	 * to the JPA 2.1 SynchronizationType rules). Default is "true".
	 */
	public void setSynchronizedWithTransaction(boolean synchronizedWithTransaction) {
		this.synchronizedWithTransaction = synchronizedWithTransaction;
	}


	@Override
	public final void afterPropertiesSet() {
		EntityManagerFactory emf = getEntityManagerFactory();
		if (emf == null) {
			throw new IllegalArgumentException("'entityManagerFactory' or 'persistenceUnitName' is required");
		}
		if (emf instanceof EntityManagerFactoryInfo) {
			EntityManagerFactoryInfo emfInfo = (EntityManagerFactoryInfo) emf;
			if (this.entityManagerInterface == null) {
				this.entityManagerInterface = emfInfo.getEntityManagerInterface();
				if (this.entityManagerInterface == null) {
					this.entityManagerInterface = EntityManager.class;
				}
			}
		}
		else {
			if (this.entityManagerInterface == null) {
				this.entityManagerInterface = EntityManager.class;
			}
		}
		this.shared = SharedEntityManagerCreator.createSharedEntityManager(
				emf, getJpaPropertyMap(), this.synchronizedWithTransaction, this.entityManagerInterface);
	}


	@Override
	@Nullable
	public EntityManager getObject() {
		return this.shared;
	}

	@Override
	public Class<? extends EntityManager> getObjectType() {
		return (this.entityManagerInterface != null ? this.entityManagerInterface : EntityManager.class);
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

}