/*
 * Copyright 2002-2013 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.orm.hibernate3;

import java.sql.Connection;
import javax.sql.DataSource;

import org.hibernate.ConnectionReleaseMode;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.Interceptor;
import org.hibernate.JDBCException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.exception.GenericJDBCException;
import org.hibernate.impl.SessionImpl;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.jdbc.datasource.ConnectionHolder;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.jdbc.datasource.JdbcTransactionObjectSupport;
import org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy;
import org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator;
import org.springframework.jdbc.support.SQLExceptionTranslator;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.IllegalTransactionStateException;
import org.springframework.transaction.InvalidIsolationLevelException;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.support.AbstractPlatformTransactionManager;
import org.springframework.transaction.support.DefaultTransactionStatus;
import org.springframework.transaction.support.ResourceTransactionManager;
import org.springframework.transaction.support.TransactionSynchronizationManager;

/**
 * {@link org.springframework.transaction.PlatformTransactionManager}
 * implementation for a single Hibernate {@link org.hibernate.SessionFactory}.
 * Binds a Hibernate Session from the specified factory to the thread, potentially
 * allowing for one thread-bound Session per factory. {@link SessionFactoryUtils}
 * and {@link HibernateTemplate} are aware of thread-bound Sessions and participate
 * in such transactions automatically. Using either of those or going through
 * {@code SessionFactory.getCurrentSession()} is required for Hibernate
 * access code that needs to support this transaction handling mechanism.
 *
 * <p>Supports custom isolation levels, and timeouts that get applied as
 * Hibernate transaction timeouts.
 *
 * <p>This transaction manager is appropriate for applications that use a single
 * Hibernate SessionFactory for transactional data access, but it also supports
 * direct DataSource access within a transaction (i.e. plain JDBC code working
 * with the same DataSource). This allows for mixing services which access Hibernate
 * and services which use plain JDBC (without being aware of Hibernate)!
 * Application code needs to stick to the same simple Connection lookup pattern as
 * with {@link org.springframework.jdbc.datasource.DataSourceTransactionManager}
 * (i.e. {@link org.springframework.jdbc.datasource.DataSourceUtils#getConnection}
 * or going through a
 * {@link org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy}).
 *
 * <p>Note: To be able to register a DataSource's Connection for plain JDBC code,
 * this instance needs to be aware of the DataSource ({@link #setDataSource}).
 * The given DataSource should obviously match the one used by the given
 * SessionFactory. To achieve this, configure both to the same JNDI DataSource,
 * or preferably create the SessionFactory with {@link LocalSessionFactoryBean} and
 * a local DataSource (which will be autodetected by this transaction manager).
 *
 * <p>JTA (usually through {@link org.springframework.transaction.jta.JtaTransactionManager})
 * is necessary for accessing multiple transactional resources within the same
 * transaction. The DataSource that Hibernate uses needs to be JTA-enabled in
 * such a scenario (see container setup). Normally, JTA setup for Hibernate is
 * somewhat container-specific due to the JTA TransactionManager lookup, required
 * for proper transactional handling of the SessionFactory-level read-write cache.
 *
 * <p>Fortunately, there is an easier way with Spring: {@link SessionFactoryUtils}
 * (and thus {@link HibernateTemplate}) registers synchronizations with Spring's
 * {@link org.springframework.transaction.support.TransactionSynchronizationManager}
 * (as used by {@link org.springframework.transaction.jta.JtaTransactionManager}),
 * for proper after-completion callbacks. Therefore, as long as Spring's
 * JtaTransactionManager drives the JTA transactions, Hibernate does not require
 * any special configuration for proper JTA participation. Note that there are
 * special restrictions with EJB CMT and restrictive JTA subsystems: See
 * {@link org.springframework.transaction.jta.JtaTransactionManager}'s javadoc for details.
 *
 * <p>On JDBC 3.0, this transaction manager supports nested transactions via JDBC 3.0
 * Savepoints. The {@link #setNestedTransactionAllowed} "nestedTransactionAllowed"}
 * flag defaults to "false", though, as nested transactions will just apply to the
 * JDBC Connection, not to the Hibernate Session and its cached objects. You can
 * manually set the flag to "true" if you want to use nested transactions for
 * JDBC access code which participates in Hibernate transactions (provided that
 * your JDBC driver supports Savepoints). <i>Note that Hibernate itself does not
 * support nested transactions! Hence, do not expect Hibernate access code to
 * semantically participate in a nested transaction.</i>
 *
 * <p>Requires Hibernate 3.2 or later, as of Spring 3.0.
 *
 * @author Juergen Hoeller
 * @since 1.2
 * @see #setSessionFactory
 * @see #setDataSource
 * @see LocalSessionFactoryBean
 * @see SessionFactoryUtils#getSession
 * @see SessionFactoryUtils#applyTransactionTimeout
 * @see SessionFactoryUtils#releaseSession
 * @see HibernateTemplate
 * @see org.hibernate.SessionFactory#getCurrentSession()
 * @see org.springframework.jdbc.datasource.DataSourceUtils#getConnection
 * @see org.springframework.jdbc.datasource.DataSourceUtils#applyTransactionTimeout
 * @see org.springframework.jdbc.datasource.DataSourceUtils#releaseConnection
 * @see org.springframework.jdbc.core.JdbcTemplate
 * @see org.springframework.jdbc.datasource.DataSourceTransactionManager
 * @see org.springframework.transaction.jta.JtaTransactionManager
 */
@SuppressWarnings("serial")
public class HibernateTransactionManager extends AbstractPlatformTransactionManager
		implements ResourceTransactionManager, BeanFactoryAware, InitializingBean {

	private SessionFactory sessionFactory;

	private DataSource dataSource;

	private boolean autodetectDataSource = true;

	private boolean prepareConnection = true;

	private boolean hibernateManagedSession = false;

	private boolean earlyFlushBeforeCommit = false;

	private Object entityInterceptor;

	private SQLExceptionTranslator jdbcExceptionTranslator;

	private SQLExceptionTranslator defaultJdbcExceptionTranslator;

	/**
	 * Just needed for entityInterceptorBeanName.
	 * @see #setEntityInterceptorBeanName
	 */
	private BeanFactory beanFactory;


	/**
	 * Create a new HibernateTransactionManager instance.
	 * A SessionFactory has to be set to be able to use it.
	 * @see #setSessionFactory
	 */
	public HibernateTransactionManager() {
	}

	/**
	 * Create a new HibernateTransactionManager instance.
	 * @param sessionFactory SessionFactory to manage transactions for
	 */
	public HibernateTransactionManager(SessionFactory sessionFactory) {
		this.sessionFactory = sessionFactory;
		afterPropertiesSet();
	}


	/**
	 * Set the SessionFactory that this instance should manage transactions for.
	 */
	public void setSessionFactory(SessionFactory sessionFactory) {
		this.sessionFactory = sessionFactory;
	}

	/**
	 * Return the SessionFactory that this instance should manage transactions for.
	 */
	public SessionFactory getSessionFactory() {
		return this.sessionFactory;
	}

	/**
	 * Set the JDBC DataSource that this instance should manage transactions for.
	 * The DataSource should match the one used by the Hibernate SessionFactory:
	 * for example, you could specify the same JNDI DataSource for both.
	 * <p>If the SessionFactory was configured with LocalDataSourceConnectionProvider,
	 * i.e. by Spring's LocalSessionFactoryBean with a specified "dataSource",
	 * the DataSource will be auto-detected: You can still explicitly specify the
	 * DataSource, but you don't need to in this case.
	 * <p>A transactional JDBC Connection for this DataSource will be provided to
	 * application code accessing this DataSource directly via DataSourceUtils
	 * or JdbcTemplate. The Connection will be taken from the Hibernate Session.
	 * <p>The DataSource specified here should be the target DataSource to manage
	 * transactions for, not a TransactionAwareDataSourceProxy. Only data access
	 * code may work with TransactionAwareDataSourceProxy, while the transaction
	 * manager needs to work on the underlying target DataSource. If there's
	 * nevertheless a TransactionAwareDataSourceProxy passed in, it will be
	 * unwrapped to extract its target DataSource.
	 * @see #setAutodetectDataSource
	 * @see LocalDataSourceConnectionProvider
	 * @see LocalSessionFactoryBean#setDataSource
	 * @see org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy
	 * @see org.springframework.jdbc.datasource.DataSourceUtils
	 * @see org.springframework.jdbc.core.JdbcTemplate
	 */
	public void setDataSource(DataSource dataSource) {
		if (dataSource instanceof TransactionAwareDataSourceProxy) {
			// If we got a TransactionAwareDataSourceProxy, we need to perform transactions
			// for its underlying target DataSource, else data access code won't see
			// properly exposed transactions (i.e. transactions for the target DataSource).
			this.dataSource = ((TransactionAwareDataSourceProxy) dataSource).getTargetDataSource();
		}
		else {
			this.dataSource = dataSource;
		}
	}

	/**
	 * Return the JDBC DataSource that this instance manages transactions for.
	 */
	public DataSource getDataSource() {
		return this.dataSource;
	}

	/**
	 * Set whether to autodetect a JDBC DataSource used by the Hibernate SessionFactory,
	 * if set via LocalSessionFactoryBean's {@code setDataSource}. Default is "true".
	 * <p>Can be turned off to deliberately ignore an available DataSource, in order
	 * to not expose Hibernate transactions as JDBC transactions for that DataSource.
	 * @see #setDataSource
	 * @see LocalSessionFactoryBean#setDataSource
	 */
	public void setAutodetectDataSource(boolean autodetectDataSource) {
		this.autodetectDataSource = autodetectDataSource;
	}

	/**
	 * Set whether to prepare the underlying JDBC Connection of a transactional
	 * Hibernate Session, that is, whether to apply a transaction-specific
	 * isolation level and/or the transaction's read-only flag to the underlying
	 * JDBC Connection.
	 * <p>Default is "true". If you turn this flag off, the transaction manager
	 * will not support per-transaction isolation levels anymore. It will not
	 * call {@code Connection.setReadOnly(true)} for read-only transactions
	 * anymore either. If this flag is turned off, no cleanup of a JDBC Connection
	 * is required after a transaction, since no Connection settings will get modified.
	 * @see java.sql.Connection#setTransactionIsolation
	 * @see java.sql.Connection#setReadOnly
	 */
	public void setPrepareConnection(boolean prepareConnection) {
		this.prepareConnection = prepareConnection;
	}

	/**
	 * Set whether to operate on a Hibernate-managed Session instead of a
	 * Spring-managed Session, that is, whether to obtain the Session through
	 * Hibernate's {@link org.hibernate.SessionFactory#getCurrentSession()}
	 * instead of {@link org.hibernate.SessionFactory#openSession()} (with a Spring
	 * {@link org.springframework.transaction.support.TransactionSynchronizationManager}
	 * check preceding it).
	 * <p>Default is "false", i.e. using a Spring-managed Session: taking the current
	 * thread-bound Session if available (e.g. in an Open-Session-in-View scenario),
	 * creating a new Session for the current transaction otherwise.
	 * <p>Switch this flag to "true" in order to enforce use of a Hibernate-managed Session.
	 * Note that this requires {@link org.hibernate.SessionFactory#getCurrentSession()}
	 * to always return a proper Session when called for a Spring-managed transaction;
	 * transaction begin will fail if the {@code getCurrentSession()} call fails.
	 * <p>This mode will typically be used in combination with a custom Hibernate
	 * {@link org.hibernate.context.CurrentSessionContext} implementation that stores
	 * Sessions in a place other than Spring's TransactionSynchronizationManager.
	 * It may also be used in combination with Spring's Open-Session-in-View support
	 * (using Spring's default {@link SpringSessionContext}), in which case it subtly
	 * differs from the Spring-managed Session mode: The pre-bound Session will <i>not</i>
	 * receive a {@code clear()} call (on rollback) or a {@code disconnect()}
	 * call (on transaction completion) in such a scenario; this is rather left up
	 * to a custom CurrentSessionContext implementation (if desired).
	 */
	public void setHibernateManagedSession(boolean hibernateManagedSession) {
		this.hibernateManagedSession = hibernateManagedSession;
	}

	/**
	 * Set whether to perform an early flush before proceeding with a commit.
	 * <p>Default is "false", performing an implicit flush as part of the actual
	 * commit step. Switch this to "true" in order to enforce an explicit early
	 * flush right <i>before</i> the actual commit step.
	 * <p>An early flush happens before the before-commit synchronization phase,
	 * making flushed state visible to {@code beforeCommit} callbacks of registered
	 * {@link org.springframework.transaction.support.TransactionSynchronization}
	 * objects. Such explicit flush behavior is consistent with Spring-driven
	 * flushing in a JTA transaction environment, so may also get enforced for
	 * consistency with JTA transaction behavior.
	 * @see #prepareForCommit
	 */
	public void setEarlyFlushBeforeCommit(boolean earlyFlushBeforeCommit) {
		this.earlyFlushBeforeCommit = earlyFlushBeforeCommit;
	}

	/**
	 * Set the bean name of a Hibernate entity interceptor that allows to inspect
	 * and change property values before writing to and reading from the database.
	 * Will get applied to any new Session created by this transaction manager.
	 * <p>Requires the bean factory to be known, to be able to resolve the bean
	 * name to an interceptor instance on session creation. Typically used for
	 * prototype interceptors, i.e. a new interceptor instance per session.
	 * <p>Can also be used for shared interceptor instances, but it is recommended
	 * to set the interceptor reference directly in such a scenario.
	 * @param entityInterceptorBeanName the name of the entity interceptor in
	 * the bean factory
	 * @see #setBeanFactory
	 * @see #setEntityInterceptor
	 */
	public void setEntityInterceptorBeanName(String entityInterceptorBeanName) {
		this.entityInterceptor = entityInterceptorBeanName;
	}

	/**
	 * Set a Hibernate entity interceptor that allows to inspect and change
	 * property values before writing to and reading from the database.
	 * Will get applied to any new Session created by this transaction manager.
	 * <p>Such an interceptor can either be set at the SessionFactory level,
	 * i.e. on LocalSessionFactoryBean, or at the Session level, i.e. on
	 * HibernateTemplate, HibernateInterceptor, and HibernateTransactionManager.
	 * It's preferable to set it on LocalSessionFactoryBean or HibernateTransactionManager
	 * to avoid repeated configuration and guarantee consistent behavior in transactions.
	 * @see LocalSessionFactoryBean#setEntityInterceptor
	 * @see HibernateTemplate#setEntityInterceptor
	 * @see HibernateInterceptor#setEntityInterceptor
	 */
	public void setEntityInterceptor(Interceptor entityInterceptor) {
		this.entityInterceptor = entityInterceptor;
	}

	/**
	 * Return the current Hibernate entity interceptor, or {@code null} if none.
	 * Resolves an entity interceptor bean name via the bean factory,
	 * if necessary.
	 * @throws IllegalStateException if bean name specified but no bean factory set
	 * @throws BeansException if bean name resolution via the bean factory failed
	 * @see #setEntityInterceptor
	 * @see #setEntityInterceptorBeanName
	 * @see #setBeanFactory
	 */
	public Interceptor getEntityInterceptor() throws IllegalStateException, BeansException {
		if (this.entityInterceptor instanceof Interceptor) {
			return (Interceptor) entityInterceptor;
		}
		else if (this.entityInterceptor instanceof String) {
			if (this.beanFactory == null) {
				throw new IllegalStateException("Cannot get entity interceptor via bean name if no bean factory set");
			}
			String beanName = (String) this.entityInterceptor;
			return this.beanFactory.getBean(beanName, Interceptor.class);
		}
		else {
			return null;
		}
	}

	/**
	 * Set the JDBC exception translator for this transaction manager.
	 * <p>Applied to any SQLException root cause of a Hibernate JDBCException that
	 * is thrown on flush, overriding Hibernate's default SQLException translation
	 * (which is based on Hibernate's Dialect for a specific target database).
	 * @param jdbcExceptionTranslator the exception translator
	 * @see java.sql.SQLException
	 * @see org.hibernate.JDBCException
	 * @see org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator
	 * @see org.springframework.jdbc.support.SQLStateSQLExceptionTranslator
	 */
	public void setJdbcExceptionTranslator(SQLExceptionTranslator jdbcExceptionTranslator) {
		this.jdbcExceptionTranslator = jdbcExceptionTranslator;
	}

	/**
	 * Return the JDBC exception translator for this transaction manager, if any.
	 */
	public SQLExceptionTranslator getJdbcExceptionTranslator() {
		return this.jdbcExceptionTranslator;
	}

	/**
	 * The bean factory just needs to be known for resolving entity interceptor
	 * bean names. It does not need to be set for any other mode of operation.
	 * @see #setEntityInterceptorBeanName
	 */
	public void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
	}

	public void afterPropertiesSet() {
		if (getSessionFactory() == null) {
			throw new IllegalArgumentException("Property 'sessionFactory' is required");
		}
		if (this.entityInterceptor instanceof String && this.beanFactory == null) {
			throw new IllegalArgumentException("Property 'beanFactory' is required for 'entityInterceptorBeanName'");
		}

		// Check for SessionFactory's DataSource.
		if (this.autodetectDataSource && getDataSource() == null) {
			DataSource sfds = SessionFactoryUtils.getDataSource(getSessionFactory());
			if (sfds != null) {
				// Use the SessionFactory's DataSource for exposing transactions to JDBC code.
				if (logger.isInfoEnabled()) {
					logger.info("Using DataSource [" + sfds +
							"] of Hibernate SessionFactory for HibernateTransactionManager");
				}
				setDataSource(sfds);
			}
		}
	}


	public Object getResourceFactory() {
		return getSessionFactory();
	}

	@Override
	protected Object doGetTransaction() {
		HibernateTransactionObject txObject = new HibernateTransactionObject();
		txObject.setSavepointAllowed(isNestedTransactionAllowed());

		SessionHolder sessionHolder =
				(SessionHolder) TransactionSynchronizationManager.getResource(getSessionFactory());
		if (sessionHolder != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Found thread-bound Session [" +
						SessionFactoryUtils.toString(sessionHolder.getSession()) + "] for Hibernate transaction");
			}
			txObject.setSessionHolder(sessionHolder);
		}
		else if (this.hibernateManagedSession) {
			try {
				Session session = getSessionFactory().getCurrentSession();
				if (logger.isDebugEnabled()) {
					logger.debug("Found Hibernate-managed Session [" +
							SessionFactoryUtils.toString(session) + "] for Spring-managed transaction");
				}
				txObject.setExistingSession(session);
			}
			catch (HibernateException ex) {
				throw new DataAccessResourceFailureException(
						"Could not obtain Hibernate-managed Session for Spring-managed transaction", ex);
			}
		}

		if (getDataSource() != null) {
			ConnectionHolder conHolder = (ConnectionHolder)
					TransactionSynchronizationManager.getResource(getDataSource());
			txObject.setConnectionHolder(conHolder);
		}

		return txObject;
	}

	@Override
	protected boolean isExistingTransaction(Object transaction) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;
		return (txObject.hasSpringManagedTransaction() ||
				(this.hibernateManagedSession && txObject.hasHibernateManagedTransaction()));
	}

	@Override
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;

		if (txObject.hasConnectionHolder() && !txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
			throw new IllegalTransactionStateException(
					"Pre-bound JDBC Connection found! HibernateTransactionManager does not support " +
					"running within DataSourceTransactionManager if told to manage the DataSource itself. " +
					"It is recommended to use a single HibernateTransactionManager for all transactions " +
					"on a single DataSource, no matter whether Hibernate or JDBC access.");
		}

		Session session = null;

		try {
			if (txObject.getSessionHolder() == null || txObject.getSessionHolder().isSynchronizedWithTransaction()) {
				Interceptor entityInterceptor = getEntityInterceptor();
				Session newSession = (entityInterceptor != null ?
						getSessionFactory().openSession(entityInterceptor) : getSessionFactory().openSession());
				if (logger.isDebugEnabled()) {
					logger.debug("Opened new Session [" + SessionFactoryUtils.toString(newSession) +
							"] for Hibernate transaction");
				}
				txObject.setSession(newSession);
			}

			session = txObject.getSessionHolder().getSession();

			if (this.prepareConnection && isSameConnectionForEntireSession(session)) {
				// We're allowed to change the transaction settings of the JDBC Connection.
				if (logger.isDebugEnabled()) {
					logger.debug(
							"Preparing JDBC Connection of Hibernate Session [" + SessionFactoryUtils.toString(session) + "]");
				}
				Connection con = session.connection();
				Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
				txObject.setPreviousIsolationLevel(previousIsolationLevel);
			}
			else {
				// Not allowed to change the transaction settings of the JDBC Connection.
				if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) {
					// We should set a specific isolation level but are not allowed to...
					throw new InvalidIsolationLevelException(
							"HibernateTransactionManager is not allowed to support custom isolation levels: " +
							"make sure that its 'prepareConnection' flag is on (the default) and that the " +
							"Hibernate connection release mode is set to 'on_close' (SpringTransactionFactory's default). " +
							"Make sure that your LocalSessionFactoryBean actually uses SpringTransactionFactory: Your " +
							"Hibernate properties should *not* include a 'hibernate.transaction.factory_class' property!");
				}
				if (logger.isDebugEnabled()) {
					logger.debug(
							"Not preparing JDBC Connection of Hibernate Session [" + SessionFactoryUtils.toString(session) + "]");
				}
			}

			if (definition.isReadOnly() && txObject.isNewSession()) {
				// Just set to MANUAL in case of a new Session for this transaction.
				session.setFlushMode(FlushMode.MANUAL);
			}

			if (!definition.isReadOnly() && !txObject.isNewSession()) {
				// We need AUTO or COMMIT for a non-read-only transaction.
				FlushMode flushMode = session.getFlushMode();
				if (flushMode.lessThan(FlushMode.COMMIT)) {
					session.setFlushMode(FlushMode.AUTO);
					txObject.getSessionHolder().setPreviousFlushMode(flushMode);
				}
			}

			Transaction hibTx;

			// Register transaction timeout.
			int timeout = determineTimeout(definition);
			if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
				// Use Hibernate's own transaction timeout mechanism on Hibernate 3.1+
				// Applies to all statements, also to inserts, updates and deletes!
				hibTx = session.getTransaction();
				hibTx.setTimeout(timeout);
				hibTx.begin();
			}
			else {
				// Open a plain Hibernate transaction without specified timeout.
				hibTx = session.beginTransaction();
			}

			// Add the Hibernate transaction to the session holder.
			txObject.getSessionHolder().setTransaction(hibTx);

			// Register the Hibernate Session's JDBC Connection for the DataSource, if set.
			if (getDataSource() != null) {
				Connection con = session.connection();
				ConnectionHolder conHolder = new ConnectionHolder(con);
				if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
					conHolder.setTimeoutInSeconds(timeout);
				}
				if (logger.isDebugEnabled()) {
					logger.debug("Exposing Hibernate transaction as JDBC transaction [" + con + "]");
				}
				TransactionSynchronizationManager.bindResource(getDataSource(), conHolder);
				txObject.setConnectionHolder(conHolder);
			}

			// Bind the session holder to the thread.
			if (txObject.isNewSessionHolder()) {
				TransactionSynchronizationManager.bindResource(getSessionFactory(), txObject.getSessionHolder());
			}
			txObject.getSessionHolder().setSynchronizedWithTransaction(true);
		}

		catch (Throwable ex) {
			if (txObject.isNewSession()) {
				try {
					if (session.getTransaction().isActive()) {
						session.getTransaction().rollback();
					}
				}
				catch (Throwable ex2) {
					logger.debug("Could not rollback Session after failed transaction begin", ex);
				}
				finally {
					SessionFactoryUtils.closeSession(session);
				}
			}
			throw new CannotCreateTransactionException("Could not open Hibernate Session for transaction", ex);
		}
	}

	@Override
	protected Object doSuspend(Object transaction) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;
		txObject.setSessionHolder(null);
		SessionHolder sessionHolder =
				(SessionHolder) TransactionSynchronizationManager.unbindResource(getSessionFactory());
		txObject.setConnectionHolder(null);
		ConnectionHolder connectionHolder = null;
		if (getDataSource() != null) {
			connectionHolder = (ConnectionHolder) TransactionSynchronizationManager.unbindResource(getDataSource());
		}
		return new SuspendedResourcesHolder(sessionHolder, connectionHolder);
	}

	@Override
	protected void doResume(Object transaction, Object suspendedResources) {
		SuspendedResourcesHolder resourcesHolder = (SuspendedResourcesHolder) suspendedResources;
		if (TransactionSynchronizationManager.hasResource(getSessionFactory())) {
			// From non-transactional code running in active transaction synchronization
			// -> can be safely removed, will be closed on transaction completion.
			TransactionSynchronizationManager.unbindResource(getSessionFactory());
		}
		TransactionSynchronizationManager.bindResource(getSessionFactory(), resourcesHolder.getSessionHolder());
		if (getDataSource() != null) {
			TransactionSynchronizationManager.bindResource(getDataSource(), resourcesHolder.getConnectionHolder());
		}
	}

	@Override
	protected void prepareForCommit(DefaultTransactionStatus status) {
		if (this.earlyFlushBeforeCommit && status.isNewTransaction()) {
			HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
			Session session = txObject.getSessionHolder().getSession();
			if (!session.getFlushMode().lessThan(FlushMode.COMMIT)) {
				logger.debug("Performing an early flush for Hibernate transaction");
				try {
					session.flush();
				}
				catch (HibernateException ex) {
					throw convertHibernateAccessException(ex);
				}
				finally {
					session.setFlushMode(FlushMode.MANUAL);
				}
			}
		}
	}

	@Override
	protected void doCommit(DefaultTransactionStatus status) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Committing Hibernate transaction on Session [" +
					SessionFactoryUtils.toString(txObject.getSessionHolder().getSession()) + "]");
		}
		try {
			txObject.getSessionHolder().getTransaction().commit();
		}
		catch (org.hibernate.TransactionException ex) {
			// assumably from commit call to the underlying JDBC connection
			throw new TransactionSystemException("Could not commit Hibernate transaction", ex);
		}
		catch (HibernateException ex) {
			// assumably failed to flush changes to database
			throw convertHibernateAccessException(ex);
		}
	}

	@Override
	protected void doRollback(DefaultTransactionStatus status) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Rolling back Hibernate transaction on Session [" +
					SessionFactoryUtils.toString(txObject.getSessionHolder().getSession()) + "]");
		}
		try {
			txObject.getSessionHolder().getTransaction().rollback();
		}
		catch (org.hibernate.TransactionException ex) {
			throw new TransactionSystemException("Could not roll back Hibernate transaction", ex);
		}
		catch (HibernateException ex) {
			// Shouldn't really happen, as a rollback doesn't cause a flush.
			throw convertHibernateAccessException(ex);
		}
		finally {
			if (!txObject.isNewSession() && !this.hibernateManagedSession) {
				// Clear all pending inserts/updates/deletes in the Session.
				// Necessary for pre-bound Sessions, to avoid inconsistent state.
				txObject.getSessionHolder().getSession().clear();
			}
		}
	}

	@Override
	protected void doSetRollbackOnly(DefaultTransactionStatus status) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Setting Hibernate transaction on Session [" +
					SessionFactoryUtils.toString(txObject.getSessionHolder().getSession()) + "] rollback-only");
		}
		txObject.setRollbackOnly();
	}

	@Override
	protected void doCleanupAfterCompletion(Object transaction) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;

		// Remove the session holder from the thread.
		if (txObject.isNewSessionHolder()) {
			TransactionSynchronizationManager.unbindResource(getSessionFactory());
		}

		// Remove the JDBC connection holder from the thread, if exposed.
		if (getDataSource() != null) {
			TransactionSynchronizationManager.unbindResource(getDataSource());
		}

		Session session = txObject.getSessionHolder().getSession();
		if (this.prepareConnection && session.isConnected() && isSameConnectionForEntireSession(session)) {
			// We're running with connection release mode "on_close": We're able to reset
			// the isolation level and/or read-only flag of the JDBC Connection here.
			// Else, we need to rely on the connection pool to perform proper cleanup.
			try {
				Connection con = session.connection();
				DataSourceUtils.resetConnectionAfterTransaction(con, txObject.getPreviousIsolationLevel());
			}
			catch (HibernateException ex) {
				logger.debug("Could not access JDBC Connection of Hibernate Session", ex);
			}
		}

		if (txObject.isNewSession()) {
			if (logger.isDebugEnabled()) {
				logger.debug("Closing Hibernate Session [" + SessionFactoryUtils.toString(session) +
						"] after transaction");
			}
			SessionFactoryUtils.closeSessionOrRegisterDeferredClose(session, getSessionFactory());
		}
		else {
			if (logger.isDebugEnabled()) {
				logger.debug("Not closing pre-bound Hibernate Session [" +
						SessionFactoryUtils.toString(session) + "] after transaction");
			}
			if (txObject.getSessionHolder().getPreviousFlushMode() != null) {
				session.setFlushMode(txObject.getSessionHolder().getPreviousFlushMode());
			}
			if (!this.hibernateManagedSession) {
				session.disconnect();
			}
		}
		txObject.getSessionHolder().clear();
	}

	/**
	 * Return whether the given Hibernate Session will always hold the same
	 * JDBC Connection. This is used to check whether the transaction manager
	 * can safely prepare and clean up the JDBC Connection used for a transaction.
	 * <p>Default implementation checks the Session's connection release mode
	 * to be "on_close". Unfortunately, this requires casting to SessionImpl,
	 * as of Hibernate 3.1. If that cast doesn't work, we'll simply assume
	 * we're safe and return {@code true}.
	 * @param session the Hibernate Session to check
	 * @see org.hibernate.impl.SessionImpl#getConnectionReleaseMode()
	 * @see org.hibernate.ConnectionReleaseMode#ON_CLOSE
	 */
	protected boolean isSameConnectionForEntireSession(Session session) {
		if (!(session instanceof SessionImpl)) {
			// The best we can do is to assume we're safe.
			return true;
		}
		ConnectionReleaseMode releaseMode = ((SessionImpl) session).getConnectionReleaseMode();
		return ConnectionReleaseMode.ON_CLOSE.equals(releaseMode);
	}


	/**
	 * Convert the given HibernateException to an appropriate exception
	 * from the {@code org.springframework.dao} hierarchy.
	 * <p>Will automatically apply a specified SQLExceptionTranslator to a
	 * Hibernate JDBCException, else rely on Hibernate's default translation.
	 * @param ex HibernateException that occurred
	 * @return a corresponding DataAccessException
	 * @see SessionFactoryUtils#convertHibernateAccessException
	 * @see #setJdbcExceptionTranslator
	 */
	protected DataAccessException convertHibernateAccessException(HibernateException ex) {
		if (getJdbcExceptionTranslator() != null && ex instanceof JDBCException) {
			return convertJdbcAccessException((JDBCException) ex, getJdbcExceptionTranslator());
		}
		else if (GenericJDBCException.class.equals(ex.getClass())) {
			return convertJdbcAccessException((GenericJDBCException) ex, getDefaultJdbcExceptionTranslator());
		}
		return SessionFactoryUtils.convertHibernateAccessException(ex);
	}

	/**
	 * Convert the given Hibernate JDBCException to an appropriate exception
	 * from the {@code org.springframework.dao} hierarchy, using the
	 * given SQLExceptionTranslator.
	 * @param ex Hibernate JDBCException that occurred
	 * @param translator the SQLExceptionTranslator to use
	 * @return a corresponding DataAccessException
	 */
	protected DataAccessException convertJdbcAccessException(JDBCException ex, SQLExceptionTranslator translator) {
		return translator.translate("Hibernate flushing: " + ex.getMessage(), ex.getSQL(), ex.getSQLException());
	}

	/**
	 * Obtain a default SQLExceptionTranslator, lazily creating it if necessary.
	 * <p>Creates a default
	 * {@link org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator}
	 * for the SessionFactory's underlying DataSource.
	 */
	protected synchronized SQLExceptionTranslator getDefaultJdbcExceptionTranslator() {
		if (this.defaultJdbcExceptionTranslator == null) {
			if (getDataSource() != null) {
				this.defaultJdbcExceptionTranslator = new SQLErrorCodeSQLExceptionTranslator(getDataSource());
			}
			else {
				this.defaultJdbcExceptionTranslator = SessionFactoryUtils.newJdbcExceptionTranslator(getSessionFactory());
			}
		}
		return this.defaultJdbcExceptionTranslator;
	}


	/**
	 * Hibernate transaction object, representing a SessionHolder.
	 * Used as transaction object by HibernateTransactionManager.
	 */
	private class HibernateTransactionObject extends JdbcTransactionObjectSupport {

		private SessionHolder sessionHolder;

		private boolean newSessionHolder;

		private boolean newSession;

		public void setSession(Session session) {
			this.sessionHolder = new SessionHolder(session);
			this.newSessionHolder = true;
			this.newSession = true;
		}

		public void setExistingSession(Session session) {
			this.sessionHolder = new SessionHolder(session);
			this.newSessionHolder = true;
			this.newSession = false;
		}

		public void setSessionHolder(SessionHolder sessionHolder) {
			this.sessionHolder = sessionHolder;
			this.newSessionHolder = false;
			this.newSession = false;
		}

		public SessionHolder getSessionHolder() {
			return this.sessionHolder;
		}

		public boolean isNewSessionHolder() {
			return this.newSessionHolder;
		}

		public boolean isNewSession() {
			return this.newSession;
		}

		public boolean hasSpringManagedTransaction() {
			return (this.sessionHolder != null && this.sessionHolder.getTransaction() != null);
		}

		public boolean hasHibernateManagedTransaction() {
			return (this.sessionHolder != null && this.sessionHolder.getSession().getTransaction().isActive());
		}

		public void setRollbackOnly() {
			this.sessionHolder.setRollbackOnly();
			if (hasConnectionHolder()) {
				getConnectionHolder().setRollbackOnly();
			}
		}

		public boolean isRollbackOnly() {
			return this.sessionHolder.isRollbackOnly() ||
					(hasConnectionHolder() && getConnectionHolder().isRollbackOnly());
		}

		@Override
		public void flush() {
			try {
				this.sessionHolder.getSession().flush();
			}
			catch (HibernateException ex) {
				throw convertHibernateAccessException(ex);
			}
		}
	}


	/**
	 * Holder for suspended resources.
	 * Used internally by {@code doSuspend} and {@code doResume}.
	 */
	private static class SuspendedResourcesHolder {

		private final SessionHolder sessionHolder;

		private final ConnectionHolder connectionHolder;

		private SuspendedResourcesHolder(SessionHolder sessionHolder, ConnectionHolder conHolder) {
			this.sessionHolder = sessionHolder;
			this.connectionHolder = conHolder;
		}

		private SessionHolder getSessionHolder() {
			return this.sessionHolder;
		}

		private ConnectionHolder getConnectionHolder() {
			return this.connectionHolder;
		}
	}

}
