/*
 * Copyright 2002-2014 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.transaction.jta;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.List;
import java.util.Properties;
import javax.naming.NamingException;
import javax.transaction.HeuristicMixedException;
import javax.transaction.HeuristicRollbackException;
import javax.transaction.InvalidTransactionException;
import javax.transaction.NotSupportedException;
import javax.transaction.RollbackException;
import javax.transaction.Status;
import javax.transaction.Synchronization;
import javax.transaction.SystemException;
import javax.transaction.Transaction;
import javax.transaction.TransactionManager;
import javax.transaction.TransactionSynchronizationRegistry;
import javax.transaction.UserTransaction;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.jndi.JndiTemplate;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.HeuristicCompletionException;
import org.springframework.transaction.IllegalTransactionStateException;
import org.springframework.transaction.InvalidIsolationLevelException;
import org.springframework.transaction.NestedTransactionNotSupportedException;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionSuspensionNotSupportedException;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.UnexpectedRollbackException;
import org.springframework.transaction.support.AbstractPlatformTransactionManager;
import org.springframework.transaction.support.DefaultTransactionStatus;
import org.springframework.transaction.support.TransactionSynchronization;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.springframework.transaction.PlatformTransactionManager} implementation
 * for JTA, delegating to a backend JTA provider. This is typically used to delegate
 * to a Java EE server's transaction coordinator, but may also be configured with a
 * local JTA provider which is embedded within the application.
 *
 * <p>This transaction manager is appropriate for handling distributed transactions,
 * i.e. transactions that span multiple resources, and for controlling transactions on
 * application server resources (e.g. JDBC DataSources available in JNDI) in general.
 * For a single JDBC DataSource, DataSourceTransactionManager is perfectly sufficient,
 * and for accessing a single resource with Hibernate (including transactional cache),
 * HibernateTransactionManager is appropriate, for example.
 *
 * <p><b>For typical JTA transactions (REQUIRED, SUPPORTS, MANDATORY, NEVER), a plain
 * JtaTransactionManager definition is all you need, portable across all Java EE servers.</b>
 * This corresponds to the functionality of the JTA UserTransaction, for which Java EE
 * specifies a standard JNDI name ("java:comp/UserTransaction"). There is no need to
 * configure a server-specific TransactionManager lookup for this kind of JTA usage.
 *
 * <p><b>Transaction suspension (REQUIRES_NEW, NOT_SUPPORTED) is just available with a
 * JTA TransactionManager being registered.</b> Common TransactionManager locations are
 * autodetected by JtaTransactionManager, provided that the "autodetectTransactionManager"
 * flag is set to "true" (which it is by default).
 *
 * <p>Note: Support for the JTA TransactionManager interface is not required by Java EE.
 * Almost all Java EE servers expose it, but do so as extension to EE. There might be some
 * issues with compatibility, despite the TransactionManager interface being part of JTA.
 * As a consequence, Spring provides various vendor-specific PlatformTransactionManagers,
 * which are recommended to be used if appropriate: {@link WebLogicJtaTransactionManager},
 * {@link WebSphereUowTransactionManager} and {@link OC4JJtaTransactionManager}.
 * For all other Java EE servers, the standard JtaTransactionManager is sufficient.
 *
 * <p>This pure JtaTransactionManager class supports timeouts but not per-transaction
 * isolation levels. Custom subclasses may override the {@link #doJtaBegin} method for
 * specific JTA extensions in order to provide this functionality; Spring includes
 * corresponding {@link WebLogicJtaTransactionManager} and {@link OC4JJtaTransactionManager}
 * classes, for BEA's WebLogic Server and Oracle's OC4J, respectively. Such adapters
 * for specific Java EE transaction coordinators may also expose transaction names for
 * monitoring; with standard JTA, transaction names will simply be ignored.
 *
 * <p><b>Consider using Spring's {@code tx:jta-transaction-manager} configuration
 * element for automatically picking the appropriate JTA platform transaction manager
 * (automatically detecting WebLogic, WebSphere and OC4J).</b>
 *
 * <p>JTA 1.1 adds the TransactionSynchronizationRegistry facility, as public Java EE 5
 * API in addition to the standard JTA UserTransaction handle. As of Spring 2.5, this
 * JtaTransactionManager autodetects the TransactionSynchronizationRegistry and uses
 * it for registering Spring-managed synchronizations when participating in an existing
 * JTA transaction (e.g. controlled by EJB CMT). If no TransactionSynchronizationRegistry
 * is available (or the JTA 1.1 API isn't available), then such synchronizations
 * will be registered via the (non-EE) JTA TransactionManager handle.
 *
 * <p>This class is serializable. However, active synchronizations do not survive serialization.
 *
 * @author Juergen Hoeller
 * @since 24.03.2003
 * @see javax.transaction.UserTransaction
 * @see javax.transaction.TransactionManager
 * @see javax.transaction.TransactionSynchronizationRegistry
 * @see #setUserTransactionName
 * @see #setUserTransaction
 * @see #setTransactionManagerName
 * @see #setTransactionManager
 * @see WebLogicJtaTransactionManager
 */
@SuppressWarnings("serial")
public class JtaTransactionManager extends AbstractPlatformTransactionManager
		implements TransactionFactory, InitializingBean, Serializable {

	/**
	 * Default JNDI location for the JTA UserTransaction. Many Java EE servers
	 * also provide support for the JTA TransactionManager interface there.
	 * @see #setUserTransactionName
	 * @see #setAutodetectTransactionManager
	 */
	public static final String DEFAULT_USER_TRANSACTION_NAME = "java:comp/UserTransaction";

	/**
	 * Fallback JNDI locations for the JTA TransactionManager. Applied if
	 * the JTA UserTransaction does not implement the JTA TransactionManager
	 * interface, provided that the "autodetectTransactionManager" flag is "true".
	 * @see #setTransactionManagerName
	 * @see #setAutodetectTransactionManager
	 */
	public static final String[] FALLBACK_TRANSACTION_MANAGER_NAMES =
			new String[] {"java:comp/TransactionManager", "java:appserver/TransactionManager",
					"java:pm/TransactionManager", "java:/TransactionManager"};

	/**
	 * Standard Java EE 5 JNDI location for the JTA TransactionSynchronizationRegistry.
	 * Autodetected when available.
	 */
	public static final String DEFAULT_TRANSACTION_SYNCHRONIZATION_REGISTRY_NAME =
			"java:comp/TransactionSynchronizationRegistry";


	private static final String TRANSACTION_SYNCHRONIZATION_REGISTRY_CLASS_NAME =
			"javax.transaction.TransactionSynchronizationRegistry";

	private static Class<?> transactionSynchronizationRegistryClass;

	static {
		try {
			transactionSynchronizationRegistryClass = ClassUtils.forName(
					TRANSACTION_SYNCHRONIZATION_REGISTRY_CLASS_NAME, JtaTransactionManager.class.getClassLoader());
		}
		catch (ClassNotFoundException ex) {
			// JTA 1.1 API not available... simply proceed the JTA 1.0 way.
		}
	}


	private transient JndiTemplate jndiTemplate = new JndiTemplate();

	private transient UserTransaction userTransaction;

	private String userTransactionName;

	private boolean autodetectUserTransaction = true;

	private boolean cacheUserTransaction = true;

	private boolean userTransactionObtainedFromJndi = false;

	private transient TransactionManager transactionManager;

	private String transactionManagerName;

	private boolean autodetectTransactionManager = true;

	private String transactionSynchronizationRegistryName;

	private transient Object transactionSynchronizationRegistry;

	private boolean allowCustomIsolationLevels = false;


	/**
	 * Create a new JtaTransactionManager instance, to be configured as bean.
	 * Invoke {@code afterPropertiesSet} to activate the configuration.
	 * @see #setUserTransactionName
	 * @see #setUserTransaction
	 * @see #setTransactionManagerName
	 * @see #setTransactionManager
	 * @see #afterPropertiesSet()
	 */
	public JtaTransactionManager() {
		setNestedTransactionAllowed(true);
	}

	/**
	 * Create a new JtaTransactionManager instance.
	 * @param userTransaction the JTA UserTransaction to use as direct reference
	 */
	public JtaTransactionManager(UserTransaction userTransaction) {
		this();
		Assert.notNull(userTransaction, "UserTransaction must not be null");
		this.userTransaction = userTransaction;
	}

	/**
	 * Create a new JtaTransactionManager instance.
	 * @param userTransaction the JTA UserTransaction to use as direct reference
	 * @param transactionManager the JTA TransactionManager to use as direct reference
	 */
	public JtaTransactionManager(UserTransaction userTransaction, TransactionManager transactionManager) {
		this();
		Assert.notNull(userTransaction, "UserTransaction must not be null");
		Assert.notNull(transactionManager, "TransactionManager must not be null");
		this.userTransaction = userTransaction;
		this.transactionManager = transactionManager;
	}

	/**
	 * Create a new JtaTransactionManager instance.
	 * @param transactionManager the JTA TransactionManager to use as direct reference
	 */
	public JtaTransactionManager(TransactionManager transactionManager) {
		this();
		Assert.notNull(transactionManager, "TransactionManager must not be null");
		this.transactionManager = transactionManager;
		this.userTransaction = buildUserTransaction(transactionManager);
	}


	/**
	 * Set the JndiTemplate to use for JNDI lookups.
	 * A default one is used if not set.
	 */
	public void setJndiTemplate(JndiTemplate jndiTemplate) {
		Assert.notNull(jndiTemplate, "JndiTemplate must not be null");
		this.jndiTemplate = jndiTemplate;
	}

	/**
	 * Return the JndiTemplate used for JNDI lookups.
	 */
	public JndiTemplate getJndiTemplate() {
		return this.jndiTemplate;
	}

	/**
	 * Set the JNDI environment to use for JNDI lookups.
	 * Creates a JndiTemplate with the given environment settings.
	 * @see #setJndiTemplate
	 */
	public void setJndiEnvironment(Properties jndiEnvironment) {
		this.jndiTemplate = new JndiTemplate(jndiEnvironment);
	}

	/**
	 * Return the JNDI environment to use for JNDI lookups.
	 */
	public Properties getJndiEnvironment() {
		return this.jndiTemplate.getEnvironment();
	}


	/**
	 * Set the JTA UserTransaction to use as direct reference.
	 * <p>Typically just used for local JTA setups; in a Java EE environment,
	 * the UserTransaction will always be fetched from JNDI.
	 * @see #setUserTransactionName
	 * @see #setAutodetectUserTransaction
	 */
	public void setUserTransaction(UserTransaction userTransaction) {
		this.userTransaction = userTransaction;
	}

	/**
	 * Return the JTA UserTransaction that this transaction manager uses.
	 */
	public UserTransaction getUserTransaction() {
		return this.userTransaction;
	}

	/**
	 * Set the JNDI name of the JTA UserTransaction.
	 * <p>Note that the UserTransaction will be autodetected at the Java EE
	 * default location "java:comp/UserTransaction" if not specified explicitly.
	 * @see #DEFAULT_USER_TRANSACTION_NAME
	 * @see #setUserTransaction
	 * @see #setAutodetectUserTransaction
	 */
	public void setUserTransactionName(String userTransactionName) {
		this.userTransactionName = userTransactionName;
	}

	/**
	 * Set whether to autodetect the JTA UserTransaction at its default
	 * JNDI location "java:comp/UserTransaction", as specified by Java EE.
	 * Will proceed without UserTransaction if none found.
	 * <p>Default is "true", autodetecting the UserTransaction unless
	 * it has been specified explicitly. Turn this flag off to allow for
	 * JtaTransactionManager operating against the TransactionManager only,
	 * despite a default UserTransaction being available.
	 * @see #DEFAULT_USER_TRANSACTION_NAME
	 */
	public void setAutodetectUserTransaction(boolean autodetectUserTransaction) {
		this.autodetectUserTransaction = autodetectUserTransaction;
	}

	/**
	 * Set whether to cache the JTA UserTransaction object fetched from JNDI.
	 * <p>Default is "true": UserTransaction lookup will only happen at startup,
	 * reusing the same UserTransaction handle for all transactions of all threads.
	 * This is the most efficient choice for all application servers that provide
	 * a shared UserTransaction object (the typical case).
	 * <p>Turn this flag off to enforce a fresh lookup of the UserTransaction
	 * for every transaction. This is only necessary for application servers
	 * that return a new UserTransaction for every transaction, keeping state
	 * tied to the UserTransaction object itself rather than the current thread.
	 * @see #setUserTransactionName
	 */
	public void setCacheUserTransaction(boolean cacheUserTransaction) {
		this.cacheUserTransaction = cacheUserTransaction;
	}

	/**
	 * Set the JTA TransactionManager to use as direct reference.
	 * <p>A TransactionManager is necessary for suspending and resuming transactions,
	 * as this not supported by the UserTransaction interface.
	 * <p>Note that the TransactionManager will be autodetected if the JTA
	 * UserTransaction object implements the JTA TransactionManager interface too,
	 * as well as autodetected at various well-known fallback JNDI locations.
	 * @see #setTransactionManagerName
	 * @see #setAutodetectTransactionManager
	 */
	public void setTransactionManager(TransactionManager transactionManager) {
		this.transactionManager = transactionManager;
	}

	/**
	 * Return the JTA TransactionManager that this transaction manager uses.
	 */
	public TransactionManager getTransactionManager() {
		return this.transactionManager;
	}

	/**
	 * Set the JNDI name of the JTA TransactionManager.
	 * <p>A TransactionManager is necessary for suspending and resuming transactions,
	 * as this not supported by the UserTransaction interface.
	 * <p>Note that the TransactionManager will be autodetected if the JTA
	 * UserTransaction object implements the JTA TransactionManager interface too,
	 * as well as autodetected at various well-known fallback JNDI locations.
	 * @see #setTransactionManager
	 * @see #setAutodetectTransactionManager
	 */
	public void setTransactionManagerName(String transactionManagerName) {
		this.transactionManagerName = transactionManagerName;
	}

	/**
	 * Set whether to autodetect a JTA UserTransaction object that implements
	 * the JTA TransactionManager interface too (i.e. the JNDI location for the
	 * TransactionManager is "java:comp/UserTransaction", same as for the UserTransaction).
	 * Also checks the fallback JNDI locations "java:comp/TransactionManager" and
	 * "java:/TransactionManager". Will proceed without TransactionManager if none found.
	 * <p>Default is "true", autodetecting the TransactionManager unless it has been
	 * specified explicitly. Can be turned off to deliberately ignore an available
	 * TransactionManager, for example when there are known issues with suspend/resume
	 * and any attempt to use REQUIRES_NEW or NOT_SUPPORTED should fail fast.
	 * @see #FALLBACK_TRANSACTION_MANAGER_NAMES
	 */
	public void setAutodetectTransactionManager(boolean autodetectTransactionManager) {
		this.autodetectTransactionManager = autodetectTransactionManager;
	}

	/**
	 * Set the JNDI name of the JTA 1.1 TransactionSynchronizationRegistry.
	 * <p>Note that the TransactionSynchronizationRegistry will be autodetected
	 * at the Java EE 5 default location "java:comp/TransactionSynchronizationRegistry"
	 * if not specified explicitly.
	 * @see #DEFAULT_TRANSACTION_SYNCHRONIZATION_REGISTRY_NAME
	 */
	public void setTransactionSynchronizationRegistryName(String transactionSynchronizationRegistryName) {
		this.transactionSynchronizationRegistryName = transactionSynchronizationRegistryName;
	}

	/**
	 * Set whether to allow custom isolation levels to be specified.
	 * <p>Default is "false", throwing an exception if a non-default isolation level
	 * is specified for a transaction. Turn this flag on if affected resource adapters
	 * check the thread-bound transaction context and apply the specified isolation
	 * levels individually (e.g. through an IsolationLevelDataSourceAdapter).
	 * @see org.springframework.jdbc.datasource.IsolationLevelDataSourceAdapter
	 * @see org.springframework.jdbc.datasource.lookup.IsolationLevelDataSourceRouter
	 */
	public void setAllowCustomIsolationLevels(boolean allowCustomIsolationLevels) {
		this.allowCustomIsolationLevels = allowCustomIsolationLevels;
	}


	/**
	 * Initialize the UserTransaction as well as the TransactionManager handle.
	 * @see #initUserTransactionAndTransactionManager()
	 */
	public void afterPropertiesSet() throws TransactionSystemException {
		initUserTransactionAndTransactionManager();
		checkUserTransactionAndTransactionManager();
		initTransactionSynchronizationRegistry();
	}

	/**
	 * Initialize the UserTransaction as well as the TransactionManager handle.
	 * @throws TransactionSystemException if initialization failed
	 */
	protected void initUserTransactionAndTransactionManager() throws TransactionSystemException {
		// Fetch JTA UserTransaction from JNDI, if necessary.
		if (this.userTransaction == null) {
			if (StringUtils.hasLength(this.userTransactionName)) {
				this.userTransaction = lookupUserTransaction(this.userTransactionName);
				this.userTransactionObtainedFromJndi = true;
			}
			else {
				this.userTransaction = retrieveUserTransaction();
			}
		}

		// Fetch JTA TransactionManager from JNDI, if necessary.
		if (this.transactionManager == null) {
			if (StringUtils.hasLength(this.transactionManagerName)) {
				this.transactionManager = lookupTransactionManager(this.transactionManagerName);
			}
			else {
				this.transactionManager = retrieveTransactionManager();
			}
		}

		// Autodetect UserTransaction at its default JNDI location.
		if (this.userTransaction == null && this.autodetectUserTransaction) {
			this.userTransaction = findUserTransaction();
		}

		// Autodetect UserTransaction object that implements TransactionManager,
		// and check fallback JNDI locations else.
		if (this.transactionManager == null && this.autodetectTransactionManager) {
			this.transactionManager = findTransactionManager(this.userTransaction);
		}

		// If only JTA TransactionManager specified, create UserTransaction handle for it.
		if (this.userTransaction == null && this.transactionManager != null) {
			this.userTransaction = buildUserTransaction(this.transactionManager);
		}
	}

	/**
	 * Check the UserTransaction as well as the TransactionManager handle,
	 * assuming standard JTA requirements.
	 * @throws IllegalStateException if no sufficient handles are available
	 */
	protected void checkUserTransactionAndTransactionManager() throws IllegalStateException {
		// We at least need the JTA UserTransaction.
		if (this.userTransaction != null) {
			if (logger.isInfoEnabled()) {
				logger.info("Using JTA UserTransaction: " + this.userTransaction);
			}
		}
		else {
			throw new IllegalStateException("No JTA UserTransaction available - specify either " +
					"'userTransaction' or 'userTransactionName' or 'transactionManager' or 'transactionManagerName'");
		}

		// For transaction suspension, the JTA TransactionManager is necessary too.
		if (this.transactionManager != null) {
			if (logger.isInfoEnabled()) {
				logger.info("Using JTA TransactionManager: " + this.transactionManager);
			}
		}
		else {
			logger.warn("No JTA TransactionManager found: transaction suspension not available");
		}
	}

	/**
	 * Initialize the JTA 1.1 TransactionSynchronizationRegistry, if available.
	 * <p>To be called after {@link #initUserTransactionAndTransactionManager()},
	 * since it may check the UserTransaction and TransactionManager handles.
	 * @throws TransactionSystemException if initialization failed
	 */
	protected void initTransactionSynchronizationRegistry() {
		if (StringUtils.hasLength(this.transactionSynchronizationRegistryName)) {
			this.transactionSynchronizationRegistry =
					lookupTransactionSynchronizationRegistry(this.transactionSynchronizationRegistryName);
		}
		else {
			this.transactionSynchronizationRegistry = retrieveTransactionSynchronizationRegistry();
			if (this.transactionSynchronizationRegistry == null) {
				this.transactionSynchronizationRegistry =
						findTransactionSynchronizationRegistry(this.userTransaction, this.transactionManager);
			}
		}

		if (this.transactionSynchronizationRegistry != null) {
			if (logger.isInfoEnabled()) {
				logger.info("Using JTA TransactionSynchronizationRegistry: " + this.transactionSynchronizationRegistry);
			}
		}
	}


	/**
	 * Build a UserTransaction handle based on the given TransactionManager.
	 * @param transactionManager the TransactionManager
	 * @return a corresponding UserTransaction handle
	 */
	protected UserTransaction buildUserTransaction(TransactionManager transactionManager) {
		if (transactionManager instanceof UserTransaction) {
			return (UserTransaction) transactionManager;
		}
		else {
			return new UserTransactionAdapter(transactionManager);
		}
	}

	/**
	 * Look up the JTA UserTransaction in JNDI via the configured name.
	 * <p>Called by {@code afterPropertiesSet} if no direct UserTransaction reference was set.
	 * Can be overridden in subclasses to provide a different UserTransaction object.
	 * @param userTransactionName the JNDI name of the UserTransaction
	 * @return the UserTransaction object
	 * @throws TransactionSystemException if the JNDI lookup failed
	 * @see #setJndiTemplate
	 * @see #setUserTransactionName
	 */
	protected UserTransaction lookupUserTransaction(String userTransactionName)
			throws TransactionSystemException {
		try {
			if (logger.isDebugEnabled()) {
				logger.debug("Retrieving JTA UserTransaction from JNDI location [" + userTransactionName + "]");
			}
			return getJndiTemplate().lookup(userTransactionName, UserTransaction.class);
		}
		catch (NamingException ex) {
			throw new TransactionSystemException(
					"JTA UserTransaction is not available at JNDI location [" + userTransactionName + "]", ex);
		}
	}

	/**
	 * Look up the JTA TransactionManager in JNDI via the configured name.
	 * <p>Called by {@code afterPropertiesSet} if no direct TransactionManager reference was set.
	 * Can be overridden in subclasses to provide a different TransactionManager object.
	 * @param transactionManagerName the JNDI name of the TransactionManager
	 * @return the UserTransaction object
	 * @throws TransactionSystemException if the JNDI lookup failed
	 * @see #setJndiTemplate
	 * @see #setTransactionManagerName
	 */
	protected TransactionManager lookupTransactionManager(String transactionManagerName)
			throws TransactionSystemException {
		try {
			if (logger.isDebugEnabled()) {
				logger.debug("Retrieving JTA TransactionManager from JNDI location [" + transactionManagerName + "]");
			}
			return getJndiTemplate().lookup(transactionManagerName, TransactionManager.class);
		}
		catch (NamingException ex) {
			throw new TransactionSystemException(
					"JTA TransactionManager is not available at JNDI location [" + transactionManagerName + "]", ex);
		}
	}

	/**
	 * Look up the JTA 1.1 TransactionSynchronizationRegistry in JNDI via the configured name.
	 * <p>Can be overridden in subclasses to provide a different TransactionManager object.
	 * @param registryName the JNDI name of the
	 * TransactionSynchronizationRegistry
	 * @return the TransactionSynchronizationRegistry object
	 * @throws TransactionSystemException if the JNDI lookup failed
	 * @see #setJndiTemplate
	 * @see #setTransactionSynchronizationRegistryName
	 */
	protected Object lookupTransactionSynchronizationRegistry(String registryName) throws TransactionSystemException {
		if (transactionSynchronizationRegistryClass == null) {
			throw new TransactionSystemException(
					"JTA 1.1 [" + TRANSACTION_SYNCHRONIZATION_REGISTRY_CLASS_NAME + "] API not available");
		}
		try {
			if (logger.isDebugEnabled()) {
				logger.debug("Retrieving JTA TransactionSynchronizationRegistry from JNDI location [" + registryName + "]");
			}
			return getJndiTemplate().lookup(registryName, transactionSynchronizationRegistryClass);
		}
		catch (NamingException ex) {
			throw new TransactionSystemException(
					"JTA TransactionSynchronizationRegistry is not available at JNDI location [" + registryName + "]", ex);
		}
	}

	/**
	 * Allows subclasses to retrieve the JTA UserTransaction in a vendor-specific manner.
	 * Only called if no "userTransaction" or "userTransactionName" specified.
	 * <p>The default implementation simply returns {@code null}.
	 * @return the JTA UserTransaction handle to use, or {@code null} if none found
	 * @throws TransactionSystemException in case of errors
	 * @see #setUserTransaction
	 * @see #setUserTransactionName
	 */
	protected UserTransaction retrieveUserTransaction() throws TransactionSystemException {
		return null;
	}

	/**
	 * Allows subclasses to retrieve the JTA TransactionManager in a vendor-specific manner.
	 * Only called if no "transactionManager" or "transactionManagerName" specified.
	 * <p>The default implementation simply returns {@code null}.
	 * @return the JTA TransactionManager handle to use, or {@code null} if none found
	 * @throws TransactionSystemException in case of errors
	 * @see #setTransactionManager
	 * @see #setTransactionManagerName
	 */
	protected TransactionManager retrieveTransactionManager() throws TransactionSystemException {
		return null;
	}

	/**
	 * Allows subclasses to retrieve the JTA 1.1 TransactionSynchronizationRegistry
	 * in a vendor-specific manner.
	 * <p>The default implementation simply returns {@code null}.
	 * @return the JTA TransactionSynchronizationRegistry handle to use,
	 * or {@code null} if none found
	 * @throws TransactionSystemException in case of errors
	 */
	protected Object retrieveTransactionSynchronizationRegistry() throws TransactionSystemException {
		return null;
	}

	/**
	 * Find the JTA UserTransaction through a default JNDI lookup:
	 * "java:comp/UserTransaction".
	 * @return the JTA UserTransaction reference, or {@code null} if not found
	 * @see #DEFAULT_USER_TRANSACTION_NAME
	 */
	protected UserTransaction findUserTransaction() {
		String jndiName = DEFAULT_USER_TRANSACTION_NAME;
		try {
			UserTransaction ut = getJndiTemplate().lookup(jndiName, UserTransaction.class);
			if (logger.isDebugEnabled()) {
				logger.debug("JTA UserTransaction found at default JNDI location [" + jndiName + "]");
			}
			this.userTransactionObtainedFromJndi = true;
			return ut;
		}
		catch (NamingException ex) {
			if (logger.isDebugEnabled()) {
				logger.debug("No JTA UserTransaction found at default JNDI location [" + jndiName + "]", ex);
			}
			return null;
		}
	}

	/**
	 * Find the JTA TransactionManager through autodetection: checking whether the
	 * UserTransaction object implements the TransactionManager, and checking the
	 * fallback JNDI locations.
	 * @param ut the JTA UserTransaction object
	 * @return the JTA TransactionManager reference, or {@code null} if not found
	 * @see #FALLBACK_TRANSACTION_MANAGER_NAMES
	 */
	protected TransactionManager findTransactionManager(UserTransaction ut) {
		if (ut instanceof TransactionManager) {
			if (logger.isDebugEnabled()) {
				logger.debug("JTA UserTransaction object [" + ut + "] implements TransactionManager");
			}
			return (TransactionManager) ut;
		}

		// Check fallback JNDI locations.
		for (String jndiName : FALLBACK_TRANSACTION_MANAGER_NAMES) {
			try {
				TransactionManager tm = getJndiTemplate().lookup(jndiName, TransactionManager.class);
				if (logger.isDebugEnabled()) {
					logger.debug("JTA TransactionManager found at fallback JNDI location [" + jndiName + "]");
				}
				return tm;
			}
			catch (NamingException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug("No JTA TransactionManager found at fallback JNDI location [" + jndiName + "]", ex);
				}
			}
		}

		// OK, so no JTA TransactionManager is available...
		return null;
	}

	/**
	 * Find the JTA 1.1 TransactionSynchronizationRegistry through autodetection:
	 * checking whether the UserTransaction object or TransactionManager object
	 * implements it, and checking Java EE 5's standard JNDI location.
	 * <p>The default implementation simply returns {@code null}.
	 * @param ut the JTA UserTransaction object
	 * @param tm the JTA TransactionManager object
	 * @return the JTA TransactionSynchronizationRegistry handle to use,
	 * or {@code null} if none found
	 * @throws TransactionSystemException in case of errors
	 */
	protected Object findTransactionSynchronizationRegistry(UserTransaction ut, TransactionManager tm)
			throws TransactionSystemException {

		if (transactionSynchronizationRegistryClass == null) {
			// JTA 1.1 API not present - skip.
			if (logger.isDebugEnabled()) {
				logger.debug("JTA 1.1 [" + TRANSACTION_SYNCHRONIZATION_REGISTRY_CLASS_NAME + "] API not available");
			}
			return null;
		}

		// If we came here, we might be on Java EE 5, since the JTA 1.1 API is present.
		if (this.userTransactionObtainedFromJndi) {
			// UserTransaction has already been obtained from JNDI, so the
			// TransactionSynchronizationRegistry probably sits there as well.
			String jndiName = DEFAULT_TRANSACTION_SYNCHRONIZATION_REGISTRY_NAME;
			try {
				Object tsr = getJndiTemplate().lookup(jndiName, transactionSynchronizationRegistryClass);
				if (logger.isDebugEnabled()) {
					logger.debug("JTA TransactionSynchronizationRegistry found at default JNDI location [" + jndiName + "]");
				}
				return tsr;
			}
			catch (NamingException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug(
							"No JTA TransactionSynchronizationRegistry found at default JNDI location [" + jndiName + "]", ex);
				}
			}
		}
		// Check whether the UserTransaction or TransactionManager implements it...
		if (transactionSynchronizationRegistryClass.isInstance(ut)) {
			return ut;
		}
		if (transactionSynchronizationRegistryClass.isInstance(tm)) {
			return tm;
		}
		// OK, so no JTA 1.1 TransactionSynchronizationRegistry is available,
		// despite the API being present...
		return null;
	}


	/**
	 * This implementation returns a JtaTransactionObject instance for the
	 * JTA UserTransaction.
	 * <p>The UserTransaction object will either be looked up freshly for the
	 * current transaction, or the cached one looked up at startup will be used.
	 * The latter is the default: Most application servers use a shared singleton
	 * UserTransaction that can be cached. Turn off the "cacheUserTransaction"
	 * flag to enforce a fresh lookup for every transaction.
	 * @see #setCacheUserTransaction
	 */
	@Override
	protected Object doGetTransaction() {
		UserTransaction ut = getUserTransaction();
		if (ut == null) {
			throw new CannotCreateTransactionException("No JTA UserTransaction available - " +
					"programmatic PlatformTransactionManager.getTransaction usage not supported");
		}
		if (!this.cacheUserTransaction) {
			ut = lookupUserTransaction(
					this.userTransactionName != null ? this.userTransactionName : DEFAULT_USER_TRANSACTION_NAME);
		}
		return doGetJtaTransaction(ut);
	}

	/**
	 * Get a JTA transaction object for the given current UserTransaction.
	 * <p>Subclasses can override this to provide a JtaTransactionObject
	 * subclass, for example holding some additional JTA handle needed.
	 * @param ut the UserTransaction handle to use for the current transaction
	 * @return the JtaTransactionObject holding the UserTransaction
	 */
	protected JtaTransactionObject doGetJtaTransaction(UserTransaction ut) {
		return new JtaTransactionObject(ut);
	}

	@Override
	protected boolean isExistingTransaction(Object transaction) {
		JtaTransactionObject txObject = (JtaTransactionObject) transaction;
		try {
			return (txObject.getUserTransaction().getStatus() != Status.STATUS_NO_TRANSACTION);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on getStatus", ex);
		}
	}

	/**
	 * This implementation returns false to cause a further invocation
	 * of doBegin despite an already existing transaction.
	 * <p>JTA implementations might support nested transactions via further
	 * {@code UserTransaction.begin()} invocations, but never support savepoints.
	 * @see #doBegin
	 * @see javax.transaction.UserTransaction#begin()
	 */
	@Override
	protected boolean useSavepointForNestedTransaction() {
		return false;
	}


	@Override
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		JtaTransactionObject txObject = (JtaTransactionObject) transaction;
		try {
			doJtaBegin(txObject, definition);
		}
		catch (NotSupportedException ex) {
			// assume nested transaction not supported
			throw new NestedTransactionNotSupportedException(
				"JTA implementation does not support nested transactions", ex);
		}
		catch (UnsupportedOperationException ex) {
			// assume nested transaction not supported
			throw new NestedTransactionNotSupportedException(
				"JTA implementation does not support nested transactions", ex);
		}
		catch (SystemException ex) {
			throw new CannotCreateTransactionException("JTA failure on begin", ex);
		}
	}

	/**
	 * Perform a JTA begin on the JTA UserTransaction or TransactionManager.
	 * <p>This implementation only supports standard JTA functionality:
	 * that is, no per-transaction isolation levels and no transaction names.
	 * Can be overridden in subclasses, for specific JTA implementations.
	 * <p>Calls {@code applyIsolationLevel} and {@code applyTimeout}
	 * before invoking the UserTransaction's {@code begin} method.
	 * @param txObject the JtaTransactionObject containing the UserTransaction
	 * @param definition TransactionDefinition instance, describing propagation
	 * behavior, isolation level, read-only flag, timeout, and transaction name
	 * @throws NotSupportedException if thrown by JTA methods
	 * @throws SystemException if thrown by JTA methods
	 * @see #getUserTransaction
	 * @see #getTransactionManager
	 * @see #applyIsolationLevel
	 * @see #applyTimeout
	 * @see JtaTransactionObject#getUserTransaction()
	 * @see javax.transaction.UserTransaction#setTransactionTimeout
	 * @see javax.transaction.UserTransaction#begin
	 */
	protected void doJtaBegin(JtaTransactionObject txObject, TransactionDefinition definition)
			throws NotSupportedException, SystemException {

		applyIsolationLevel(txObject, definition.getIsolationLevel());
		int timeout = determineTimeout(definition);
		applyTimeout(txObject, timeout);
		txObject.getUserTransaction().begin();
	}

	/**
	 * Apply the given transaction isolation level. The default implementation
	 * will throw an exception for any level other than ISOLATION_DEFAULT.
	 * <p>To be overridden in subclasses for specific JTA implementations,
	 * as alternative to overriding the full {@link #doJtaBegin} method.
	 * @param txObject the JtaTransactionObject containing the UserTransaction
	 * @param isolationLevel isolation level taken from transaction definition
	 * @throws InvalidIsolationLevelException if the given isolation level
	 * cannot be applied
	 * @throws SystemException if thrown by the JTA implementation
	 * @see #doJtaBegin
	 * @see JtaTransactionObject#getUserTransaction()
	 * @see #getTransactionManager()
	 */
	protected void applyIsolationLevel(JtaTransactionObject txObject, int isolationLevel)
			throws InvalidIsolationLevelException, SystemException {

		if (!this.allowCustomIsolationLevels && isolationLevel != TransactionDefinition.ISOLATION_DEFAULT) {
			throw new InvalidIsolationLevelException(
				"JtaTransactionManager does not support custom isolation levels by default - " +
				"switch 'allowCustomIsolationLevels' to 'true'");
		}
	}

	/**
	 * Apply the given transaction timeout. The default implementation will call
	 * {@code UserTransaction.setTransactionTimeout} for a non-default timeout value.
	 * @param txObject the JtaTransactionObject containing the UserTransaction
	 * @param timeout timeout value taken from transaction definition
	 * @throws SystemException if thrown by the JTA implementation
	 * @see #doJtaBegin
	 * @see JtaTransactionObject#getUserTransaction()
	 * @see javax.transaction.UserTransaction#setTransactionTimeout(int)
	 */
	protected void applyTimeout(JtaTransactionObject txObject, int timeout) throws SystemException {
		if (timeout > TransactionDefinition.TIMEOUT_DEFAULT) {
			txObject.getUserTransaction().setTransactionTimeout(timeout);
		}
	}


	@Override
	protected Object doSuspend(Object transaction) {
		JtaTransactionObject txObject = (JtaTransactionObject) transaction;
		try {
			return doJtaSuspend(txObject);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on suspend", ex);
		}
	}

	/**
	 * Perform a JTA suspend on the JTA TransactionManager.
	 * <p>Can be overridden in subclasses, for specific JTA implementations.
	 * @param txObject the JtaTransactionObject containing the UserTransaction
	 * @return the suspended JTA Transaction object
	 * @throws SystemException if thrown by JTA methods
	 * @see #getTransactionManager()
	 * @see javax.transaction.TransactionManager#suspend()
	 */
	protected Object doJtaSuspend(JtaTransactionObject txObject) throws SystemException {
		if (getTransactionManager() == null) {
			throw new TransactionSuspensionNotSupportedException(
					"JtaTransactionManager needs a JTA TransactionManager for suspending a transaction: " +
					"specify the 'transactionManager' or 'transactionManagerName' property");
		}
		return getTransactionManager().suspend();
	}

	@Override
	protected void doResume(Object transaction, Object suspendedResources) {
		JtaTransactionObject txObject = (JtaTransactionObject) transaction;
		try {
			doJtaResume(txObject, suspendedResources);
		}
		catch (InvalidTransactionException ex) {
			throw new IllegalTransactionStateException("Tried to resume invalid JTA transaction", ex);
		}
		catch (IllegalStateException ex) {
			throw new TransactionSystemException("Unexpected internal transaction state", ex);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on resume", ex);
		}
	}

	/**
	 * Perform a JTA resume on the JTA TransactionManager.
	 * <p>Can be overridden in subclasses, for specific JTA implementations.
	 * @param txObject the JtaTransactionObject containing the UserTransaction
	 * @param suspendedTransaction the suspended JTA Transaction object
	 * @throws InvalidTransactionException if thrown by JTA methods
	 * @throws SystemException if thrown by JTA methods
	 * @see #getTransactionManager()
	 * @see javax.transaction.TransactionManager#resume(javax.transaction.Transaction)
	 */
	protected void doJtaResume(JtaTransactionObject txObject, Object suspendedTransaction)
		throws InvalidTransactionException, SystemException {

		if (getTransactionManager() == null) {
			throw new TransactionSuspensionNotSupportedException(
					"JtaTransactionManager needs a JTA TransactionManager for suspending a transaction: " +
					"specify the 'transactionManager' or 'transactionManagerName' property");
		}
		getTransactionManager().resume((Transaction) suspendedTransaction);
	}


	/**
	 * This implementation returns "true": a JTA commit will properly handle
	 * transactions that have been marked rollback-only at a global level.
	 */
	@Override
	protected boolean shouldCommitOnGlobalRollbackOnly() {
		return true;
	}

	@Override
	protected void doCommit(DefaultTransactionStatus status) {
		JtaTransactionObject txObject = (JtaTransactionObject) status.getTransaction();
		try {
			int jtaStatus = txObject.getUserTransaction().getStatus();
			if (jtaStatus == Status.STATUS_NO_TRANSACTION) {
				// Should never happen... would have thrown an exception before
				// and as a consequence led to a rollback, not to a commit call.
				// In any case, the transaction is already fully cleaned up.
				throw new UnexpectedRollbackException("JTA transaction already completed - probably rolled back");
			}
			if (jtaStatus == Status.STATUS_ROLLEDBACK) {
				// Only really happens on JBoss 4.2 in case of an early timeout...
				// Explicit rollback call necessary to clean up the transaction.
				// IllegalStateException expected on JBoss; call still necessary.
				try {
					txObject.getUserTransaction().rollback();
				}
				catch (IllegalStateException ex) {
					if (logger.isDebugEnabled()) {
						logger.debug("Rollback failure with transaction already marked as rolled back: " + ex);
					}
				}
				throw new UnexpectedRollbackException("JTA transaction already rolled back (probably due to a timeout)");
			}
			txObject.getUserTransaction().commit();
		}
		catch (RollbackException ex) {
			throw new UnexpectedRollbackException(
					"JTA transaction unexpectedly rolled back (maybe due to a timeout)", ex);
		}
		catch (HeuristicMixedException ex) {
			throw new HeuristicCompletionException(HeuristicCompletionException.STATE_MIXED, ex);
		}
		catch (HeuristicRollbackException ex) {
			throw new HeuristicCompletionException(HeuristicCompletionException.STATE_ROLLED_BACK, ex);
		}
		catch (IllegalStateException ex) {
			throw new TransactionSystemException("Unexpected internal transaction state", ex);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on commit", ex);
		}
	}

	@Override
	protected void doRollback(DefaultTransactionStatus status) {
		JtaTransactionObject txObject = (JtaTransactionObject) status.getTransaction();
		try {
			int jtaStatus = txObject.getUserTransaction().getStatus();
			if (jtaStatus != Status.STATUS_NO_TRANSACTION) {
				try {
					txObject.getUserTransaction().rollback();
				}
				catch (IllegalStateException ex) {
					if (jtaStatus == Status.STATUS_ROLLEDBACK) {
						// Only really happens on JBoss 4.2 in case of an early timeout...
						if (logger.isDebugEnabled()) {
							logger.debug("Rollback failure with transaction already marked as rolled back: " + ex);
						}
					}
					else {
						throw new TransactionSystemException("Unexpected internal transaction state", ex);
					}
				}
			}
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on rollback", ex);
		}
	}

	@Override
	protected void doSetRollbackOnly(DefaultTransactionStatus status) {
		JtaTransactionObject txObject = (JtaTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Setting JTA transaction rollback-only");
		}
		try {
			int jtaStatus = txObject.getUserTransaction().getStatus();
			if (jtaStatus != Status.STATUS_NO_TRANSACTION && jtaStatus != Status.STATUS_ROLLEDBACK) {
				txObject.getUserTransaction().setRollbackOnly();
			}
		}
		catch (IllegalStateException ex) {
			throw new TransactionSystemException("Unexpected internal transaction state", ex);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on setRollbackOnly", ex);
		}
	}


	@Override
	protected void registerAfterCompletionWithExistingTransaction(
			Object transaction, List<TransactionSynchronization> synchronizations) {

		JtaTransactionObject txObject = (JtaTransactionObject) transaction;
		logger.debug("Registering after-completion synchronization with existing JTA transaction");
		try {
			doRegisterAfterCompletionWithJtaTransaction(txObject, synchronizations);
		}
		catch (SystemException ex) {
			throw new TransactionSystemException("JTA failure on registerSynchronization", ex);
		}
		catch (Exception ex) {
			// Note: JBoss throws plain RuntimeException with RollbackException as cause.
			if (ex instanceof RollbackException || ex.getCause() instanceof RollbackException) {
				logger.debug("Participating in existing JTA transaction that has been marked for rollback: " +
						"cannot register Spring after-completion callbacks with outer JTA transaction - " +
						"immediately performing Spring after-completion callbacks with outcome status 'rollback'. " +
						"Original exception: " + ex);
				invokeAfterCompletion(synchronizations, TransactionSynchronization.STATUS_ROLLED_BACK);
			}
			else {
				logger.debug("Participating in existing JTA transaction, but unexpected internal transaction " +
						"state encountered: cannot register Spring after-completion callbacks with outer JTA " +
						"transaction - processing Spring after-completion callbacks with outcome status 'unknown'" +
						"Original exception: " + ex);
				invokeAfterCompletion(synchronizations, TransactionSynchronization.STATUS_UNKNOWN);
			}
		}
	}

	/**
	 * Register a JTA synchronization on the JTA TransactionManager, for calling
	 * {@code afterCompletion} on the given Spring TransactionSynchronizations.
	 * <p>The default implementation registers the synchronizations on the
	 * JTA 1.1 TransactionSynchronizationRegistry, if available, or on the
	 * JTA TransactionManager's current Transaction - again, if available.
	 * If none of the two is available, a warning will be logged.
	 * <p>Can be overridden in subclasses, for specific JTA implementations.
	 * @param txObject the current transaction object
	 * @param synchronizations List of TransactionSynchronization objects
	 * @throws RollbackException if thrown by JTA methods
	 * @throws SystemException if thrown by JTA methods
	 * @see #getTransactionManager()
	 * @see javax.transaction.Transaction#registerSynchronization
	 * @see javax.transaction.TransactionSynchronizationRegistry#registerInterposedSynchronization
	 */
	protected void doRegisterAfterCompletionWithJtaTransaction(
			JtaTransactionObject txObject, List<TransactionSynchronization> synchronizations)
			throws RollbackException, SystemException {

		int jtaStatus = txObject.getUserTransaction().getStatus();
		if (jtaStatus == Status.STATUS_NO_TRANSACTION) {
			throw new RollbackException("JTA transaction already completed - probably rolled back");
		}
		if (jtaStatus == Status.STATUS_ROLLEDBACK) {
			throw new RollbackException("JTA transaction already rolled back (probably due to a timeout)");
		}

		if (this.transactionSynchronizationRegistry != null) {
			// JTA 1.1 TransactionSynchronizationRegistry available - use it.
			new InterposedSynchronizationDelegate().registerInterposedSynchronization(
					new JtaAfterCompletionSynchronization(synchronizations));
		}

		else if (getTransactionManager() != null) {
			// At least the JTA TransactionManager available - use that one.
			Transaction transaction = getTransactionManager().getTransaction();
			if (transaction == null) {
				throw new IllegalStateException("No JTA Transaction available");
			}
			transaction.registerSynchronization(new JtaAfterCompletionSynchronization(synchronizations));
		}

		else {
			// No JTA TransactionManager available - log a warning.
			logger.warn("Participating in existing JTA transaction, but no JTA TransactionManager available: " +
					"cannot register Spring after-completion callbacks with outer JTA transaction - " +
					"processing Spring after-completion callbacks with outcome status 'unknown'");
			invokeAfterCompletion(synchronizations, TransactionSynchronization.STATUS_UNKNOWN);
		}
	}


	//---------------------------------------------------------------------
	// Implementation of TransactionFactory interface
	//---------------------------------------------------------------------

	public Transaction createTransaction(String name, int timeout) throws NotSupportedException, SystemException {
		TransactionManager tm = getTransactionManager();
		Assert.state(tm != null, "No JTA TransactionManager available");
		if (timeout >= 0) {
			tm.setTransactionTimeout(timeout);
		}
		tm.begin();
		return new ManagedTransactionAdapter(tm);
	}

	public boolean supportsResourceAdapterManagedTransactions() {
		return false;
	}


	//---------------------------------------------------------------------
	// Serialization support
	//---------------------------------------------------------------------

	private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
		// Rely on default serialization; just initialize state after deserialization.
		ois.defaultReadObject();

		// Create template for client-side JNDI lookup.
		this.jndiTemplate = new JndiTemplate();

		// Perform a fresh lookup for JTA handles.
		initUserTransactionAndTransactionManager();
		initTransactionSynchronizationRegistry();
	}


	/**
	 * Inner class to avoid a direct dependency on the JTA 1.1 API
	 * (javax.transaction.TransactionSynchronizationRegistry interface).
	 */
	private class InterposedSynchronizationDelegate {

		public void registerInterposedSynchronization(Synchronization synch) {
			((TransactionSynchronizationRegistry) transactionSynchronizationRegistry).registerInterposedSynchronization(synch);
		}
	}

}
