transactionsynchronizationmanager.java

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	}

	/**
	 * Activate transaction synchronization for the current thread.
	 * Called by a transaction manager on transaction begin.
	 * @throws IllegalStateException if synchronization is already active
	 */
	public static void initSynchronization() throws IllegalStateException {
		if (isSynchronizationActive()) {
			throw new IllegalStateException("Cannot activate transaction synchronization - already active");
		}
		logger.debug("Initializing transaction synchronization");
		synchronizations.set(new LinkedList());
	}

	/**
	 * Register a new transaction synchronization for the current thread.
	 * Typically called by resource management code.
	 * <p>Note that synchronizations can implement the
	 * {@link org.springframework.core.Ordered} interface.
	 * They will be executed in an order according to their order value (if any).
	 * @param synchronization the synchronization object to register
	 * @throws IllegalStateException if transaction synchronization is not active
	 * @see org.springframework.core.Ordered
	 */
	public static void registerSynchronization(TransactionSynchronization synchronization)
	    throws IllegalStateException {

		Assert.notNull(synchronization, "TransactionSynchronization must not be null");
		if (!isSynchronizationActive()) {
			throw new IllegalStateException("Transaction synchronization is not active");
		}
		List synchs = (List) synchronizations.get();
		synchs.add(synchronization);
	}

	/**
	 * Return an unmodifiable snapshot list of all registered synchronizations
	 * for the current thread.
	 * @return unmodifiable List of TransactionSynchronization instances
	 * @throws IllegalStateException if synchronization is not active
	 * @see TransactionSynchronization
	 */
	public static List getSynchronizations() throws IllegalStateException {
		if (!isSynchronizationActive()) {
			throw new IllegalStateException("Transaction synchronization is not active");
		}
		List synchs = (List) synchronizations.get();
		// Sort lazily here, not in registerSynchronization.
		Collections.sort(synchs, synchronizationComparator);
		// Return unmodifiable snapshot, to avoid ConcurrentModificationExceptions
		// while iterating and invoking synchronization callbacks that in turn
		// might register further synchronizations.
		return Collections.unmodifiableList(new ArrayList(synchs));
	}

	/**
	 * Deactivate transaction synchronization for the current thread.
	 * Called by the transaction manager on transaction cleanup.
	 * @throws IllegalStateException if synchronization is not active
	 */
	public static void clearSynchronization() throws IllegalStateException {
		if (!isSynchronizationActive()) {
			throw new IllegalStateException("Cannot deactivate transaction synchronization - not active");
		}
		logger.debug("Clearing transaction synchronization");
		synchronizations.set(null);
	}


	//-------------------------------------------------------------------------
	// Exposure of transaction characteristics
	//-------------------------------------------------------------------------

	/**
	 * Expose the name of the current transaction, if any.
	 * Called by the transaction manager on transaction begin and on cleanup.
	 * @param name the name of the transaction, or <code>null</code> to reset it
	 * @see org.springframework.transaction.TransactionDefinition#getName()
	 */
	public static void setCurrentTransactionName(String name) {
		currentTransactionName.set(name);
	}

	/**
	 * Return the name of the current transaction, or <code>null</code> if none set.
	 * To be called by resource management code for optimizations per use case,
	 * for example to optimize fetch strategies for specific named transactions.
	 * @see org.springframework.transaction.TransactionDefinition#getName()
	 */
	public static String getCurrentTransactionName() {
		return (String) currentTransactionName.get();
	}

	/**
	 * Expose a read-only flag for the current transaction.
	 * Called by the transaction manager on transaction begin and on cleanup.
	 * @param readOnly <code>true</code> to mark the current transaction
	 * as read-only; <code>false</code> to reset such a read-only marker
	 * @see org.springframework.transaction.TransactionDefinition#isReadOnly()
	 */
	public static void setCurrentTransactionReadOnly(boolean readOnly) {
		currentTransactionReadOnly.set(readOnly ? Boolean.TRUE : null);
	}

	/**
	 * Return whether the current transaction is marked as read-only.
	 * To be called by resource management code when preparing a newly
	 * created resource (for example, a Hibernate Session).
	 * <p>Note that transaction synchronizations receive the read-only flag
	 * as argument for the <code>beforeCommit</code> callback, to be able
	 * to suppress change detection on commit. The present method is meant
	 * to be used for earlier read-only checks, for example to set the
	 * flush mode of a Hibernate Session to "FlushMode.NEVER" upfront.
	 * @see org.springframework.transaction.TransactionDefinition#isReadOnly()
	 * @see TransactionSynchronization#beforeCommit(boolean)
	 * @see org.hibernate.Session#flush
	 * @see org.hibernate.Session#setFlushMode
	 * @see org.hibernate.FlushMode#NEVER
	 */
	public static boolean isCurrentTransactionReadOnly() {
		return (currentTransactionReadOnly.get() != null);
	}

	/**
	 * Expose an isolation level for the current transaction.
	 * Called by the transaction manager on transaction begin and on cleanup.
	 * @param isolationLevel the isolation level to expose, according to the
	 * JDBC Connection constants (equivalent to the corresponding Spring
	 * TransactionDefinition constants), or <code>null</code> to reset it
	 * @see java.sql.Connection#TRANSACTION_READ_UNCOMMITTED
	 * @see java.sql.Connection#TRANSACTION_READ_COMMITTED
	 * @see java.sql.Connection#TRANSACTION_REPEATABLE_READ
	 * @see java.sql.Connection#TRANSACTION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_UNCOMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_COMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_REPEATABLE_READ
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#getIsolationLevel()
	 */
	public static void setCurrentTransactionIsolationLevel(Integer isolationLevel) {
		currentTransactionIsolationLevel.set(isolationLevel);
	}

	/**
	 * Return the isolation level for the current transaction, if any.
	 * To be called by resource management code when preparing a newly
	 * created resource (for example, a JDBC Connection).
	 * @return the currently exposed isolation level, according to the
	 * JDBC Connection constants (equivalent to the corresponding Spring
	 * TransactionDefinition constants), or <code>null</code> if none
	 * @see java.sql.Connection#TRANSACTION_READ_UNCOMMITTED
	 * @see java.sql.Connection#TRANSACTION_READ_COMMITTED
	 * @see java.sql.Connection#TRANSACTION_REPEATABLE_READ
	 * @see java.sql.Connection#TRANSACTION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_UNCOMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_READ_COMMITTED
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_REPEATABLE_READ
	 * @see org.springframework.transaction.TransactionDefinition#ISOLATION_SERIALIZABLE
	 * @see org.springframework.transaction.TransactionDefinition#getIsolationLevel()
	 */
	public static Integer getCurrentTransactionIsolationLevel() {
		return (Integer) currentTransactionIsolationLevel.get();
	}

	/**
	 * Expose whether there currently is an actual transaction active.
	 * Called by the transaction manager on transaction begin and on cleanup.
	 * @param active <code>true</code> to mark the current thread as being associated
	 * with an actual transaction; <code>false</code> to reset that marker
	 */
	public static void setActualTransactionActive(boolean active) {
		actualTransactionActive.set(active ? Boolean.TRUE : null);
	}

	/**
	 * Return whether there currently is an actual transaction active.
	 * This indicates whether the current thread is associated with an actual
	 * transaction rather than just with active transaction synchronization.
	 * <p>To be called by resource management code that wants to discriminate
	 * between active transaction synchronization (with or without backing
	 * resource transaction; also on PROPAGATION_SUPPORTS) and an actual
	 * transaction being active (with backing resource transaction;
	 * on PROPAGATION_REQUIRES, PROPAGATION_REQUIRES_NEW, etc).
	 * @see #isSynchronizationActive()
	 */
	public static boolean isActualTransactionActive() {
		return (actualTransactionActive.get() != null);
	}


	/**
	 * Clear the entire transaction synchronization state for the current thread:
	 * registered synchronizations as well as the various transaction characteristics.
	 * @see #clearSynchronization()
	 * @see #setCurrentTransactionName
	 * @see #setCurrentTransactionReadOnly
	 * @see #setCurrentTransactionIsolationLevel
	 * @see #setActualTransactionActive
	 */
	public static void clear() {
		clearSynchronization();
		setCurrentTransactionName(null);
		setCurrentTransactionReadOnly(false);
		setCurrentTransactionIsolationLevel(null);
		setActualTransactionActive(false);
	}

}