datasourcetransactionmanager.java

spring的源代码

/*
 * Copyright 2002-2005 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.jdbc.datasource;

import java.sql.Connection;
import java.sql.SQLException;

import javax.sql.DataSource;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.transaction.CannotCreateTransactionException;
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.TransactionSynchronizationManager;

/**
 * PlatformTransactionManager implementation for a single JDBC DataSource.
 * Able to work in any environment with any JDBC driver, as long as the setup uses
 * a JDBC 2.0 Standard Extensions / JDBC 3.0 <code>javax.sql.DataSource</code>
 * as its Connection factory mechanism. Binds a JDBC Connection from the
 * specified DataSource to the thread, potentially allowing for one thread
 * Connection per DataSource.
 *
 * <p>Application code is required to retrieve the JDBC Connection via
 * <code>DataSourceUtils.getConnection(DataSource)</code> instead of J2EE's standard
 * <code>DataSource.getConnection()</code>. This is recommended anyway, as it throws
 * unchecked org.springframework.dao exceptions instead of checked SQLException.
 * All framework classes like JdbcTemplate use this strategy implicitly.
 * If not used with this transaction manager, the lookup strategy behaves exactly
 * like the common one - it can thus be used in any case.
 *
 * <p>Alternatively, you can also allow application code to work with the standard
 * J2EE lookup pattern <code>DataSource.getConnection()</code>, for example for
 * legacy code that is not aware of Spring at all. In that case, define a
 * TransactionAwareDataSourceProxy for your target DataSource, and pass that proxy
 * DataSource to your DAOs, which will automatically participate in Spring-managed
 * transactions through it. Note that DataSourceTransactionManager still needs to
 * be wired with the target DataSource, driving transactions for it.
 *
 * <p>Supports custom isolation levels, and timeouts that get applied as
 * appropriate JDBC statement timeouts. To support the latter, application code
 * must either use JdbcTemplate, call <code>DataSourceUtils.applyTransactionTimeout</code>
 * for each created statement, or go through a TransactionAwareDataSourceProxy
 * which will create timeout-aware Connections and Statements.
 *
 * <p>Consider defining a LazyConnectionDataSourceProxy for your target DataSource,
 * pointing both this transaction manager and your DAOs to it. This will lead to
 * optimized handling of "empty" transactions, that is, transactions without any
 * statements executed. LazyConnectionDataSourceProxy will not fetch a JDBC
 * Connection from the target DataSource until the first statement execution,
 * lazily applying the specified transaction settings to the target Conection.
 *
 * <p>On JDBC 3.0, this transaction manager supports nested transactions via JDBC
 * 3.0 Savepoints. The "nestedTransactionAllowed" flag defaults to true, as nested
 * transactions work without restrictions on JDBC drivers that support Savepoints
 * (such as the Oracle JDBC driver).
 *
 * <p>This implementation can be used as a replacement for JtaTransactionManager in the
 * single resource case, as it does not require a container that supports JTA: typically,
 * in combination with a locally defined JDBC DataSource (e.g. a Jakarta Commons DBCP
 * connection pool). Switching between this local strategy and a JTA environment is
 * just a matter of configuration, if you stick to the required connection lookup
 * pattern. Note that JTA does not support custom isolation levels!
 *
 * @author Juergen Hoeller
 * @since 02.05.2003
 * @see #setNestedTransactionAllowed
 * @see java.sql.Savepoint
 * @see DataSourceUtils#getConnection(javax.sql.DataSource)
 * @see DataSourceUtils#applyTransactionTimeout
 * @see DataSourceUtils#releaseConnection
 * @see TransactionAwareDataSourceProxy
 * @see LazyConnectionDataSourceProxy
 * @see org.springframework.jdbc.core.JdbcTemplate
 * @see org.springframework.jdbc.object
 */
public class DataSourceTransactionManager extends AbstractPlatformTransactionManager implements InitializingBean {

	private DataSource dataSource;


	/**
	 * Create a new DataSourceTransactionManager instance.
	 * A DataSource has to be set to be able to use it.
	 * @see #setDataSource
	 */
	public DataSourceTransactionManager() {
		setNestedTransactionAllowed(true);
	}

	/**
	 * Create a new DataSourceTransactionManager instance.
	 * @param dataSource JDBC DataSource to manage transactions for
	 */
	public DataSourceTransactionManager(DataSource dataSource) {
		this();
		setDataSource(dataSource);
		afterPropertiesSet();
	}

	/**
	 * Set the JDBC DataSource that this instance should manage transactions for.
	 * <p>This will typically be a locally defined DataSource, for example a
	 * Jakarta Commons DBCP connection pool. Alternatively, you can also drive
	 * transactions for a non-XA J2EE DataSource fetched from JNDI. For an XA
	 * DataSource, use JtaTransactionManager.
	 * <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 TransactionAwareDataSourceProxy
	 * @see org.springframework.transaction.jta.JtaTransactionManager
	 */
	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 dataSource;
	}

	public void afterPropertiesSet() {
		if (this.dataSource == null) {
			throw new IllegalArgumentException("dataSource is required");
		}
	}


	protected Object doGetTransaction() {
		DataSourceTransactionObject txObject = new DataSourceTransactionObject();
		txObject.setSavepointAllowed(isNestedTransactionAllowed());
		ConnectionHolder conHolder =
		    (ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
		txObject.setConnectionHolder(conHolder, false);
		return txObject;
	}

	protected boolean isExistingTransaction(Object transaction) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		return (txObject.getConnectionHolder() != null && txObject.getConnectionHolder().isTransactionActive());
	}

	/**
	 * This implementation sets the isolation level but ignores the timeout.
	 */
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;

		Connection con = null;

		try {
			if (txObject.getConnectionHolder() == null) {
				Connection newCon = this.dataSource.getConnection();
				if (logger.isDebugEnabled()) {
					logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
				}
				txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
			}

			txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
			con = txObject.getConnectionHolder().getConnection();

			Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
			txObject.setPreviousIsolationLevel(previousIsolationLevel);

			// Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
			// so we don't want to do it unnecessarily (for example if we've explicitly
			// configured the connection pool to set it already).
			if (con.getAutoCommit()) {
				txObject.setMustRestoreAutoCommit(true);
				if (logger.isDebugEnabled()) {
					logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
				}
				con.setAutoCommit(false);
			}
			txObject.getConnectionHolder().setTransactionActive(true);

			if (definition.getTimeout() != TransactionDefinition.TIMEOUT_DEFAULT) {
				txObject.getConnectionHolder().setTimeoutInSeconds(definition.getTimeout());
			}

			// Bind the session holder to the thread.
			if (txObject.isNewConnectionHolder()) {
				TransactionSynchronizationManager.bindResource(getDataSource(), txObject.getConnectionHolder());
			}
		}

		catch (SQLException ex) {
			DataSourceUtils.releaseConnection(con, this.dataSource);
			throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
		}
	}

	protected Object doSuspend(Object transaction) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		txObject.setConnectionHolder(null);
		ConnectionHolder conHolder = (ConnectionHolder)
				TransactionSynchronizationManager.unbindResource(this.dataSource);
		return conHolder;
	}

	protected void doResume(Object transaction, Object suspendedResources) {
		ConnectionHolder conHolder = (ConnectionHolder) suspendedResources;
		TransactionSynchronizationManager.bindResource(this.dataSource, conHolder);
	}

	protected void doCommit(DefaultTransactionStatus status) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		Connection con = txObject.getConnectionHolder().getConnection();
		if (status.isDebug()) {
			logger.debug("Committing JDBC transaction on Connection [" + con + "]");
		}
		try {
			con.commit();
		}
		catch (SQLException ex) {
			throw new TransactionSystemException("Could not commit JDBC transaction", ex);
		}
	}

	protected void doRollback(DefaultTransactionStatus status) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		Connection con = txObject.getConnectionHolder().getConnection();
		if (status.isDebug()) {
			logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
		}
		try {
			con.rollback();
		}
		catch (SQLException ex) {
			throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
		}
	}

	protected void doSetRollbackOnly(DefaultTransactionStatus status) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Setting JDBC transaction [" + txObject.getConnectionHolder().getConnection() +
					"] rollback-only");
		}
		txObject.setRollbackOnly();
	}

	protected void doCleanupAfterCompletion(Object transaction) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;

		// Remove the connection holder from the thread, if exposed.
		if (txObject.isNewConnectionHolder()) {
			TransactionSynchronizationManager.unbindResource(this.dataSource);
		}

		// Reset connection.
		Connection con = txObject.getConnectionHolder().getConnection();
		try {
			if (txObject.isMustRestoreAutoCommit()) {
				con.setAutoCommit(true);
			}
			DataSourceUtils.resetConnectionAfterTransaction(con, txObject.getPreviousIsolationLevel());
		}
		catch (Throwable ex) {
			logger.debug("Could not reset JDBC Connection after transaction", ex);
		}

		if (txObject.isNewConnectionHolder()) {
			if (logger.isDebugEnabled()) {
				logger.debug("Releasing JDBC Connection [" + con + "] after transaction");
			}
			DataSourceUtils.releaseConnection(con, this.dataSource);
		}

		txObject.getConnectionHolder().clear();
	}


	/**
	 * DataSource transaction object, representing a ConnectionHolder.
	 * Used as transaction object by DataSourceTransactionManager.
	 *
	 * <p>Derives from JdbcTransactionObjectSupport to inherit the capability
	 * to manage JDBC 3.0 Savepoints.
	 *
	 * @see ConnectionHolder
	 */
	private static class DataSourceTransactionObject extends JdbcTransactionObjectSupport {

		private boolean newConnectionHolder;

		private boolean mustRestoreAutoCommit;

		public void setConnectionHolder(ConnectionHolder connectionHolder, boolean newConnectionHolder) {
			super.setConnectionHolder(connectionHolder);
			this.newConnectionHolder = newConnectionHolder;
		}

		public boolean isNewConnectionHolder() {
			return newConnectionHolder;
		}

		public boolean hasTransaction() {
			return (getConnectionHolder() != null && getConnectionHolder().isTransactionActive());
		}

		public void setMustRestoreAutoCommit(boolean mustRestoreAutoCommit) {
			this.mustRestoreAutoCommit = mustRestoreAutoCommit;
		}

		public boolean isMustRestoreAutoCommit() {
			return mustRestoreAutoCommit;
		}

		public void setRollbackOnly() {
			getConnectionHolder().setRollbackOnly();
		}

		public boolean isRollbackOnly() {
			return getConnectionHolder().isRollbackOnly();
		}

	}
}