/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      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.SQLException;
import java.sql.Savepoint;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.lang.Nullable;
import org.springframework.transaction.CannotCreateTransactionException;
import org.springframework.transaction.NestedTransactionNotSupportedException;
import org.springframework.transaction.SavepointManager;
import org.springframework.transaction.TransactionException;
import org.springframework.transaction.TransactionSystemException;
import org.springframework.transaction.TransactionUsageException;
import org.springframework.transaction.support.SmartTransactionObject;
import org.springframework.util.Assert;

Convenient base class for JDBC-aware transaction objects. Can contain a ConnectionHolder with a JDBC Connection, and implements the SavepointManager interface based on that ConnectionHolder. 
Allows for programmatic management of JDBC Savepoints. Spring's DefaultTransactionStatus automatically delegates to this, as it autodetects transaction objects which implement the SavepointManager interface. 
Author:
Juergen Hoeller
See Also:
DataSourceTransactionManager
Since:
1.1/**
 * Convenient base class for JDBC-aware transaction objects. Can contain a
 * {@link ConnectionHolder} with a JDBC {@code Connection}, and implements the
 * {@link SavepointManager} interface based on that {@code ConnectionHolder}.
 *
 * <p>Allows for programmatic management of JDBC {@link java.sql.Savepoint Savepoints}.
 * Spring's {@link org.springframework.transaction.support.DefaultTransactionStatus}
 * automatically delegates to this, as it autodetects transaction objects which
 * implement the {@link SavepointManager} interface.
 *
 * @author Juergen Hoeller
 * @since 1.1
 * @see DataSourceTransactionManager
 */
public abstract class JdbcTransactionObjectSupport implements SavepointManager, SmartTransactionObject {

	private static final Log logger = LogFactory.getLog(JdbcTransactionObjectSupport.class);


	@Nullable
	private ConnectionHolder connectionHolder;

	@Nullable
	private Integer previousIsolationLevel;

	private boolean savepointAllowed = false;


	public void setConnectionHolder(@Nullable ConnectionHolder connectionHolder) {
		this.connectionHolder = connectionHolder;
	}

	public ConnectionHolder getConnectionHolder() {
		Assert.state(this.connectionHolder != null, "No ConnectionHolder available");
		return this.connectionHolder;
	}

	public boolean hasConnectionHolder() {
		return (this.connectionHolder != null);
	}

	public void setPreviousIsolationLevel(@Nullable Integer previousIsolationLevel) {
		this.previousIsolationLevel = previousIsolationLevel;
	}

	@Nullable
	public Integer getPreviousIsolationLevel() {
		return this.previousIsolationLevel;
	}

	public void setSavepointAllowed(boolean savepointAllowed) {
		this.savepointAllowed = savepointAllowed;
	}

	public boolean isSavepointAllowed() {
		return this.savepointAllowed;
	}

	@Override
	public void flush() {
		// no-op
	}


	//---------------------------------------------------------------------
	// Implementation of SavepointManager
	//---------------------------------------------------------------------

	
This implementation creates a JDBC 3.0 Savepoint and returns it.
See Also:
setSavepoint.setSavepoint/**
	 * This implementation creates a JDBC 3.0 Savepoint and returns it.
	 * @see java.sql.Connection#setSavepoint
	 */
	@Override
	public Object createSavepoint() throws TransactionException {
		ConnectionHolder conHolder = getConnectionHolderForSavepoint();
		try {
			if (!conHolder.supportsSavepoints()) {
				throw new NestedTransactionNotSupportedException(
						"Cannot create a nested transaction because savepoints are not supported by your JDBC driver");
			}
			if (conHolder.isRollbackOnly()) {
				throw new CannotCreateTransactionException(
						"Cannot create savepoint for transaction which is already marked as rollback-only");
			}
			return conHolder.createSavepoint();
		}
		catch (SQLException ex) {
			throw new CannotCreateTransactionException("Could not create JDBC savepoint", ex);
		}
	}

	
This implementation rolls back to the given JDBC 3.0 Savepoint.
See Also:
rollback.rollback(Savepoint)/**
	 * This implementation rolls back to the given JDBC 3.0 Savepoint.
	 * @see java.sql.Connection#rollback(java.sql.Savepoint)
	 */
	@Override
	public void rollbackToSavepoint(Object savepoint) throws TransactionException {
		ConnectionHolder conHolder = getConnectionHolderForSavepoint();
		try {
			conHolder.getConnection().rollback((Savepoint) savepoint);
			conHolder.resetRollbackOnly();
		}
		catch (Throwable ex) {
			throw new TransactionSystemException("Could not roll back to JDBC savepoint", ex);
		}
	}

	
This implementation releases the given JDBC 3.0 Savepoint.
See Also:
releaseSavepoint.releaseSavepoint/**
	 * This implementation releases the given JDBC 3.0 Savepoint.
	 * @see java.sql.Connection#releaseSavepoint
	 */
	@Override
	public void releaseSavepoint(Object savepoint) throws TransactionException {
		ConnectionHolder conHolder = getConnectionHolderForSavepoint();
		try {
			conHolder.getConnection().releaseSavepoint((Savepoint) savepoint);
		}
		catch (Throwable ex) {
			logger.debug("Could not explicitly release JDBC savepoint", ex);
		}
	}

	protected ConnectionHolder getConnectionHolderForSavepoint() throws TransactionException {
		if (!isSavepointAllowed()) {
			throw new NestedTransactionNotSupportedException(
					"Transaction manager does not allow nested transactions");
		}
		if (!hasConnectionHolder()) {
			throw new TransactionUsageException(
					"Cannot create nested transaction when not exposing a JDBC transaction");
		}
		return getConnectionHolder();
	}

}