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Apache Commons DBCP software implements Database Connection Pooling
/**
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.dbcp2.managed;
import org.apache.commons.dbcp2.ConnectionFactory;
import javax.transaction.TransactionManager;
import javax.transaction.xa.XAException;
import javax.transaction.xa.XAResource;
import javax.transaction.xa.Xid;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Objects;
/**
* An implementation of XAConnectionFactory which manages non-XA connections in XA transactions. A non-XA connection
* commits and rolls back as part of the XA transaction, but is not recoverable since the connection does not implement
* the 2-phase protocol.
*
* @since 2.0
*/
public class LocalXAConnectionFactory implements XAConnectionFactory {
private final TransactionRegistry transactionRegistry;
private final ConnectionFactory connectionFactory;
/**
* Creates an LocalXAConnectionFactory which uses the specified connection factory to create database connections.
* The connections are enlisted into transactions using the specified transaction manager.
*
* @param transactionManager
* the transaction manager in which connections will be enlisted
* @param connectionFactory
* the connection factory from which connections will be retrieved
*/
public LocalXAConnectionFactory(final TransactionManager transactionManager,
final ConnectionFactory connectionFactory) {
Objects.requireNonNull(transactionManager, "transactionManager is null");
Objects.requireNonNull(connectionFactory, "connectionFactory is null");
this.transactionRegistry = new TransactionRegistry(transactionManager);
this.connectionFactory = connectionFactory;
}
@Override
public TransactionRegistry getTransactionRegistry() {
return transactionRegistry;
}
@Override
public Connection createConnection() throws SQLException {
// create a new connection
final Connection connection = connectionFactory.createConnection();
// create a XAResource to manage the connection during XA transactions
final XAResource xaResource = new LocalXAResource(connection);
// register the xa resource for the connection
transactionRegistry.registerConnection(connection, xaResource);
return connection;
}
/**
* LocalXAResource is a fake XAResource for non-XA connections. When a transaction is started the connection
* auto-commit is turned off. When the connection is committed or rolled back, the commit or rollback method is
* called on the connection and then the original auto-commit value is restored.
*
* The LocalXAResource also respects the connection read-only setting. If the connection is read-only the commit
* method will not be called, and the prepare method returns the XA_RDONLY.
*
* It is assumed that the wrapper around a managed connection disables the setAutoCommit(), commit(), rollback() and
* setReadOnly() methods while a transaction is in progress.
*
* @since 2.0
*/
protected static class LocalXAResource implements XAResource {
private final Connection connection;
private Xid currentXid; // @GuardedBy("this")
private boolean originalAutoCommit; // @GuardedBy("this")
public LocalXAResource(final Connection localTransaction) {
this.connection = localTransaction;
}
/**
* Gets the current xid of the transaction branch associated with this XAResource.
*
* @return the current xid of the transaction branch associated with this XAResource.
*/
public synchronized Xid getXid() {
return currentXid;
}
/**
* Signals that a the connection has been enrolled in a transaction. This method saves off the current auto
* commit flag, and then disables auto commit. The original auto commit setting is restored when the transaction
* completes.
*
* @param xid
* the id of the transaction branch for this connection
* @param flag
* either XAResource.TMNOFLAGS or XAResource.TMRESUME
* @throws XAException
* if the connection is already enlisted in another transaction, or if auto-commit could not be
* disabled
*/
@Override
public synchronized void start(final Xid xid, final int flag) throws XAException {
if (flag == XAResource.TMNOFLAGS) {
// first time in this transaction
// make sure we aren't already in another tx
if (this.currentXid != null) {
throw new XAException("Already enlisted in another transaction with xid " + xid);
}
// save off the current auto commit flag so it can be restored after the transaction completes
try {
originalAutoCommit = connection.getAutoCommit();
} catch (final SQLException ignored) {
// no big deal, just assume it was off
originalAutoCommit = true;
}
// update the auto commit flag
try {
connection.setAutoCommit(false);
} catch (final SQLException e) {
throw (XAException) new XAException("Count not turn off auto commit for a XA transaction")
.initCause(e);
}
this.currentXid = xid;
} else if (flag == XAResource.TMRESUME) {
if (!xid.equals(this.currentXid)) {
throw new XAException("Attempting to resume in different transaction: expected " + this.currentXid
+ ", but was " + xid);
}
} else {
throw new XAException("Unknown start flag " + flag);
}
}
/**
* This method does nothing.
*
* @param xid
* the id of the transaction branch for this connection
* @param flag
* ignored
* @throws XAException
* if the connection is already enlisted in another transaction
*/
@Override
public synchronized void end(final Xid xid, final int flag) throws XAException {
Objects.requireNonNull(xid, "xid is null");
if (!this.currentXid.equals(xid)) {
throw new XAException("Invalid Xid: expected " + this.currentXid + ", but was " + xid);
}
// This notification tells us that the application server is done using this
// connection for the time being. The connection is still associated with an
// open transaction, so we must still wait for the commit or rollback method
}
/**
* This method does nothing since the LocalXAConnection does not support two-phase-commit. This method will
* return XAResource.XA_RDONLY if the connection isReadOnly(). This assumes that the physical connection is
* wrapped with a proxy that prevents an application from changing the read-only flag while enrolled in a
* transaction.
*
* @param xid
* the id of the transaction branch for this connection
* @return XAResource.XA_RDONLY if the connection.isReadOnly(); XAResource.XA_OK otherwise
*/
@Override
public synchronized int prepare(final Xid xid) {
// if the connection is read-only, then the resource is read-only
// NOTE: this assumes that the outer proxy throws an exception when application code
// attempts to set this in a transaction
try {
if (connection.isReadOnly()) {
// update the auto commit flag
connection.setAutoCommit(originalAutoCommit);
// tell the transaction manager we are read only
return XAResource.XA_RDONLY;
}
} catch (final SQLException ignored) {
// no big deal
}
// this is a local (one phase) only connection, so we can't prepare
return XAResource.XA_OK;
}
/**
* Commits the transaction and restores the original auto commit setting.
*
* @param xid
* the id of the transaction branch for this connection
* @param flag
* ignored
* @throws XAException
* if connection.commit() throws a SQLException
*/
@Override
public synchronized void commit(final Xid xid, final boolean flag) throws XAException {
Objects.requireNonNull(xid, "xid is null");
if (this.currentXid == null) {
throw new XAException("There is no current transaction");
}
if (!this.currentXid.equals(xid)) {
throw new XAException("Invalid Xid: expected " + this.currentXid + ", but was " + xid);
}
try {
// make sure the connection isn't already closed
if (connection.isClosed()) {
throw new XAException("Connection is closed");
}
// A read only connection should not be committed
if (!connection.isReadOnly()) {
connection.commit();
}
} catch (final SQLException e) {
throw (XAException) new XAException().initCause(e);
} finally {
try {
connection.setAutoCommit(originalAutoCommit);
} catch (final SQLException e) {
// ignore
}
this.currentXid = null;
}
}
/**
* Rolls back the transaction and restores the original auto commit setting.
*
* @param xid
* the id of the transaction branch for this connection
* @throws XAException
* if connection.rollback() throws a SQLException
*/
@Override
public synchronized void rollback(final Xid xid) throws XAException {
Objects.requireNonNull(xid, "xid is null");
if (!this.currentXid.equals(xid)) {
throw new XAException("Invalid Xid: expected " + this.currentXid + ", but was " + xid);
}
try {
connection.rollback();
} catch (final SQLException e) {
throw (XAException) new XAException().initCause(e);
} finally {
try {
connection.setAutoCommit(originalAutoCommit);
} catch (final SQLException e) {
// Ignore.
}
this.currentXid = null;
}
}
/**
* Returns true if the specified XAResource == this XAResource.
*
* @param xaResource
* the XAResource to test
* @return true if the specified XAResource == this XAResource; false otherwise
*/
@Override
public boolean isSameRM(final XAResource xaResource) {
return this == xaResource;
}
/**
* Clears the currently associated transaction if it is the specified xid.
*
* @param xid
* the id of the transaction to forget
*/
@Override
public synchronized void forget(final Xid xid) {
if (xid != null && xid.equals(currentXid)) {
currentXid = null;
}
}
/**
* Always returns a zero length Xid array. The LocalXAConnectionFactory can not support recovery, so no xids
* will ever be found.
*
* @param flag
* ignored since recovery is not supported
* @return always a zero length Xid array.
*/
@Override
public Xid[] recover(final int flag) {
return new Xid[0];
}
/**
* Always returns 0 since we have no way to set a transaction timeout on a JDBC connection.
*
* @return always 0
*/
@Override
public int getTransactionTimeout() {
return 0;
}
/**
* Always returns false since we have no way to set a transaction timeout on a JDBC connection.
*
* @param transactionTimeout
* ignored since we have no way to set a transaction timeout on a JDBC connection
* @return always false
*/
@Override
public boolean setTransactionTimeout(final int transactionTimeout) {
return false;
}
}
}