Java tutorial
/* * #%L * Alfresco Repository * %% * Copyright (C) 2005 - 2016 Alfresco Software Limited * %% * This file is part of the Alfresco software. * If the software was purchased under a paid Alfresco license, the terms of * the paid license agreement will prevail. Otherwise, the software is * provided under the following open source license terms: * * Alfresco is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * Alfresco is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with Alfresco. If not, see <http://www.gnu.org/licenses/>. * #L% */ package org.alfresco.filesys.alfresco; import java.io.IOException; import java.util.concurrent.Callable; import javax.transaction.Status; import javax.transaction.UserTransaction; import org.alfresco.error.AlfrescoRuntimeException; import org.alfresco.jlan.server.SrvSession; import org.alfresco.jlan.server.core.DeviceContext; import org.alfresco.jlan.server.core.DeviceContextException; import org.alfresco.jlan.server.filesys.IOControlNotImplementedException; import org.alfresco.jlan.server.filesys.IOCtlInterface; import org.alfresco.jlan.server.filesys.NetworkFile; import org.alfresco.jlan.server.filesys.TransactionalFilesystemInterface; import org.alfresco.jlan.server.filesys.TreeConnection; import org.alfresco.jlan.smb.SMBException; import org.alfresco.jlan.smb.SMBStatus; import org.alfresco.jlan.util.DataBuffer; import org.alfresco.repo.transaction.RetryingTransactionHelper; import org.alfresco.service.ServiceRegistry; import org.alfresco.service.transaction.TransactionService; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * Alfresco Tx Disk Driver Base Class * * <p>Provides common code to the Alfresco filesystem implementations. * * @author gkspencer */ public abstract class AlfrescoTxDiskDriver extends AlfrescoDiskDriver implements TransactionalFilesystemInterface { private static final Log logger = LogFactory.getLog(AlfrescoTxDiskDriver.class); // Remember whether the current thread is already in a retrying transaction private ThreadLocal<Boolean> m_inRetryingTransaction = new ThreadLocal<Boolean>(); /** * Begin a read-only transaction * * @param sess SrvSession */ public void beginReadTransaction(SrvSession sess) { beginTransaction(sess, true); } /** * Begin a writeable transaction * * @param sess SrvSession */ public void beginWriteTransaction(SrvSession sess) { beginTransaction(sess, false); } /** * Perform a retryable operation in a write transaction * <p> * WARNING : side effect - that the current transaction, if any, is ended. * * * @param sess * the server session * @param callback * callback for the retryable operation * @return the result of the operation * @throws IOException */ public <T> T doInWriteTransaction(SrvSession sess, final CallableIO<T> callback) throws IOException { Boolean wasInRetryingTransaction = m_inRetryingTransaction.get(); try { boolean hadTransaction = sess.hasTransaction(); if (hadTransaction) { sess.endTransaction(); } m_inRetryingTransaction.set(Boolean.TRUE); T result = m_transactionService.getRetryingTransactionHelper() .doInTransaction(new RetryingTransactionHelper.RetryingTransactionCallback<T>() { public T execute() throws Throwable { try { return callback.call(); } catch (IOException e) { // Ensure original checked IOExceptions get propagated throw new PropagatingException(e); } } }); if (hadTransaction) { beginReadTransaction(sess); } return result; } catch (PropagatingException e) { // Unwrap checked exceptions throw (IOException) e.getCause(); } finally { m_inRetryingTransaction.set(wasInRetryingTransaction); } } /** * End an active transaction * * @param sess SrvSession * @param tx Object */ public void endTransaction(SrvSession sess, Object tx) { // Check that the transaction object is valid if (tx == null) return; // Get the filesystem transaction FilesysTransaction filesysTx = (FilesysTransaction) tx; // Check if there is an active transaction if (filesysTx != null && filesysTx.hasTransaction()) { // Get the active transaction UserTransaction ftx = filesysTx.getTransaction(); try { // Commit or rollback the transaction if (ftx.getStatus() == Status.STATUS_MARKED_ROLLBACK || ftx.getStatus() == Status.STATUS_ROLLEDBACK || ftx.getStatus() == Status.STATUS_ROLLING_BACK) { // Transaction is marked for rollback ftx.rollback(); // DEBUG if (logger.isDebugEnabled()) logger.debug("End transaction (rollback)"); } else { // Commit the transaction ftx.commit(); // DEBUG if (logger.isDebugEnabled()) logger.debug("End transaction (commit)"); } } catch (Exception ex) { if (logger.isDebugEnabled()) logger.debug("Failed to end transaction, " + ex.getMessage()); // throw new AlfrescoRuntimeException("Failed to end transaction", ex); } finally { // Clear the current transaction sess.clearTransaction(); } } } /** * Create and start a transaction, if not already active * * @param sess SrvSession * @param readOnly boolean * @exception AlfrescoRuntimeException */ private final void beginTransaction(SrvSession sess, boolean readOnly) throws AlfrescoRuntimeException { // Do nothing if we are already in a retrying transaction Boolean inRetryingTransaction = m_inRetryingTransaction.get(); if (inRetryingTransaction != null && inRetryingTransaction) { return; } // Initialize the per session thread local that holds the transaction sess.initializeTransactionObject(); // Get the filesystem transaction FilesysTransaction filesysTx = (FilesysTransaction) sess.getTransactionObject().get(); if (filesysTx == null) { filesysTx = new FilesysTransaction(); sess.getTransactionObject().set(filesysTx); } // If there is an active transaction check that it is the required type if (filesysTx.hasTransaction()) { // Get the active transaction UserTransaction tx = filesysTx.getTransaction(); // Check if the current transaction is marked for rollback try { if (tx.getStatus() == Status.STATUS_MARKED_ROLLBACK || tx.getStatus() == Status.STATUS_ROLLEDBACK || tx.getStatus() == Status.STATUS_ROLLING_BACK) { // Rollback the current transaction tx.rollback(); } } catch (Exception ex) { } // Check if the transaction is a write transaction, if write has been requested if (readOnly == false && filesysTx.isReadOnly() == true) { // Commit the read-only transaction try { tx.commit(); } catch (Exception ex) { throw new AlfrescoRuntimeException( "Failed to commit read-only transaction, " + ex.getMessage()); } finally { // Clear the active transaction filesysTx.clearTransaction(); } } } // Create the transaction if (filesysTx.hasTransaction() == false) { try { // Create a new transaction UserTransaction userTrans = m_transactionService.getUserTransaction(readOnly); userTrans.begin(); // Store the transaction filesysTx.setTransaction(userTrans, readOnly); // DEBUG if (logger.isDebugEnabled()) logger.debug("Created transaction readOnly=" + readOnly); } catch (Exception ex) { throw new AlfrescoRuntimeException("Failed to create transaction, " + ex.getMessage()); } } // Store the transaction callback sess.setTransaction(this); } /** * An extended {@link Callable} that throws {@link IOException}s. * * @param <V> */ public interface CallableIO<V> extends Callable<V> { public V call() throws IOException; } /** * A wrapper for checked exceptions to be passed through the retrying transaction handler. */ protected static class PropagatingException extends RuntimeException { private static final long serialVersionUID = 1L; /** * @param cause Throwable */ public PropagatingException(Throwable cause) { super(cause); } } }