| /* |
| * 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.directory.mavibot.btree; |
| |
| |
| import java.util.Date; |
| |
| |
| /** |
| * The Transaction is used to protect the BTree against concurrent modification, |
| * and insure that a read is always done against one single revision. It's also |
| * used to gather many modifications under one single revision, if needed. |
| * <p/> |
| * A Transaction should be closed when the user is done with it, otherwise the |
| * pages associated with the given revision, and all the referenced pages, will |
| * remain on the storage. |
| * <p/> |
| * A Transaction can be hold for quite a long time, for instance while doing |
| * a browse against a big BTree. At some point, transactions which are pending |
| * for too long will be closed by the transaction manager. |
| * |
| * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> |
| * |
| * @param <K> The type for the Key |
| * @param <V> The type for the stored value |
| */ |
| public class ReadTransaction<K, V> |
| { |
| /** The associated revision */ |
| private long revision; |
| |
| /** The date of creation */ |
| private long creationDate; |
| |
| /** The revision on which we are having a transaction */ |
| private volatile Page<K, V> root; |
| |
| /** A flag used to tell if a transaction is closed or not */ |
| private volatile boolean closed; |
| |
| |
| /** |
| * Creates a new transaction instance |
| * |
| * @param root The associated root |
| * @param revision The revision this transaction is using |
| * @param creationDate The creation date for this transaction |
| */ |
| public ReadTransaction( Page<K, V> root, long revision, long creationDate ) |
| { |
| this.revision = revision; |
| this.creationDate = creationDate; |
| this.root = root; |
| closed = false; |
| } |
| |
| |
| /** |
| * @return the associated revision |
| */ |
| public long getRevision() |
| { |
| return revision; |
| } |
| |
| |
| /** |
| * @return the associated root |
| */ |
| public Page<K, V> getRoot() |
| { |
| return root; |
| } |
| |
| |
| /** |
| * @return the creationDate |
| */ |
| public long getCreationDate() |
| { |
| return creationDate; |
| } |
| |
| |
| /** |
| * Close the transaction, releasing the revision it was using. |
| */ |
| public void close() |
| { |
| root = null; |
| closed = true; |
| } |
| |
| |
| /** |
| * @return true if this transaction has been closed |
| */ |
| public boolean isClosed() |
| { |
| return closed; |
| } |
| |
| |
| /** |
| * @see Object#toString() |
| */ |
| public String toString() |
| { |
| return "Transaction[" + revision + ":" + new Date( creationDate ) + ", closed :" + closed + "]"; |
| } |
| } |