001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.transaction.locking;
018
019/**
020 * A manager for multi level locks on resources. Encapsulates creation, removal, and retrieval of locks.
021 * Each resource can have at most a single lock. However, it may be possible for more than one
022 * accessing entity to have influence on this lock via different lock levels that may be 
023 * provided by the according implementation of {@link MultiLevelLock}. 
024 * 
025 * @version $Id: LockManager.java 493628 2007-01-07 01:42:48Z joerg $
026 * @see MultiLevelLock
027 */
028public interface LockManager {
029
030    /**
031     * Either gets an existing lock on the specified resource or creates one if none exists. 
032     * This methods guarantees to do this atomically. 
033     * 
034     * @param resourceId the resource to get or create the lock on
035     * @return the lock for the specified resource
036     */
037    public MultiLevelLock atomicGetOrCreateLock(Object resourceId);
038
039    /**
040     * Gets an existing lock on the specified resource. If none exists it returns <code>null</code>. 
041     * 
042     * @param resourceId the resource to get the lock for
043     * @return the lock on the specified resource
044     */
045    public MultiLevelLock getLock(Object resourceId);
046
047    /**
048     * Removes the specified lock from the associated resource. 
049     * 
050     * @param lock the lock to be removed
051     */
052    public void removeLock(MultiLevelLock lock);
053}