001/*
002 * Licensed to DuraSpace under one or more contributor license agreements.
003 * See the NOTICE file distributed with this work for additional information
004 * regarding copyright ownership.
005 *
006 * DuraSpace licenses this file to you under the Apache License,
007 * Version 2.0 (the "License"); you may not use this file except in
008 * compliance with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.fcrepo.http.api;
019
020import org.fcrepo.kernel.api.FedoraSession;
021import org.fcrepo.kernel.api.services.NodeService;
022
023/**
024 * An interface representing a utility whose locking methods can enforce
025 * the kinds of concurrency restrictions appropriate for an otherwise
026 * concurrency-naive application that operates on hierarchical resources
027 * represented by paths (as in URIs or filesystems).
028 *
029 * @author Mike Durbin
030 */
031public interface PathLockManager {
032
033    /**
034     * An interface representing a lock (comparable to that defined in
035     * java.util.concurrent.locks) that has been acquired.  Memory management
036     * for instances of this lock is handled by LockManager instances and
037     * anyone else receiving one of these such locks from a LockManager
038     * should not retain a reference to the used lock after releasing it.
039     */
040    public interface AcquiredLock {
041
042        /**
043         * Releases the lock, after which it's useless.
044         */
045        public void release();
046    }
047
048    /**
049     * Locks the necessary resources affected in order to safely view a resource
050     * at the given path.  A successful return from this method should guarantee
051     * that until release() is invoked on the returned Lock that no changes are made
052     * to the resource that would affect its display.
053     *
054     * @param path the path to a resource to be viewed
055     * @return an acquired Lock on the relevant resources
056     */
057    public AcquiredLock lockForRead(String path);
058
059    /**
060     * Locks the necessary resources affected in order to safely write to a resource
061     * at the given path.  A successful return from this method should guarantee
062     * that until release() is invoked on the returned Lock that no other callers
063     * may be granted locks necessary to add, modify or delete the resource at the
064     * provided path.
065     *
066     * @param path the path to a resource to be created (may involve implicitly created
067     *        resources at parent paths)
068     * @param session the current session
069     * @param nodeService the repository NodeService implementation
070     * @return an acquired Lock on the relevant resources
071     */
072    public AcquiredLock lockForWrite(String path, FedoraSession session, NodeService nodeService);
073
074    /**
075     * Locks the necessary resources affected in order to safely delete a resource
076     * at the given path.  A successful return from this method should guarantee
077     * that until release() is invoked on the returned Lock that no other callers
078     * may be granted locks necessary to add, modify or delete the resource at the
079     * provided path or any child path (because deletes cascade).
080     *
081     * @param path the path to a resource to be deleted (may imply the deletion of
082     *        all descendant resources)
083     * @return an acquired Lock on the relevant resources
084     */
085    public AcquiredLock lockForDelete(String path);
086
087}