LockStrategy.java

/*
 *  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.ivy.plugins.lock;

import java.io.File;

import org.apache.ivy.core.module.descriptor.Artifact;

/**
 * A lock strategy determines when and how lock should be performed when downloading data to a
 * cache.
 * <p>
 * Note that some implementations may actually choose to NOT perform locking, when no lock is
 * necessary (cache not shared). Some other implementations may choose to lock the cache for the
 * download of a whole module (not possible yet), or at the artifact level.
 * <p>
 * </p>
 * The lock methods should return true when the lock is either actually acquired or not performed by
 * the strategy. </p>
 * <p>
 * Locking used in the locking strategy must support reentrant lock. Reentrant locking should be
 * performed for the whole strategy.
 * </p>
 */
public interface LockStrategy {

    /**
     * Returns the name of the strategy
     * 
     * @return the name of the strategy
     */
    String getName();

    /**
     * Performs a lock before downloading the given {@link Artifact} to the given file.
     * 
     * @param artifact
     *            the artifact about to be downloaded
     * @param artifactFileToDownload
     *            the file where the artifact will be downloaded
     * @return true if the artifact is locked, false otherwise
     * @throws InterruptedException
     *             if the thread is interrupted while waiting to acquire the lock
     */
    boolean lockArtifact(Artifact artifact, File artifactFileToDownload)
            throws InterruptedException;

    /**
     * Release the lock acquired for an artifact download.
     * 
     * @param artifact
     *            the artifact for which the lock was acquired
     * @param artifactFileToDownload
     *            the file where the artifact is supposed to have been downloaded
     */
    void unlockArtifact(Artifact artifact, File artifactFileToDownload);

}