Java tutorial
package org.apache.archiva.common.filelock; /* * 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. */ import org.apache.commons.lang.time.StopWatch; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Service; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.channels.ClosedChannelException; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; /** * @author Olivier Lamy * @since 2.0.0 */ @Service("fileLockManager#default") public class DefaultFileLockManager implements FileLockManager { // TODO currently we create lock for read and write!! // the idea could be to store lock here with various clients read/write // only read could be a more simple lock and acquire a write lock means waiting the end of all reading threads private static final ConcurrentMap<File, Lock> lockFiles = new ConcurrentHashMap<File, Lock>(64); private boolean skipLocking = true; private Logger log = LoggerFactory.getLogger(getClass()); private int timeout = 0; @Override public Lock readFileLock(File file) throws FileLockException, FileLockTimeoutException { if (skipLocking) { return new Lock(file); } StopWatch stopWatch = new StopWatch(); boolean acquired = false; mkdirs(file.getParentFile()); Lock lock = null; stopWatch.start(); while (!acquired) { if (timeout > 0) { long delta = stopWatch.getTime(); log.debug("delta {}, timeout {}", delta, timeout); if (delta > timeout) { log.warn("Cannot acquire read lock within {} millis. Will skip the file: {}", timeout, file); // we could not get the lock within the timeout period, so throw FileLockTimeoutException throw new FileLockTimeoutException(); } } Lock current = lockFiles.get(file); if (current != null) { log.debug("read lock file exist continue wait"); continue; } try { lock = new Lock(file, false); createNewFileQuietly(file); lock.openLock(false, timeout > 0); acquired = true; } catch (FileNotFoundException e) { // can happen if an other thread has deleted the file // close RandomAccessFile!!! if (lock != null) { closeQuietly(lock.getRandomAccessFile()); } log.debug("read Lock skip: {} try to create file", e.getMessage()); createNewFileQuietly(file); } catch (IOException e) { throw new FileLockException(e.getMessage(), e); } catch (IllegalStateException e) { log.debug("openLock {}:{}", e.getClass(), e.getMessage()); } } Lock current = lockFiles.putIfAbsent(file, lock); if (current != null) { lock = current; } return lock; } @Override public Lock writeFileLock(File file) throws FileLockException, FileLockTimeoutException { if (skipLocking) { return new Lock(file); } mkdirs(file.getParentFile()); StopWatch stopWatch = new StopWatch(); boolean acquired = false; Lock lock = null; stopWatch.start(); while (!acquired) { if (timeout > 0) { long delta = stopWatch.getTime(); log.debug("delta {}, timeout {}", delta, timeout); if (delta > timeout) { log.warn("Cannot acquire read lock within {} millis. Will skip the file: {}", timeout, file); // we could not get the lock within the timeout period, so throw FileLockTimeoutException throw new FileLockTimeoutException(); } } Lock current = lockFiles.get(file); try { if (current != null) { log.debug("write lock file exist continue wait"); continue; } lock = new Lock(file, true); createNewFileQuietly(file); lock.openLock(true, timeout > 0); acquired = true; } catch (FileNotFoundException e) { // can happen if an other thread has deleted the file // close RandomAccessFile!!! if (lock != null) { closeQuietly(lock.getRandomAccessFile()); } log.debug("write Lock skip: {} try to create file", e.getMessage()); createNewFileQuietly(file); } catch (IOException e) { throw new FileLockException(e.getMessage(), e); } catch (IllegalStateException e) { log.debug("openLock {}:{}", e.getClass(), e.getMessage()); } } Lock current = lockFiles.putIfAbsent(file, lock); if (current != null) { lock = current; } return lock; } private void closeQuietly(RandomAccessFile randomAccessFile) { if (randomAccessFile == null) { return; } try { randomAccessFile.close(); } catch (IOException e) { // ignore } } private void createNewFileQuietly(File file) { try { file.createNewFile(); } catch (IOException e) { // skip that } } @Override public void release(Lock lock) throws FileLockException { if (lock == null) { log.debug("skip releasing null"); return; } if (skipLocking) { return; } try { lockFiles.remove(lock.getFile()); lock.close(); } catch (ClosedChannelException e) { // skip this one log.debug("ignore ClosedChannelException: {}", e.getMessage()); } catch (IOException e) { throw new FileLockException(e.getMessage(), e); } } @Override public void clearLockFiles() { lockFiles.clear(); } private boolean mkdirs(File directory) { return directory.mkdirs(); } @Override public int getTimeout() { return timeout; } @Override public void setTimeout(int timeout) { this.timeout = timeout; } @Override public boolean isSkipLocking() { return skipLocking; } @Override public void setSkipLocking(boolean skipLocking) { this.skipLocking = skipLocking; } }