| /* |
| * 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.commons.vfs2.cache; |
| |
| import java.lang.ref.Reference; |
| import java.lang.ref.ReferenceQueue; |
| import java.lang.ref.SoftReference; |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.atomic.AtomicReference; |
| import java.util.concurrent.locks.Lock; |
| import java.util.concurrent.locks.ReentrantLock; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.commons.vfs2.FileName; |
| import org.apache.commons.vfs2.FileObject; |
| import org.apache.commons.vfs2.FileSystem; |
| import org.apache.commons.vfs2.VfsLog; |
| import org.apache.commons.vfs2.util.Messages; |
| |
| /** |
| * This implementation caches every file as long as it is strongly reachable by |
| * the java vm. As soon as the vm needs memory - every softly reachable file |
| * will be discarded. |
| * |
| * @see SoftReference |
| */ |
| public class SoftRefFilesCache extends AbstractFilesCache |
| { |
| private static final int TIMEOUT = 1000; |
| |
| private static final Log log = LogFactory.getLog(SoftRefFilesCache.class); |
| |
| private final ConcurrentMap<FileSystem, Map<FileName, Reference<FileObject>>> fileSystemCache = |
| new ConcurrentHashMap<FileSystem, Map<FileName, Reference<FileObject>>>(); |
| private final Map<Reference<FileObject>, FileSystemAndNameKey> refReverseMap = |
| new HashMap<Reference<FileObject>, FileSystemAndNameKey>(100); |
| private final ReferenceQueue<FileObject> refQueue = new ReferenceQueue<FileObject>(); |
| |
| private volatile SoftRefReleaseThread softRefReleaseThread = null; // @GuardedBy("lock") |
| |
| private final Lock lock = new ReentrantLock(); |
| |
| |
| /** |
| * This thread will listen on the ReferenceQueue and remove the entry in the |
| * filescache as soon as the vm removes the reference |
| */ |
| private final class SoftRefReleaseThread extends Thread |
| { |
| private volatile boolean requestEnd; // used for inter-thread communication |
| |
| private SoftRefReleaseThread() |
| { |
| setName(SoftRefReleaseThread.class.getName()); |
| setDaemon(true); |
| } |
| |
| @Override |
| public void run() |
| { |
| loop: while (!requestEnd && !Thread.currentThread().isInterrupted()) |
| { |
| try |
| { |
| final Reference<?> ref = refQueue.remove(TIMEOUT); |
| if (ref == null) |
| { |
| continue; |
| } |
| |
| lock.lock(); |
| try |
| { |
| final FileSystemAndNameKey key = refReverseMap.get(ref); |
| |
| if (key != null && removeFile(key)) |
| { |
| close(key.getFileSystem()); |
| } |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| catch (final InterruptedException e) |
| { |
| if (!requestEnd) |
| { |
| VfsLog.warn(getLogger(), log, |
| Messages.getString("vfs.impl/SoftRefReleaseThread-interrupt.info")); |
| } |
| break loop; |
| } |
| } |
| } |
| } |
| |
| public SoftRefFilesCache() |
| { |
| } |
| |
| private void startThread() |
| { |
| // Double Checked Locking is allowed when volatile |
| if (softRefReleaseThread != null) |
| { |
| return; |
| } |
| |
| synchronized (lock) |
| { |
| if (softRefReleaseThread == null) |
| { |
| softRefReleaseThread = new SoftRefReleaseThread(); |
| softRefReleaseThread.start(); |
| } |
| } |
| } |
| |
| private void endThread() |
| { |
| synchronized (lock) |
| { |
| final SoftRefReleaseThread thread = softRefReleaseThread; |
| softRefReleaseThread = null; |
| if (thread != null) |
| { |
| thread.requestEnd = true; |
| thread.interrupt(); |
| } |
| } |
| } |
| |
| @Override |
| public void putFile(final FileObject fileObject) |
| { |
| if (log.isDebugEnabled()) |
| { |
| log.debug("putFile: " + this.getSafeName(fileObject)); |
| } |
| |
| final Map<FileName, Reference<FileObject>> files = getOrCreateFilesystemCache(fileObject.getFileSystem()); |
| |
| final Reference<FileObject> ref = createReference(fileObject, refQueue); |
| final FileSystemAndNameKey key = new FileSystemAndNameKey(fileObject.getFileSystem(), fileObject.getName()); |
| |
| lock.lock(); |
| try |
| { |
| final Reference<FileObject> old = files.put(fileObject.getName(), ref); |
| if (old != null) |
| { |
| refReverseMap.remove(old); |
| } |
| refReverseMap.put(ref, key); |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| private String getSafeName(final FileName fileName) |
| { |
| return fileName.getFriendlyURI(); |
| } |
| |
| private String getSafeName(final FileObject fileObject) |
| { |
| return this.getSafeName(fileObject.getName()); |
| } |
| |
| @Override |
| public boolean putFileIfAbsent(final FileObject fileObject) |
| { |
| if (log.isDebugEnabled()) |
| { |
| log.debug("putFile: " + this.getSafeName(fileObject)); |
| } |
| |
| final Map<FileName, Reference<FileObject>> files = getOrCreateFilesystemCache(fileObject.getFileSystem()); |
| |
| final Reference<FileObject> ref = createReference(fileObject, refQueue); |
| final FileSystemAndNameKey key = new FileSystemAndNameKey(fileObject.getFileSystem(), fileObject.getName()); |
| |
| lock.lock(); |
| try |
| { |
| if (files.containsKey(fileObject.getName()) && files.get(fileObject.getName()).get() != null) |
| { |
| return false; |
| } |
| final Reference<FileObject> old = files.put(fileObject.getName(), ref); |
| if (old != null) |
| { |
| refReverseMap.remove(old); |
| } |
| refReverseMap.put(ref, key); |
| return true; |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| protected Reference<FileObject> createReference(final FileObject file, final ReferenceQueue<FileObject> refqueue) |
| { |
| return new SoftReference<FileObject>(file, refqueue); |
| } |
| |
| @Override |
| public FileObject getFile(final FileSystem fileSystem, final FileName fileName) |
| { |
| final Map<FileName, Reference<FileObject>> files = getOrCreateFilesystemCache(fileSystem); |
| |
| lock.lock(); |
| try |
| { |
| final Reference<FileObject> ref = files.get(fileName); |
| if (ref == null) |
| { |
| return null; |
| } |
| |
| final FileObject fo = ref.get(); |
| if (fo == null) |
| { |
| removeFile(fileSystem, fileName); |
| } |
| return fo; |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public void clear(final FileSystem fileSystem) |
| { |
| final Map<FileName, Reference<FileObject>> files = getOrCreateFilesystemCache(fileSystem); |
| |
| lock.lock(); |
| try |
| { |
| final Iterator<FileSystemAndNameKey> iterKeys = refReverseMap.values().iterator(); |
| while (iterKeys.hasNext()) |
| { |
| final FileSystemAndNameKey key = iterKeys.next(); |
| if (key.getFileSystem() == fileSystem) |
| { |
| iterKeys.remove(); |
| files.remove(key.getFileName()); |
| } |
| } |
| |
| if (files.size() < 1) |
| { |
| close(fileSystem); |
| } |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Called while the lock is held |
| * @param fileSystem The file system to close. |
| */ |
| private void close(final FileSystem fileSystem) |
| { |
| if (log.isDebugEnabled()) |
| { |
| log.debug("close fs: " + fileSystem.getRootName()); |
| } |
| |
| fileSystemCache.remove(fileSystem); |
| if (fileSystemCache.size() < 1) |
| { |
| endThread(); |
| } |
| /* This is not thread-safe as another thread might be opening the file system |
| ((DefaultFileSystemManager) getContext().getFileSystemManager()) |
| ._closeFileSystem(filesystem); |
| */ |
| } |
| |
| @Override |
| public void close() |
| { |
| super.close(); |
| |
| endThread(); |
| |
| lock.lock(); |
| try |
| { |
| fileSystemCache.clear(); |
| |
| refReverseMap.clear(); |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public void removeFile(final FileSystem fileSystem, final FileName fileName) |
| { |
| if (removeFile(new FileSystemAndNameKey(fileSystem, fileName))) |
| { |
| close(fileSystem); |
| } |
| } |
| |
| private boolean removeFile(final FileSystemAndNameKey key) |
| { |
| if (log.isDebugEnabled()) |
| { |
| log.debug("removeFile: " + this.getSafeName(key.getFileName())); |
| } |
| |
| final Map<?, ?> files = getOrCreateFilesystemCache(key.getFileSystem()); |
| |
| lock.lock(); |
| try |
| { |
| final Object ref = files.remove(key.getFileName()); |
| if (ref != null) |
| { |
| refReverseMap.remove(ref); |
| } |
| |
| return files.size() < 1; |
| } |
| finally |
| { |
| lock.unlock(); |
| } |
| } |
| |
| protected Map<FileName, Reference<FileObject>> getOrCreateFilesystemCache(final FileSystem fileSystem) |
| { |
| if (fileSystemCache.size() < 1) |
| { |
| startThread(); |
| } |
| |
| Map<FileName, Reference<FileObject>> files; |
| |
| do |
| { |
| files = fileSystemCache.get(fileSystem); |
| if (files != null) |
| { |
| break; |
| } |
| files = new HashMap<FileName, Reference<FileObject>>(); |
| } while (fileSystemCache.putIfAbsent(fileSystem, files) == null); |
| |
| return files; |
| } |
| } |