org.apache.commons.vfs2.cache.LRUFilesCache Maven / Gradle / Ivy
/*
* 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.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.commons.collections4.map.AbstractLinkedMap;
import org.apache.commons.collections4.map.LRUMap;
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.FileSystemException;
import org.apache.commons.vfs2.VfsLog;
import org.apache.commons.vfs2.util.Messages;
/**
* This implementation caches every file using {@link LRUMap}.
*
* The default constructor uses a LRU size of 100 per file system.
*
*/
public class LRUFilesCache extends AbstractFilesCache {
/** The default LRU size */
private static final int DEFAULT_LRU_SIZE = 100;
/** The logger to use. */
private static final Log log = LogFactory.getLog(LRUFilesCache.class);
/** The FileSystem cache */
private final ConcurrentMap> filesystemCache = new ConcurrentHashMap<>(10);
/** The size of the cache */
private final int lruSize;
private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
private final Lock readLock = rwLock.readLock();
private final Lock writeLock = rwLock.writeLock();
/**
* The file cache
*/
private class MyLRUMap extends LRUMap {
/**
* serialVersionUID format is YYYYMMDD for the date of the last binary change.
*/
private static final long serialVersionUID = 20101208L;
/** The FileSystem */
private final FileSystem filesystem;
public MyLRUMap(final FileSystem filesystem, final int size) {
super(size, true);
this.filesystem = filesystem;
}
@Override
protected boolean removeLRU(final AbstractLinkedMap.LinkEntry linkEntry) {
synchronized (LRUFilesCache.this) {
final FileObject file = linkEntry.getValue();
// System.err.println(">>> " + size() + " check removeLRU:" + linkEntry.getKey().toString());
if (file.isAttached() || file.isContentOpen()) {
// do not allow open or attached files to be removed
// System.err.println(">>> " + size() + " VETO removeLRU:" +
// linkEntry.getKey().toString() + " (" + file.isAttached() + "/" +
// file.isContentOpen() + ")");
return false;
}
// System.err.println(">>> " + size() + " removeLRU:" + linkEntry.getKey().toString());
if (super.removeLRU(linkEntry)) {
try {
// force detach
file.close();
} catch (final FileSystemException e) {
VfsLog.warn(getLogger(), log, Messages.getString("vfs.impl/LRUFilesCache-remove-ex.warn"), e);
}
final Map files = filesystemCache.get(filesystem);
if (files.size() < 1) {
filesystemCache.remove(filesystem);
}
return true;
}
return false;
}
}
}
/**
* Default constructor. Uses a LRU size of 100 per file system.
*/
public LRUFilesCache() {
this(DEFAULT_LRU_SIZE);
}
/**
* Set the desired LRU size.
*
* @param lruSize the LRU size
*/
public LRUFilesCache(final int lruSize) {
this.lruSize = lruSize;
}
@Override
public void putFile(final FileObject file) {
final Map files = getOrCreateFilesystemCache(file.getFileSystem());
writeLock.lock();
try {
files.put(file.getName(), file);
} finally {
writeLock.unlock();
}
}
@Override
public boolean putFileIfAbsent(final FileObject file) {
final Map files = getOrCreateFilesystemCache(file.getFileSystem());
writeLock.lock();
try {
final FileName name = file.getName();
if (files.containsKey(name)) {
return false;
}
files.put(name, file);
return true;
} finally {
writeLock.unlock();
}
}
@Override
public FileObject getFile(final FileSystem filesystem, final FileName name) {
final Map files = getOrCreateFilesystemCache(filesystem);
readLock.lock();
try {
return files.get(name);
} finally {
readLock.unlock();
}
}
@Override
public void clear(final FileSystem filesystem) {
final Map files = getOrCreateFilesystemCache(filesystem);
writeLock.lock();
try {
files.clear();
filesystemCache.remove(filesystem);
} finally {
writeLock.unlock();
}
}
protected Map getOrCreateFilesystemCache(final FileSystem filesystem) {
Map files = filesystemCache.get(filesystem);
if (files == null) {
files = new MyLRUMap(filesystem, lruSize);
filesystemCache.putIfAbsent(filesystem, files);
}
return files;
}
@Override
public void close() {
super.close();
filesystemCache.clear();
}
@Override
public void removeFile(final FileSystem filesystem, final FileName name) {
final Map files = getOrCreateFilesystemCache(filesystem);
writeLock.lock();
try {
files.remove(name);
if (files.size() < 1) {
filesystemCache.remove(filesystem);
}
} finally {
writeLock.unlock();
}
}
@Override
public void touchFile(final FileObject file) {
// this moves the file back on top
getFile(file.getFileSystem(), file.getName());
}
}