/*
* JBoss DNA (http://www.jboss.org/dna)
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership. Some portions may be licensed
* to Red Hat, Inc. under one or more contributor license agreements.
* See the AUTHORS.txt file in the distribution for a full listing of
* individual contributors.
*
* JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA
* is licensed to you under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* JBoss DNA is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.dna.graph.connector.path.cache;
import java.lang.ref.SoftReference;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import net.jcip.annotations.ThreadSafe;
import org.jboss.dna.graph.connector.path.PathNode;
import org.jboss.dna.graph.property.Path;
/**
* Implementation of {@link WorkspaceCache} that stores all nodes in-memory.
*/
@ThreadSafe
public class InMemoryWorkspaceCache implements WorkspaceCache {
private final ConcurrentMap<Path, CacheEntry> nodesByPath = new ConcurrentHashMap<Path, CacheEntry>();
private PathCachePolicy policy = null;
private DefaultCacheStatistics statistics = new DefaultCacheStatistics();
public void initialize( PathCachePolicy policy,
String workspaceName ) {
if (this.policy != null) {
throw new IllegalStateException();
}
this.policy = policy;
}
protected PathCachePolicy policy() {
return policy;
}
public void clearStatistics() {
statistics = new DefaultCacheStatistics();
}
public CacheStatistics getStatistics() {
return this.statistics;
}
public PathNode get( Path path ) {
assert path != null;
CacheEntry entry = nodesByPath.get(path);
if (entry == null) {
statistics.incrementMisses();
return null;
}
PathNode node = entry.getNode();
if (node != null) {
statistics.incrementHits();
return node;
}
nodesByPath.remove(path, entry);
statistics.incrementExpirations();
return null;
}
public void set( PathNode node ) {
assert node != null;
if (!policy.shouldCache(node)) return;
statistics.incrementWrites();
nodesByPath.put(node.getPath(), new CacheEntry(node));
}
public void invalidate( Path path ) {
assert path != null;
for (Iterator<Path> iter = nodesByPath.keySet().iterator(); iter.hasNext();) {
Path key = iter.next();
if (key.isAtOrBelow(path)) {
iter.remove();
}
}
}
public void close() {
assert this.statistics != null : "Attempt to close an already-closed cache";
this.nodesByPath.clear();
this.statistics = null;
}
class CacheEntry {
private final SoftReference<PathNode> ref;
private final long expiryTime;
CacheEntry( PathNode node ) {
ref = new SoftReference<PathNode>(node);
expiryTime = System.currentTimeMillis() + (policy().getTimeToLive() * 1000);
}
PathNode getNode() {
if (System.currentTimeMillis() > expiryTime) {
return null;
}
return ref.get();
}
}
/**
* Trivial path cache policy implementation that caches all nodes in an in-memory cache.
* <p>
* As a result, this cache policy may not be safe for use with some large repositories as it does not attempt to limit cache
* attempts based on the size of the node or the current size of the cache.
* </p>
*/
public static class InMemoryCachePolicy implements PathCachePolicy {
private static final long serialVersionUID = 1L;
private final long cacheTimeToLiveInSeconds;
public InMemoryCachePolicy( long cacheTimeToLiveInSeconds ) {
super();
this.cacheTimeToLiveInSeconds = cacheTimeToLiveInSeconds;
}
/**
* @return true for all nodes
* @see PathCachePolicy#shouldCache(PathNode)
*/
public boolean shouldCache( PathNode node ) {
return true;
}
public long getTimeToLive() {
return this.cacheTimeToLiveInSeconds;
}
public Class<? extends WorkspaceCache> getCacheClass() {
return InMemoryWorkspaceCache.class;
}
}
}