com.sun.enterprise.admin.util.cache.AdminCacheMemStore Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2012-2017 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://oss.oracle.com/licenses/CDDL+GPL-1.1
* or LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package com.sun.enterprise.admin.util.cache;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import javax.inject.Inject;
import org.jvnet.hk2.annotations.Service;
/** In memory {@link AdminCache} containing fixed amount of items. Rotation
* is based on last update first out.
* This implementation is backgrounded by {@link AdminCacheWeakReference} and
* all non locally cached items are searched from that implementation.
*
* @author mmares
*/
public class AdminCacheMemStore implements AdminCache {
private final static class CachedItem implements Comparable {
private Object item;
private long touched;
private CachedItem(Object item) {
this.item = item;
this.touched = System.currentTimeMillis();
}
private Object getItem() {
this.touched = System.currentTimeMillis();
return this.item;
}
@Override
public int compareTo(CachedItem o) {
return (int) (this.touched - o.touched);
}
@Override
public boolean equals(Object o) {
if(o == null || !( o instanceof CachedItem))
return false;
return compareTo((CachedItem) o) == 0;
}
@Override
public int hashCode() {
return (int)touched;
}
}
private static final AdminCacheMemStore instance = new AdminCacheMemStore();
/** Maximal count of items in cache. Rotation is based on last used first
* out.
*/
private static final int MAX_CACHED_ITEMS_COUNT = 16;
private final Map cache = new HashMap(MAX_CACHED_ITEMS_COUNT + 1);
private AdminCacheWeakReference underCache = AdminCacheWeakReference.getInstance();
private AdminCacheMemStore() {
}
@Override
public A get(String key, final Class clazz) {
if (key == null || key.isEmpty()) {
throw new IllegalArgumentException("Attribute key must be unempty.");
}
if (clazz == null) {
throw new IllegalArgumentException("Attribute clazz can not be null.");
}
CachedItem ci = cache.get(key);
if (ci == null) {
A item = underCache.get(key, clazz);
if (item != null) {
putToLocalCache(key, new CachedItem(item));
}
return item;
} else {
return (A) ci.getItem();
}
}
@Override
public void put(String key, final Object data) {
underCache.put(key, data);
putToLocalCache(key, new CachedItem(data));
}
private synchronized void putToLocalCache(String key, final CachedItem ci) {
if (cache.size() >= MAX_CACHED_ITEMS_COUNT) {
CachedItem oldest = null;
Collection values = cache.values();
for (CachedItem item : values) {
if (oldest == null) {
oldest = item;
continue;
}
if (item.touched < oldest.touched) {
oldest = item;
}
}
values.remove(oldest);
}
cache.put(key, ci);
}
@Override
public boolean contains(String key) {
if (key == null || key.isEmpty()) {
throw new IllegalArgumentException("Attribute key must be unempty.");
}
CachedItem item = cache.get(key);
if (item != null) {
item.getItem(); //Just for touch
return true;
}
return underCache.contains(key);
}
@Override
public Date lastUpdated(String key) {
return underCache.lastUpdated(key);
}
public static AdminCacheMemStore getInstance() {
return instance;
}
}