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/*
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*
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* 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://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
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* language governing permissions and limitations under the License.
*
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* file and include the License file at packager/legal/LICENSE.txt.
*
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*
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// Portions Copyright [2018] PAyara Foundation and/or affiliates
package com.sun.enterprise.admin.util.cache;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
/** In memory {@link AdminCache} containing fixed amount of items. Rotation
* is based on last update first out.<\br>
* 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 static final 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;
}
}