/**
* Licensed to Apereo under one or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information regarding copyright ownership. Apereo
* 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 the
* following location:
*
* <p>http://www.apache.org/licenses/LICENSE-2.0
*
* <p>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.apereo.portal.utils.threading;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import org.apache.commons.lang.Validate;
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;
/**
* Implementation of DoubleCheckedCreator that stores what it creates in a backing Map. Subclasses
* need to implement {@link #getKey(Object...)} to provide a Map key to use for the arguments and
* {@link #create(Object...)} to create new instances of the objects. <br>
* The default constructor uses a {@link ReferenceMap} with hard references to the keys
*
*/
public abstract class MapCachingDoubleCheckedCreator<K, T> extends DoubleCheckedCreator<T> {
private final Map<K, T> objectCache;
public MapCachingDoubleCheckedCreator() {
this.objectCache = new HashMap<K, T>();
}
/** @param cache The Map to store created instances in */
public MapCachingDoubleCheckedCreator(Map<K, T> cache) {
Validate.notNull(cache, "cache can not be null");
this.objectCache = cache;
}
/**
* @param cache The Map to store created instances in
* @param readWriteLock the ReadWriteLock to use for the double checked locking
*/
public MapCachingDoubleCheckedCreator(Map<K, T> cache, ReadWriteLock readWriteLock) {
super(readWriteLock);
Validate.notNull(cache, "cache can not be null");
this.objectCache = cache;
}
/** @return A read-only view of the underlying Map used to cache created objects */
public final Map<K, T> getCacheMap() {
return Collections.unmodifiableMap(this.objectCache);
}
/** Allows the object cache map to be cleared of entries */
public final void clear() {
this.writeLock.lock();
try {
this.objectCache.clear();
} finally {
this.writeLock.unlock();
}
}
/**
* @param args Optional arguments passed to {@link #get(Object...)} used to create a key
* @return The key for the specified arguments
*/
protected abstract K getKey(Object... args);
/**
* @param key The key to create the object for
* @param args The object retrieval arguments
* @return A new object instance for the key and args
*/
protected abstract T createInternal(K key, Object... args);
/* (non-Javadoc)
* @see org.apereo.portal.utils.threading.DoubleCheckedCreator#create(java.lang.Object[])
*/
@Override
protected final T create(Object... args) {
final K key = this.getKey(args);
final T value = this.createInternal(key, args);
this.objectCache.put(key, value);
return value;
}
/* (non-Javadoc)
* @see org.apereo.portal.utils.threading.DoubleCheckedCreator#retrieve(java.lang.Object[])
*/
@Override
protected final T retrieve(Object... args) {
final K key = this.getKey(args);
return this.objectCache.get(key);
}
/** @see java.lang.Object#toString() */
@Override
public String toString() {
return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
.append("objectCache", this.objectCache)
.toString();
}
}