/**
* 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.lucene.gdata.utils;
import java.util.Stack;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* A Simple implementation of the {@link org.apache.lucene.gdata.utils.Pool}
* interface using a {@link java.util.Stack} as a buffer for the pooled objects.
* This implementation does not provide any timeout mechanismn. Objects will
* stay inside the pool until the pool is destroyed.
* <p>
* If any object will be released e.g. handover to the pool and the pool has
* already enought objects in the pool the released object will be destroyed. If
* the pool is empty a new Object will be created.
* </p>
* <p>
* This implementation does not track any references to the objects aquired by
* any other resource. The objects must be destroyed manually if not released to
* the pool after aquired.
* </p>
*
* @author Simon Willnauer
* @param <Type>
*
*/
public class SimpleObjectPool<Type> implements Pool<Type> {
private static final Log LOG = LogFactory.getLog(SimpleObjectPool.class);
private volatile boolean isDestroyed = false;
private final PoolObjectFactory<Type> factory;
static final int DEFAULTSIZE = 5;
static final int MINIMALSIZE = 1;
private final int size;
private final Stack<Type> pool;
private final ReentrantReadWriteLock masterLock = new ReentrantReadWriteLock();
private final Lock readLock = this.masterLock.readLock();
private final Lock writeLock = this.masterLock.writeLock();
/**
* Constructs a new {@link SimpleObjectPool} and sets the ObjectFactory and the pool size
* @param size - the maximum size of the pool
* @param factory - factory to create and destroy pooled objects
*
*/
public SimpleObjectPool(int size, PoolObjectFactory<Type> factory) {
if (factory == null)
throw new IllegalArgumentException("Factory must not be null");
this.factory = factory;
this.size = size < MINIMALSIZE ? MINIMALSIZE : size;
this.pool = new Stack<Type>();
for (int i = 0; i < this.size; i++) {
this.pool.push(this.factory.getInstance());
}
}
/**
* @param factory
*/
public SimpleObjectPool(PoolObjectFactory<Type> factory) {
this(DEFAULTSIZE,factory);
}
/**
* @see org.apache.lucene.gdata.utils.Pool#aquire()
*/
public Type aquire() {
// fail if writelock is aquired
if (this.readLock.tryLock()) {
try {
if (this.isDestroyed)
throw new IllegalStateException(
"The pool has already been closed");
if (this.pool.isEmpty())
return this.factory.getInstance();
return this.pool.pop();
} finally {
this.readLock.unlock();
}
}
throw new IllegalStateException("The pool has already been closed");
}
/**
*
* @param type - generic type
* @see org.apache.lucene.gdata.utils.Pool#release(Object)
*/
public void release(Type type) {
// fail if writelock is aquired
if (this.readLock.tryLock()) {
try {
if (this.pool.size() < this.size && !this.isDestroyed)
this.pool.push(type);
else
this.factory.destroyInstance(type);
} finally {
this.readLock.unlock();
}
return;
}
// enable object need to be destoryed
this.factory.destroyInstance(type);
}
/**
* @see org.apache.lucene.gdata.utils.Pool#getSize()
*/
public int getSize() {
return this.size;
}
/**
* @see org.apache.lucene.gdata.utils.Pool#getExpireTime()
*/
public long getExpireTime() {
return 0;
}
/**
* @see org.apache.lucene.gdata.utils.Pool#expires()
*/
public boolean expires() {
return false;
}
/**
* @see org.apache.lucene.gdata.utils.Pool#destroy()
*/
public void destroy() {
this.writeLock.lock();
try {
if (this.isDestroyed)
return;
this.isDestroyed = true;
LOG.info("Destroy all elements in the pool -- poolsize: "+this.pool.size());
for (Type type : this.pool) {
this.factory.destroyInstance(type);
}
this.pool.clear();
} finally {
this.writeLock.unlock();
}
}
}
|