/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* Licensed 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 com.frameworkset.commons.pool.impl;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Stack;
import com.frameworkset.commons.pool.BaseObjectPool;
import com.frameworkset.commons.pool.ObjectPool;
import com.frameworkset.commons.pool.PoolableObjectFactory;
/**
* A simple, {@link java.util.Stack Stack}-based {@link ObjectPool} implementation.
* <p>
* Given a {@link PoolableObjectFactory}, this class will maintain
* a simple pool of instances. A finite number of "sleeping"
* or idle instances is enforced, but when the pool is
* empty, new instances are created to support the new load.
* Hence this class places no limit on the number of "active"
* instances created by the pool, but is quite useful for
* re-using <tt>Object</tt>s without introducing
* artificial limits.
*
* @author Rodney Waldhoff
* @author Dirk Verbeeck
* @version $Revision: 383290 $ $Date: 2006-03-05 02:00:15 -0500 (Sun, 05 Mar 2006) $
*/
public class StackObjectPool extends BaseObjectPool implements ObjectPool {
/**
* Create a new pool using
* no factory. Clients must first populate the pool
* using {@link #returnObject(java.lang.Object)}
* before they can be {@link #borrowObject borrowed}.
*/
public StackObjectPool() {
this((PoolableObjectFactory)null,DEFAULT_MAX_SLEEPING,DEFAULT_INIT_SLEEPING_CAPACITY);
}
/**
* Create a new pool using
* no factory. Clients must first populate the pool
* using {@link #returnObject(java.lang.Object)}
* before they can be {@link #borrowObject borrowed}.
*
* @param maxIdle cap on the number of "sleeping" instances in the pool
*/
public StackObjectPool(int maxIdle) {
this((PoolableObjectFactory)null,maxIdle,DEFAULT_INIT_SLEEPING_CAPACITY);
}
/**
* Create a new pool using
* no factory. Clients must first populate the pool
* using {@link #returnObject(java.lang.Object)}
* before they can be {@link #borrowObject borrowed}.
*
* @param maxIdle cap on the number of "sleeping" instances in the pool
* @param initIdleCapacity initial size of the pool (this specifies the size of the container,
* it does not cause the pool to be pre-populated.)
*/
public StackObjectPool(int maxIdle, int initIdleCapacity) {
this((PoolableObjectFactory)null,maxIdle,initIdleCapacity);
}
/**
* Create a new <tt>StackObjectPool</tt> using
* the specified <i>factory</i> to create new instances.
*
* @param factory the {@link PoolableObjectFactory} used to populate the pool
*/
public StackObjectPool(PoolableObjectFactory factory) {
this(factory,DEFAULT_MAX_SLEEPING,DEFAULT_INIT_SLEEPING_CAPACITY);
}
/**
* Create a new <tt>SimpleObjectPool</tt> using
* the specified <i>factory</i> to create new instances,
* capping the number of "sleeping" instances to <i>max</i>.
*
* @param factory the {@link PoolableObjectFactory} used to populate the pool
* @param maxIdle cap on the number of "sleeping" instances in the pool
*/
public StackObjectPool(PoolableObjectFactory factory, int maxIdle) {
this(factory,maxIdle,DEFAULT_INIT_SLEEPING_CAPACITY);
}
/**
* Create a new <tt>SimpleObjectPool</tt> using
* the specified <i>factory</i> to create new instances,
* capping the number of "sleeping" instances to <i>max</i>,
* and initially allocating a container capable of containing
* at least <i>init</i> instances.
*
* @param factory the {@link PoolableObjectFactory} used to populate the pool
* @param maxIdle cap on the number of "sleeping" instances in the pool
* @param initIdleCapacity initial size of the pool (this specifies the size of the container,
* it does not cause the pool to be pre-populated.)
*/
public StackObjectPool(PoolableObjectFactory factory, int maxIdle, int initIdleCapacity) {
_factory = factory;
_maxSleeping = (maxIdle < 0 ? DEFAULT_MAX_SLEEPING : maxIdle);
int initcapacity = (initIdleCapacity < 1 ? DEFAULT_INIT_SLEEPING_CAPACITY : initIdleCapacity);
_pool = new Stack();
_pool.ensureCapacity( initcapacity > _maxSleeping ? _maxSleeping : initcapacity);
}
public synchronized Object borrowObject() throws Exception {
assertOpen();
Object obj = null;
while (null == obj) {
if (!_pool.empty()) {
obj = _pool.pop();
} else {
if(null == _factory) {
throw new NoSuchElementException();
} else {
obj = _factory.makeObject();
}
}
if(null != _factory && null != obj) {
_factory.activateObject(obj);
}
if (null != _factory && null != obj && !_factory.validateObject(obj)) {
_factory.destroyObject(obj);
obj = null;
}
}
_numActive++;
return obj;
}
public synchronized void returnObject(Object obj) throws Exception {
assertOpen();
boolean success = true;
if(null != _factory) {
if(!(_factory.validateObject(obj))) {
success = false;
} else {
try {
_factory.passivateObject(obj);
} catch(Exception e) {
success = false;
}
}
}
boolean shouldDestroy = !success;
_numActive--;
if (success) {
Object toBeDestroyed = null;
if(_pool.size() >= _maxSleeping) {
shouldDestroy = true;
toBeDestroyed = _pool.remove(0); // remove the stalest object
}
_pool.push(obj);
obj = toBeDestroyed; // swap returned obj with the stalest one so it can be destroyed
}
notifyAll(); // _numActive has changed
if(shouldDestroy) { // by constructor, shouldDestroy is false when _factory is null
try {
_factory.destroyObject(obj);
} catch(Exception e) {
// ignored
}
}
}
public synchronized void invalidateObject(Object obj) throws Exception {
assertOpen();
_numActive--;
if(null != _factory ) {
_factory.destroyObject(obj);
}
notifyAll(); // _numActive has changed
}
public synchronized int getNumIdle() {
assertOpen();
return _pool.size();
}
public synchronized int getNumActive() {
assertOpen();
return _numActive;
}
public synchronized void clear() {
assertOpen();
if(null != _factory) {
Iterator it = _pool.iterator();
while(it.hasNext()) {
try {
_factory.destroyObject(it.next());
} catch(Exception e) {
// ignore error, keep destroying the rest
}
}
}
_pool.clear();
}
public synchronized void close() throws Exception {
clear();
_pool = null;
_factory = null;
super.close();
}
/**
* Create an object, and place it into the pool.
* addObject() is useful for "pre-loading" a pool with idle objects.
* @throws Exception when the {@link #_factory} has a problem creating an object.
*/
public synchronized void addObject() throws Exception {
assertOpen();
Object obj = _factory.makeObject();
_numActive++; // A little slimy - must do this because returnObject decrements it.
this.returnObject(obj);
}
public synchronized void setFactory(PoolableObjectFactory factory) throws IllegalStateException {
assertOpen();
if(0 < getNumActive()) {
throw new IllegalStateException("Objects are already active");
} else {
clear();
_factory = factory;
}
}
/** The default cap on the number of "sleeping" instances in the pool. */
protected static final int DEFAULT_MAX_SLEEPING = 8;
/**
* The default initial size of the pool
* (this specifies the size of the container, it does not
* cause the pool to be pre-populated.)
*/
protected static final int DEFAULT_INIT_SLEEPING_CAPACITY = 4;
/** My pool. */
protected Stack _pool = null;
/** My {@link PoolableObjectFactory}. */
protected PoolableObjectFactory _factory = null;
/** The cap on the number of "sleeping" instances in the pool. */
protected int _maxSleeping = DEFAULT_MAX_SLEEPING;
/** Number of object borrowed but not yet returned to the pool. */
protected int _numActive = 0;
}