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471 lines
19 KiB
471 lines
19 KiB
/* |
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* Licensed to the Apache Software Foundation (ASF) under one or more |
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* contributor license agreements. See the NOTICE file distributed with |
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* this work for additional information regarding copyright ownership. |
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* The ASF licenses this file to You under the Apache License, Version 2.0 |
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* (the "License"); you may not use this file except in compliance with |
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* the License. You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package com.fr.third.org.apache.commons.pool.impl; |
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import java.util.Iterator; |
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import java.util.NoSuchElementException; |
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import java.util.Stack; |
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import com.fr.third.org.apache.commons.pool.BaseObjectPool; |
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import com.fr.third.org.apache.commons.pool.ObjectPool; |
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import com.fr.third.org.apache.commons.pool.PoolUtils; |
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import com.fr.third.org.apache.commons.pool.PoolableObjectFactory; |
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/** |
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* A simple, {@link java.util.Stack Stack}-based {@link ObjectPool} implementation. |
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* <p> |
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* Given a {@link PoolableObjectFactory}, this class will maintain |
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* a simple pool of instances. A finite number of "sleeping" |
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* or idle instances is enforced, but when the pool is |
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* empty, new instances are created to support the new load. |
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* Hence this class places no limit on the number of "active" |
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* instances created by the pool, but is quite useful for |
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* re-using <tt>Object</tt>s without introducing |
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* artificial limits. |
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* |
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* @param <T> the type of objects held in this pool |
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* |
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* @author Rodney Waldhoff |
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* @author Dirk Verbeeck |
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* @author Sandy McArthur |
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* @version $Revision$ $Date$ |
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* @since Pool 1.0 |
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*/ |
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public class StackObjectPool<T> extends BaseObjectPool<T> implements ObjectPool<T> { |
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/** |
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* Create a new pool using no factory. Clients must first |
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* {@link #setFactory(PoolableObjectFactory) set the factory} or |
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* else this pool will not behave correctly. Clients may first populate the pool |
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* using {@link #returnObject(java.lang.Object)} before they can be {@link #borrowObject borrowed} |
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* but this usage is <strong>discouraged</strong>. |
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* |
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* @see #StackObjectPool(PoolableObjectFactory) |
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* @deprecated to be removed in pool 2.0 - use {@link #StackObjectPool(PoolableObjectFactory)} |
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*/ |
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@Deprecated |
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public StackObjectPool() { |
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this(null,DEFAULT_MAX_SLEEPING,DEFAULT_INIT_SLEEPING_CAPACITY); |
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} |
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/** |
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* Create a new pool using no factory. |
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* Clients must first {@link #setFactory(PoolableObjectFactory) set the factory} or |
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* else this pool will not behave correctly. Clients may first populate the pool |
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* using {@link #returnObject(java.lang.Object)} before they can be {@link #borrowObject borrowed} |
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* but this usage is <strong>discouraged</strong>. |
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* |
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* @param maxIdle cap on the number of "sleeping" instances in the pool |
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* @see #StackObjectPool(PoolableObjectFactory, int) |
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* @deprecated to be removed in pool 2.0 - use {@link #StackObjectPool(PoolableObjectFactory, int)} |
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*/ |
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@Deprecated |
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public StackObjectPool(int maxIdle) { |
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this(null,maxIdle,DEFAULT_INIT_SLEEPING_CAPACITY); |
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} |
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/** |
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* Create a new pool using no factory. |
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* Clients must first {@link #setFactory(PoolableObjectFactory) set the factory} or |
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* else this pool will not behave correctly. Clients may first populate the pool |
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* using {@link #returnObject(java.lang.Object)} before they can be {@link #borrowObject borrowed} |
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* but this usage is <strong>discouraged</strong>. |
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* |
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* @param maxIdle cap on the number of "sleeping" instances in the pool |
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* @param initIdleCapacity initial size of the pool (this specifies the size of the container, |
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* it does not cause the pool to be pre-populated.) |
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* @see #StackObjectPool(PoolableObjectFactory, int, int) |
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* @deprecated to be removed in pool 2.0 - use {@link #StackObjectPool(PoolableObjectFactory, int, int)} |
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*/ |
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@Deprecated |
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public StackObjectPool(int maxIdle, int initIdleCapacity) { |
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this(null,maxIdle,initIdleCapacity); |
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} |
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/** |
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* Create a new <tt>StackObjectPool</tt> using the specified <i>factory</i> to create new instances. |
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* |
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* @param factory the {@link PoolableObjectFactory} used to populate the pool |
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*/ |
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public StackObjectPool(PoolableObjectFactory<T> factory) { |
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this(factory,DEFAULT_MAX_SLEEPING,DEFAULT_INIT_SLEEPING_CAPACITY); |
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} |
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/** |
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* Create a new <tt>SimpleObjectPool</tt> using the specified <i>factory</i> to create new instances, |
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* capping the number of "sleeping" instances to <i>maxIdle</i>. |
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* |
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* @param factory the {@link PoolableObjectFactory} used to populate the pool |
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* @param maxIdle cap on the number of "sleeping" instances in the pool |
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*/ |
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public StackObjectPool(PoolableObjectFactory<T> factory, int maxIdle) { |
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this(factory,maxIdle,DEFAULT_INIT_SLEEPING_CAPACITY); |
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} |
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/** |
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* <p>Create a new <tt>StackObjectPool</tt> using the specified <code>factory</code> to create new instances, |
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* capping the number of "sleeping" instances to <code>maxIdle</code>, and initially allocating a container |
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* capable of containing at least <code>initIdleCapacity</code> instances. The pool is not pre-populated. |
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* The <code>initIdleCapacity</code> parameter just determines the initial size of the underlying |
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* container, which can increase beyond this value if <code>maxIdle > initIdleCapacity.</code></p> |
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* |
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* <p>Negative values of <code>maxIdle</code> are ignored (i.e., the pool is created using |
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* {@link #DEFAULT_MAX_SLEEPING}) as are non-positive values for <code>initIdleCapacity.</code> |
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* |
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* @param factory the {@link PoolableObjectFactory} used to populate the pool |
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* @param maxIdle cap on the number of "sleeping" instances in the pool |
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* @param initIdleCapacity initial size of the pool (this specifies the size of the container, |
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* it does not cause the pool to be pre-populated.) |
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*/ |
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public StackObjectPool(PoolableObjectFactory<T> factory, int maxIdle, int initIdleCapacity) { |
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_factory = factory; |
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_maxSleeping = (maxIdle < 0 ? DEFAULT_MAX_SLEEPING : maxIdle); |
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int initcapacity = (initIdleCapacity < 1 ? DEFAULT_INIT_SLEEPING_CAPACITY : initIdleCapacity); |
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_pool = new Stack<T>(); |
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_pool.ensureCapacity( initcapacity > _maxSleeping ? _maxSleeping : initcapacity); |
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} |
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/** |
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* <p>Borrows an object from the pool. If there are idle instances available on the stack, |
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* the top element of the stack is popped to activate, validate and return to the client. If there |
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* are no idle instances available, the {@link PoolableObjectFactory#makeObject() makeObject} |
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* method of the pool's {@link PoolableObjectFactory} is invoked to create a new instance.</p> |
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* |
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* <p>All instances are {@link PoolableObjectFactory#activateObject(Object) activated} and |
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* {@link PoolableObjectFactory#validateObject(Object) validated} before being returned to the |
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* client. If validation fails or an exception occurs activating or validating an instance |
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* popped from the idle instance stack, the failing instance is |
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* {@link PoolableObjectFactory#destroyObject(Object) destroyed} and the next instance on |
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* the stack is popped, validated and activated. This process continues until either the |
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* stack is empty or an instance passes validation. If the stack is empty on activation or |
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* it does not contain any valid instances, the factory's <code>makeObject</code> method is used |
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* to create a new instance. If a null instance is returned by the factory or the created |
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* instance either raises an exception on activation or fails validation, <code>NoSuchElementException</code> |
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* is thrown. Exceptions thrown by <code>MakeObject</code> are propagated to the caller; but |
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* other than <code>ThreadDeath</code> or <code>VirtualMachineError</code>, exceptions generated by |
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* activation, validation or destroy methods are swallowed silently.</p> |
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* |
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* @return an instance from the pool |
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*/ |
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@Override |
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public synchronized T borrowObject() throws Exception { |
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assertOpen(); |
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T obj = null; |
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boolean newlyCreated = false; |
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while (null == obj) { |
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if (!_pool.empty()) { |
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obj = _pool.pop(); |
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} else { |
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if(null == _factory) { |
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throw new NoSuchElementException(); |
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} else { |
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obj = _factory.makeObject(); |
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newlyCreated = true; |
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if (obj == null) { |
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throw new NoSuchElementException("PoolableObjectFactory.makeObject() returned null."); |
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} |
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} |
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} |
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if (null != _factory && null != obj) { |
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try { |
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_factory.activateObject(obj); |
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if (!_factory.validateObject(obj)) { |
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throw new Exception("ValidateObject failed"); |
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} |
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} catch (Throwable t) { |
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PoolUtils.checkRethrow(t); |
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try { |
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_factory.destroyObject(obj); |
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} catch (Throwable t2) { |
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PoolUtils.checkRethrow(t2); |
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// swallowed |
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} finally { |
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obj = null; |
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} |
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if (newlyCreated) { |
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throw new NoSuchElementException( |
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"Could not create a validated object, cause: " + |
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t.getMessage()); |
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} |
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} |
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} |
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} |
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_numActive++; |
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return obj; |
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} |
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/** |
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* <p>Returns an instance to the pool, pushing it on top of the idle instance stack after successful |
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* validation and passivation. The returning instance is destroyed if any of the following are true:<ul> |
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* <li>the pool is closed</li> |
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* <li>{@link PoolableObjectFactory#validateObject(Object) validation} fails</li> |
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* <li>{@link PoolableObjectFactory#passivateObject(Object) passivation} throws an exception</li> |
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* </ul> |
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* If adding a validated, passivated returning instance to the stack would cause |
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* {@link #getMaxSleeping() maxSleeping} to be exceeded, the oldest (bottom) instance on the stack |
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* is destroyed to make room for the returning instance, which is pushed on top of the stack.</p> |
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* |
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* <p>Exceptions passivating or destroying instances are silently swallowed. Exceptions validating |
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* instances are propagated to the client.</p> |
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* |
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* @param obj instance to return to the pool |
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*/ |
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@Override |
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public synchronized void returnObject(T obj) throws Exception { |
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boolean success = !isClosed(); |
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if(null != _factory) { |
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if(!_factory.validateObject(obj)) { |
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success = false; |
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} else { |
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try { |
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_factory.passivateObject(obj); |
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} catch(Exception e) { |
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success = false; |
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} |
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} |
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} |
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boolean shouldDestroy = !success; |
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_numActive--; |
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if (success) { |
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T toBeDestroyed = null; |
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if(_pool.size() >= _maxSleeping) { |
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shouldDestroy = true; |
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toBeDestroyed = _pool.remove(0); // remove the stalest object |
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} |
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_pool.push(obj); |
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obj = toBeDestroyed; // swap returned obj with the stalest one so it can be destroyed |
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} |
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notifyAll(); // _numActive has changed |
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if(shouldDestroy) { // by constructor, shouldDestroy is false when _factory is null |
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try { |
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_factory.destroyObject(obj); |
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} catch(Exception e) { |
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// ignored |
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} |
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} |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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@Override |
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public synchronized void invalidateObject(T obj) throws Exception { |
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_numActive--; |
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if (null != _factory) { |
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_factory.destroyObject(obj); |
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} |
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notifyAll(); // _numActive has changed |
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} |
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/** |
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* Return the number of instances |
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* currently idle in this pool. |
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* |
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* @return the number of instances currently idle in this pool |
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*/ |
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@Override |
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public synchronized int getNumIdle() { |
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return _pool.size(); |
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} |
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/** |
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* Return the number of instances currently borrowed from this pool. |
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* |
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* @return the number of instances currently borrowed from this pool |
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*/ |
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@Override |
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public synchronized int getNumActive() { |
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return _numActive; |
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} |
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/** |
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* Clears any objects sitting idle in the pool. Silently swallows any |
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* exceptions thrown by {@link PoolableObjectFactory#destroyObject(Object)}. |
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*/ |
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@Override |
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public synchronized void clear() { |
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if(null != _factory) { |
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Iterator<T> it = _pool.iterator(); |
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while(it.hasNext()) { |
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try { |
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_factory.destroyObject(it.next()); |
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} catch(Exception e) { |
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// ignore error, keep destroying the rest |
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} |
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} |
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} |
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_pool.clear(); |
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} |
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/** |
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* <p>Close this pool, and free any resources associated with it. Invokes |
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* {@link #clear()} to destroy and remove instances in the pool.</p> |
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* |
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* <p>Calling {@link #addObject} or {@link #borrowObject} after invoking |
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* this method on a pool will cause them to throw an |
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* {@link IllegalStateException}.</p> |
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* |
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* @throws Exception never - exceptions clearing the pool are swallowed |
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*/ |
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@Override |
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public void close() throws Exception { |
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super.close(); |
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clear(); |
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} |
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/** |
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* <p>Create an object, and place it on top of the stack. |
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* This method is useful for "pre-loading" a pool with idle objects.</p> |
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* |
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* <p>Before being added to the pool, the newly created instance is |
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* {@link PoolableObjectFactory#validateObject(Object) validated} and |
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* {@link PoolableObjectFactory#passivateObject(Object) passivated}. If validation |
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* fails, the new instance is {@link PoolableObjectFactory#destroyObject(Object) destroyed}. |
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* Exceptions generated by the factory <code>makeObject</code> or <code>passivate</code> are |
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* propagated to the caller. Exceptions destroying instances are silently swallowed.</p> |
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* |
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* <p>If a new instance is created and successfully validated and passivated and adding this |
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* instance to the pool causes {@link #getMaxSleeping() maxSleeping} to be exceeded, the oldest |
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* (bottom) instance in the pool is destroyed to make room for the newly created instance, which |
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* is pushed on top of the stack. |
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* |
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* @throws Exception when the {@link #getFactory() factory} has a problem creating or passivating an object. |
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*/ |
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@Override |
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public synchronized void addObject() throws Exception { |
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assertOpen(); |
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if (_factory == null) { |
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throw new IllegalStateException("Cannot add objects without a factory."); |
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} |
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T obj = _factory.makeObject(); |
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boolean success = true; |
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if(!_factory.validateObject(obj)) { |
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success = false; |
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} else { |
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_factory.passivateObject(obj); |
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} |
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boolean shouldDestroy = !success; |
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if (success) { |
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T toBeDestroyed = null; |
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if(_pool.size() >= _maxSleeping) { |
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shouldDestroy = true; |
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toBeDestroyed = _pool.remove(0); // remove the stalest object |
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} |
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_pool.push(obj); |
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obj = toBeDestroyed; // swap returned obj with the stalest one so it can be destroyed |
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} |
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notifyAll(); // _numIdle has changed |
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if(shouldDestroy) { // by constructor, shouldDestroy is false when _factory is null |
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try { |
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_factory.destroyObject(obj); |
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} catch(Exception e) { |
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// ignored |
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} |
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} |
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} |
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/** |
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* Sets the {@link PoolableObjectFactory factory} this pool uses |
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* to create new instances. Trying to change |
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* the <code>factory</code> while there are borrowed objects will |
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* throw an {@link IllegalStateException}. |
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* |
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* @param factory the {@link PoolableObjectFactory} used to create new instances. |
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* @throws IllegalStateException when the factory cannot be set at this time |
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* @deprecated to be removed in pool 2.0 |
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*/ |
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@Deprecated |
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@Override |
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public synchronized void setFactory(PoolableObjectFactory<T> factory) throws IllegalStateException { |
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assertOpen(); |
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if(0 < getNumActive()) { |
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throw new IllegalStateException("Objects are already active"); |
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} else { |
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clear(); |
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_factory = factory; |
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} |
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} |
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/** |
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* The cap on the number of "sleeping" instances in the pool. |
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*/ |
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protected static final int DEFAULT_MAX_SLEEPING = 8; |
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/** |
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* The default initial size of the pool |
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* (this specifies the size of the container, it does not |
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* cause the pool to be pre-populated.) |
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*/ |
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protected static final int DEFAULT_INIT_SLEEPING_CAPACITY = 4; |
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/** |
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* My pool. |
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* @deprecated to be made private in pool 2.0 |
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*/ |
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@Deprecated |
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protected Stack<T> _pool = null; |
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/** |
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* My {@link PoolableObjectFactory}. |
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* @deprecated to be made private in pool 2.0 - use {@link #getFactory()} |
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*/ |
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@Deprecated |
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protected PoolableObjectFactory<T> _factory = null; |
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/** |
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* The cap on the number of "sleeping" instances in the pool. |
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* @deprecated to be made private in pool 2.0 - use {@link #getMaxSleeping()} |
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*/ |
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@Deprecated |
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protected int _maxSleeping = DEFAULT_MAX_SLEEPING; |
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/** |
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* Number of objects borrowed but not yet returned to the pool. |
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* @deprecated to be made private in pool 2.0 - use {@link #getNumActive()} |
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*/ |
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@Deprecated |
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protected int _numActive = 0; |
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/** |
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* Returns the {@link PoolableObjectFactory} used by this pool to create and manage object instances. |
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* |
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* @return the factory |
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* @since 1.5.5 |
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*/ |
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public synchronized PoolableObjectFactory<T> getFactory() { |
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return _factory; |
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} |
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/** |
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* Returns the maximum number of idle instances in the pool. |
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* |
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* @return maxSleeping |
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* @since 1.5.5 |
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*/ |
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public int getMaxSleeping() { |
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return _maxSleeping; |
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} |
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}
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