org.apache.xml.utils.ObjectPool Maven / Gradle / Ivy
/*
* 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.
*/
/*
* $Id: ObjectPool.java 475981 2006-11-16 23:35:53Z minchau $
*/
package org.apache.xml.utils;
import java.util.ArrayList;
import org.apache.xml.res.XMLErrorResources;
import org.apache.xml.res.XMLMessages;
/**
* Pool of object of a given type to pick from to help memory usage
* @xsl.usage internal
*/
public class ObjectPool implements java.io.Serializable
{
static final long serialVersionUID = -8519013691660936643L;
/** Type of objects in this pool.
* @serial */
private final Class objectType;
/** Stack of given objects this points to.
* @serial */
private final ArrayList freeStack;
/**
* Constructor ObjectPool
*
* @param type Type of objects for this pool
*/
public ObjectPool(Class type)
{
objectType = type;
freeStack = new ArrayList();
}
/**
* Constructor ObjectPool
*
* @param className Fully qualified name of the type of objects for this pool.
*/
public ObjectPool(String className)
{
try
{
objectType = ObjectFactory.findProviderClass(
className, ObjectFactory.findClassLoader(), true);
}
catch(ClassNotFoundException cnfe)
{
throw new WrappedRuntimeException(cnfe);
}
freeStack = new ArrayList();
}
/**
* Constructor ObjectPool
*
*
* @param type Type of objects for this pool
* @param size Size of vector to allocate
*/
public ObjectPool(Class type, int size)
{
objectType = type;
freeStack = new ArrayList(size);
}
/**
* Constructor ObjectPool
*
*/
public ObjectPool()
{
objectType = null;
freeStack = new ArrayList();
}
/**
* Get an instance of the given object in this pool if available
*
*
* @return an instance of the given object if available or null
*/
public synchronized Object getInstanceIfFree()
{
// Check if the pool is empty.
if (!freeStack.isEmpty())
{
// Remove object from end of free pool.
Object result = freeStack.remove(freeStack.size() - 1);
return result;
}
return null;
}
/**
* Get an instance of the given object in this pool
*
*
* @return An instance of the given object
*/
public synchronized Object getInstance()
{
// Check if the pool is empty.
if (freeStack.isEmpty())
{
// Create a new object if so.
try
{
return objectType.newInstance();
}
catch (InstantiationException ex){}
catch (IllegalAccessException ex){}
// Throw unchecked exception for error in pool configuration.
throw new RuntimeException(XMLMessages.createXMLMessage(XMLErrorResources.ER_EXCEPTION_CREATING_POOL, null)); //"exception creating new instance for pool");
}
else
{
// Remove object from end of free pool.
Object result = freeStack.remove(freeStack.size() - 1);
return result;
}
}
/**
* Add an instance of the given object to the pool
*
*
* @param obj Object to add.
*/
public synchronized void freeInstance(Object obj)
{
// Make sure the object is of the correct type.
// Remove safety. -sb
// if (objectType.isInstance(obj))
// {
freeStack.add(obj);
// }
// else
// {
// throw new IllegalArgumentException("argument type invalid for pool");
// }
}
}