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A collection of various utility classes to ease working with strings, files, command lines, XML and more.
package org.codehaus.plexus.util;
/*
* Copyright The Codehaus 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.
*/
import java.util.ArrayList;
/**
* Pools a bunch of objects . Runs a sweeper periodically to
* keep it down to size. The objects in the pool first get disposed first.
*
* @author Bert van Brakel
* @version $Id$
*/
public class SweeperPool
{
/***/
private static final boolean DEBUG = false;
/** Sweeps the pool periodically to trim it's size */
private transient Sweeper sweeper;
/** Absolute maxiumuim size of the pool.*/
private transient int maxSize;
/** The size the pool gets trimmed down to */
private transient int minSize;
/** When the sweeper runs
* and the pool is over this size, then the pool is trimmed */
private int triggerSize;
/** Holds the pooled objects */
private ArrayList pooledObjects;
/** Flag indicating this pool is shuting down */
private boolean shuttingDown = false;
//private Vector used;
/**
*
* There are a number of settings to control how the pool operates.
*
* minSize - this is the size the pool is trimmed totriggerSize - this determines if the pool is trimmed when
* the sweeper runs. If the pool size is greater or equal than this value then
* the pool is trimmed to minSize.
* maxSize - if the pool has reached this size, any objects added
* are immediatley disposed. If the pool is this size when the sweeper runs, then
* the pool is also trimmed to minSize irrespective of the triggerSize.
* sweepInterval - how often the sweeper runs. Is actually the
* time since the sweeper last finished a pass. 0 if the sweeper should not run.
*
*
*
* Any value less than 0 is automatically converted to 0
*/
public SweeperPool( int maxSize, int minSize, int intialCapacity,
int sweepInterval, int triggerSize )
{
super();
this.maxSize = saneConvert( maxSize );
this.minSize = saneConvert( minSize );
this.triggerSize = saneConvert( triggerSize );
pooledObjects = new ArrayList( intialCapacity );
//only run a sweeper if sweep interval is positive
if ( sweepInterval > 0 )
{
sweeper = new Sweeper( this, sweepInterval );
sweeper.start();
}
}
private int saneConvert( int value )
{
if ( value < 0 )
{
return 0;
}
else
{
return value;
}
}
/**
* Return the pooled object
*/
public synchronized Object get()
{
if ( ( pooledObjects.size() == 0 ) || shuttingDown )
{
return null;
}
else
{
Object obj = pooledObjects.remove( 0 );
objectRetrieved( obj );
//used.add(obj);
return obj;
}
}
/**
* Add an object to the pool
*
* @param obj the object to pool. Can be null.
*
* @return true if the object was added to the pool, false if it was disposed or null
*
*/
public synchronized boolean put( Object obj )
{
objectAdded( obj );
if ( ( obj != null ) && ( pooledObjects.size() < maxSize )
&& ( shuttingDown == false ) )
{
pooledObjects.add( obj );
return true;
}
else if ( obj != null )
{
//no longer need the object, so dispose it
objectDisposed( obj );
}
return false;
}
/**
* Return the number of pooled objects. This is never
* greater than t maximuim size of the pool
*
* @return the number of pooled objects
*/
public synchronized int getSize()
{
return pooledObjects.size();
}
/**
* Dispose of this pool. Stops the sweeper and disposes each object in the pool
*
*/
public void dispose()
{
shuttingDown = true;
if ( sweeper != null )
{
sweeper.stop();
try
{
sweeper.join();
}
catch ( InterruptedException e )
{
System.err.println( "Unexpected execption occurred: " );
e.printStackTrace();
}
}
synchronized ( this )
{
// use an array here as objects may still be being put back in the pool
// and we don't want to throw a ConcurrentModificationException
Object[] objects = pooledObjects.toArray();
for ( int i = 0; i < objects.length; i++ )
{
objectDisposed( objects[i] );
}
pooledObjects.clear();
}
}
/**
* A pool has been disposed if has been shutdown and the sweeper has completed running.
*
* @return true if the pool has been disposed, false otherwise
*/
boolean isDisposed()
{
if ( !shuttingDown )
{
return false;
}
// A null sweeper means one was never started.
if ( sweeper == null )
{
return true;
}
return sweeper.hasStopped();
}
/**
* Trim the pool down to min size
*
*/
public synchronized void trim()
{
if ( ( ( triggerSize > 0 ) && ( pooledObjects.size() >= triggerSize ) )
|| ( ( maxSize > 0 ) && ( pooledObjects.size() >= maxSize ) ) )
{
while ( pooledObjects.size() > minSize )
{
objectDisposed( pooledObjects.remove( 0 ) );
}
}
}
/**
* Override this to be notified of object disposal. Called
* after the object has been removed. Occurs when the pool
* is trimmed.
*
* @param obj
*/
public void objectDisposed( Object obj )
{
}
/**
* Override this to be notified of object addition.
* Called before object is to be added.
*
* @param obj
*/
public void objectAdded( Object obj )
{
}
/**
* Override this to be notified of object retrieval.
* Called after object removed from the pool, but
* before returned to the client.
*
* @param obj
*/
public void objectRetrieved( Object obj )
{
}
/**
* Periodically at sweepInterval goes through
* and tests if the pool should be trimmed.
*
* @author bert
*
*/
private static class Sweeper implements Runnable
{
private final transient SweeperPool pool;
private transient boolean service = false;
private final transient int sweepInterval;
private transient Thread t = null;
/**
*
*/
public Sweeper( SweeperPool pool, int sweepInterval )
{
super();
this.sweepInterval = sweepInterval;
this.pool = pool;
}
/**
* Run the seeper.
*
* @see java.lang.Runnable#run()
*/
public void run()
{
debug( "started" );
if ( sweepInterval > 0 )
{
synchronized ( this )
{
while ( service )
{
try
{
//wait specified number of seconds
//before running next sweep
wait( sweepInterval * 1000 );
}
catch ( InterruptedException e )
{
}
runSweep();
}
}
}
debug( "stopped" );
}
public void start()
{
if ( !service )
{
service = true;
t = new Thread( this );
t.setName( "Sweeper" );
t.start();
}
}
public synchronized void stop()
{
service = false;
notifyAll();
}
void join()
throws InterruptedException
{
t.join();
}
boolean hasStopped()
{
return !service && !t.isAlive();
}
private final void debug( String msg )
{
if ( DEBUG )
{
System.err.println( this + ":" + msg );
}
}
private void runSweep()
{
debug( "runningSweep. time=" + System.currentTimeMillis() );
pool.trim();
}
}
}