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Java 1.8+ Library with tons of utility classes required in all projects
/*
* Copyright (C) 2014-2024 Philip Helger (www.helger.com)
* philip[at]helger[dot]com
*
* 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.helger.commons.pool;
import java.util.Arrays;
import java.util.concurrent.Semaphore;
import java.util.function.Supplier;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.helger.commons.ValueEnforcer;
import com.helger.commons.concurrent.SimpleLock;
import com.helger.commons.debug.GlobalDebug;
import com.helger.commons.lang.GenericReflection;
import com.helger.commons.log.ConditionalLogger;
import com.helger.commons.log.IHasConditionalLogger;
import com.helger.commons.state.ESuccess;
import com.helger.commons.string.ToStringGenerator;
/**
* A simple generic object pool with a fixed size determined in the constructor.
*
* @author Philip Helger
* @param
* The type of the objects contained in the pool.
*/
@ThreadSafe
public final class ObjectPool implements IMutableObjectPool , IHasConditionalLogger
{
private static final Logger LOGGER = LoggerFactory.getLogger (ObjectPool.class);
private static final ConditionalLogger CONDLOG = new ConditionalLogger (LOGGER, !GlobalDebug.DEFAULT_SILENT_MODE);
// Lock for this object
private final SimpleLock m_aLock = new SimpleLock ();
// The factory for creating objects
private final IObjectPoolFactory m_aFactory;
// Semaphore for the number of items
private final Semaphore m_aAvailable;
// The items itself
@GuardedBy ("m_aLock")
private final Object [] m_aItems;
// Holds the "used/unused" state, because null items may be stored
@GuardedBy ("m_aLock")
private final boolean [] m_aUsed;
/**
* @return true if logging is disabled, false if it
* is enabled.
* @since 9.4.0
*/
public static boolean isSilentMode ()
{
return CONDLOG.isDisabled ();
}
/**
* Enable or disable certain regular log messages.
*
* @param bSilentMode
* true to disable logging, false to enable
* logging
* @return The previous value of the silent mode.
* @since 9.4.0
*/
public static boolean setSilentMode (final boolean bSilentMode)
{
return !CONDLOG.setEnabled (!bSilentMode);
}
/**
* Create a new object pool for a certain amount of items and a factory that
* creates the objects on demand.
*
* @param nItemCount
* The number of items in the pool. Must be ≥ 1.
* @param aFactory
* The factory to create object. May not be null. The
* factory may not create null objects, as this leads to
* an error!
*/
public ObjectPool (@Nonnegative final int nItemCount, @Nonnull final Supplier aFactory)
{
this (nItemCount, IObjectPoolFactory.wrap (aFactory));
}
/**
* Create a new object pool for a certain amount of items and a factory that
* creates the objects on demand.
*
* @param nItemCount
* The number of items in the pool. Must be ≥ 1.
* @param aFactory
* The factory to create object. May not be null. The
* factory may not create null objects, as this leads to
* an error!
*/
public ObjectPool (@Nonnegative final int nItemCount, @Nonnull final IObjectPoolFactory aFactory)
{
ValueEnforcer.isGT0 (nItemCount, "ItemCount");
ValueEnforcer.notNull (aFactory, "Factory");
m_aAvailable = new Semaphore (nItemCount);
m_aItems = new Object [nItemCount];
m_aUsed = new boolean [nItemCount];
Arrays.fill (m_aUsed, 0, nItemCount, false);
m_aFactory = aFactory;
}
/**
* @return The maximum number of items in the pool. Always > 0.
* @see #getBorrowedObjectCount()
* @since 11.0.6
*/
@Nonnegative
public int getPoolSize ()
{
return m_aItems.length;
}
/**
* @return The number of objects currently borrowed from the pool. Something
* between 0 and {@link #getPoolSize()}
* @see #getPoolSize()
* @since 11.0.6
*/
@Nonnegative
public int getBorrowedObjectCount ()
{
return m_aItems.length - m_aAvailable.availablePermits ();
}
public void clearUnusedItems ()
{
// Reset all cached items
m_aLock.lock ();
try
{
for (int i = 0; i < m_aItems.length; ++i)
if (!m_aUsed[i])
m_aItems[i] = null;
}
finally
{
m_aLock.unlock ();
}
}
@Nullable
public DATATYPE borrowObject ()
{
// Wait for an object to be available
try
{
m_aAvailable.acquire ();
}
catch (final InterruptedException ex)
{
// In case of acquisition interruption -> return null
CONDLOG.error ("ObjectPool interrupted", ex);
Thread.currentThread ().interrupt ();
return null;
}
m_aLock.lock ();
try
{
// Find first unused item
for (int i = 0; i < m_aItems.length; ++i)
if (!m_aUsed[i])
{
final int index = i;
DATATYPE ret;
if (m_aItems[i] == null)
{
// if the object is used for the first time, create a new object
// via the factory
CONDLOG.debug ( () -> "ObjectPool creates a new object for index " + index);
m_aItems[i] = ret = m_aFactory.create ();
if (ret == null)
throw new IllegalStateException ("The factory returned a null object [1]!");
}
else
{
// An object is already existing and may be reused
CONDLOG.debug ( () -> "ObjectPool reuses object for index " + index);
ret = GenericReflection.uncheckedCast (m_aItems[i]);
if (m_aFactory.activate (ret).isFailure ())
{
// Object cannot be reused - create a new one
CONDLOG.info ( () -> "ObjectPool failed to activate object for index " + index);
m_aItems[i] = ret = m_aFactory.create ();
if (ret == null)
throw new IllegalStateException ("The factory returned a null object [2]!");
}
else
{
CONDLOG.debug ( () -> "ObjectPool successfully activated object for index " + index);
}
}
// As the last activity
m_aUsed[i] = true;
return ret;
}
throw new IllegalStateException ("Should never be reached - ObjectPool exceeds its limit. Looks like a programming error.");
}
finally
{
m_aLock.unlock ();
}
}
@Nonnull
public ESuccess returnObject (@Nonnull final DATATYPE aItem)
{
m_aLock.lock ();
try
{
for (int i = 0; i < m_aItems.length; ++i)
if (m_aUsed[i] && aItem == m_aItems[i])
{
final int index = i;
CONDLOG.debug ( () -> "ObjectPool passivates object for index " + index);
m_aFactory.passivate (aItem);
m_aUsed[i] = false;
// Okay, we have one more unused item
m_aAvailable.release ();
return ESuccess.SUCCESS;
}
CONDLOG.error ( () -> "Object " + aItem + " is not pooled!");
return ESuccess.FAILURE;
}
finally
{
m_aLock.unlock ();
}
}
@Override
public String toString ()
{
return new ToStringGenerator (this).append ("Factory", m_aFactory).getToString ();
}
}