PoolUtils.java
/*
* 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.
*/
package org.apache.tomcat.dbcp.pool2;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
/**
* This class consists exclusively of static methods that operate on or return
* ObjectPool or KeyedObjectPool related interfaces.
*
* @since 2.0
*/
public final class PoolUtils {
private static final String MSG_MIN_IDLE = "minIdle must be non-negative.";
public static final String MSG_NULL_KEY = "key must not be null.";
private static final String MSG_NULL_KEYED_POOL = "keyedPool must not be null.";
public static final String MSG_NULL_KEYS = "keys must not be null.";
private static final String MSG_NULL_POOL = "pool must not be null.";
/**
* Timer used to periodically check pools idle object count. Because a
* {@link Timer} creates a {@link Thread}, an IODH is used.
*/
static class TimerHolder {
static final Timer MIN_IDLE_TIMER = new Timer(true);
}
/**
* PoolUtils instances should NOT be constructed in standard programming.
* Instead, the class should be used procedurally: PoolUtils.adapt(aPool);.
* This constructor is public to permit tools that require a JavaBean
* instance to operate.
*/
public PoolUtils() {
}
/**
* Should the supplied Throwable be re-thrown (eg if it is an instance of
* one of the Throwables that should never be swallowed). Used by the pool
* error handling for operations that throw exceptions that normally need to
* be ignored.
*
* @param t
* The Throwable to check
* @throws ThreadDeath
* if that is passed in
* @throws VirtualMachineError
* if that is passed in
*/
public static void checkRethrow(final Throwable t) {
if (t instanceof ThreadDeath) {
throw (ThreadDeath) t;
}
if (t instanceof VirtualMachineError) {
throw (VirtualMachineError) t;
}
// All other instances of Throwable will be silently swallowed
}
/**
* Periodically check the idle object count for the pool. At most one idle
* object will be added per period. If there is an exception when calling
* {@link ObjectPool#addObject()} then no more checks will be performed.
*
* @param pool
* the pool to check periodically.
* @param minIdle
* if the {@link ObjectPool#getNumIdle()} is less than this then
* add an idle object.
* @param period
* the frequency to check the number of idle objects in a pool,
* see {@link Timer#schedule(TimerTask, long, long)}.
* @param <T> the type of objects in the pool
* @return the {@link TimerTask} that will periodically check the pools idle
* object count.
* @throws IllegalArgumentException
* when {@code pool} is {@code null} or when {@code minIdle} is
* negative or when {@code period} isn't valid for
* {@link Timer#schedule(TimerTask, long, long)}
*/
public static <T> TimerTask checkMinIdle(final ObjectPool<T> pool,
final int minIdle, final long period)
throws IllegalArgumentException {
if (pool == null) {
throw new IllegalArgumentException(MSG_NULL_KEYED_POOL);
}
if (minIdle < 0) {
throw new IllegalArgumentException(MSG_MIN_IDLE);
}
final TimerTask task = new ObjectPoolMinIdleTimerTask<>(pool, minIdle);
getMinIdleTimer().schedule(task, 0L, period);
return task;
}
/**
* Periodically check the idle object count for the key in the keyedPool. At
* most one idle object will be added per period. If there is an exception
* when calling {@link KeyedObjectPool#addObject(Object)} then no more
* checks for that key will be performed.
*
* @param keyedPool
* the keyedPool to check periodically.
* @param key
* the key to check the idle count of.
* @param minIdle
* if the {@link KeyedObjectPool#getNumIdle(Object)} is less than
* this then add an idle object.
* @param period
* the frequency to check the number of idle objects in a
* keyedPool, see {@link Timer#schedule(TimerTask, long, long)}.
* @param <K> the type of the pool key
* @param <V> the type of pool entries
* @return the {@link TimerTask} that will periodically check the pools idle
* object count.
* @throws IllegalArgumentException
* when {@code keyedPool}, {@code key} is {@code null} or
* when {@code minIdle} is negative or when {@code period} isn't
* valid for {@link Timer#schedule(TimerTask, long, long)}.
*/
public static <K, V> TimerTask checkMinIdle(
final KeyedObjectPool<K, V> keyedPool, final K key,
final int minIdle, final long period)
throws IllegalArgumentException {
if (keyedPool == null) {
throw new IllegalArgumentException(MSG_NULL_KEYED_POOL);
}
if (key == null) {
throw new IllegalArgumentException(MSG_NULL_KEY);
}
if (minIdle < 0) {
throw new IllegalArgumentException(MSG_MIN_IDLE);
}
final TimerTask task = new KeyedObjectPoolMinIdleTimerTask<>(
keyedPool, key, minIdle);
getMinIdleTimer().schedule(task, 0L, period);
return task;
}
/**
* Periodically check the idle object count for each key in the
* {@code Collection keys} in the keyedPool. At most one idle object will be
* added per period.
*
* @param keyedPool
* the keyedPool to check periodically.
* @param keys
* a collection of keys to check the idle object count.
* @param minIdle
* if the {@link KeyedObjectPool#getNumIdle(Object)} is less than
* this then add an idle object.
* @param period
* the frequency to check the number of idle objects in a
* keyedPool, see {@link Timer#schedule(TimerTask, long, long)}.
* @param <K> the type of the pool key
* @param <V> the type of pool entries
* @return a {@link Map} of key and {@link TimerTask} pairs that will
* periodically check the pools idle object count.
* @throws IllegalArgumentException
* when {@code keyedPool}, {@code keys}, or any of the values in
* the collection is {@code null} or when {@code minIdle} is
* negative or when {@code period} isn't valid for
* {@link Timer#schedule(TimerTask, long, long)}.
* @see #checkMinIdle(KeyedObjectPool, Object, int, long)
*/
public static <K, V> Map<K, TimerTask> checkMinIdle(
final KeyedObjectPool<K, V> keyedPool, final Collection<K> keys,
final int minIdle, final long period)
throws IllegalArgumentException {
if (keys == null) {
throw new IllegalArgumentException(MSG_NULL_KEYS);
}
final Map<K, TimerTask> tasks = new HashMap<>(keys.size());
for (K key : keys) {
final TimerTask task = checkMinIdle(keyedPool, key, minIdle, period);
tasks.put(key, task);
}
return tasks;
}
/**
* Calls {@link ObjectPool#addObject()} on {@code pool} {@code count} number
* of times.
*
* @param pool
* the pool to prefill.
* @param count
* the number of idle objects to add.
* @param <T> the type of objects in the pool
* @throws Exception
* when {@link ObjectPool#addObject()} fails.
* @throws IllegalArgumentException
* when {@code pool} is {@code null}.
* @deprecated Use {@link ObjectPool#addObjects(int)}.
*/
@Deprecated
public static <T> void prefill(final ObjectPool<T> pool, final int count)
throws Exception, IllegalArgumentException {
if (pool == null) {
throw new IllegalArgumentException(MSG_NULL_POOL);
}
pool.addObjects(count);
}
/**
* Calls {@link KeyedObjectPool#addObject(Object)} on {@code keyedPool} with
* {@code key} {@code count} number of times.
*
* @param keyedPool
* the keyedPool to prefill.
* @param key
* the key to add objects for.
* @param count
* the number of idle objects to add for {@code key}.
* @param <K> the type of the pool key
* @param <V> the type of pool entries
* @throws Exception
* when {@link KeyedObjectPool#addObject(Object)} fails.
* @throws IllegalArgumentException
* when {@code keyedPool} or {@code key} is {@code null}.
* @deprecated Use {@link KeyedObjectPool#addObjects(Object, int)}.
*/
@Deprecated
public static <K, V> void prefill(final KeyedObjectPool<K, V> keyedPool,
final K key, final int count) throws Exception,
IllegalArgumentException {
if (keyedPool == null) {
throw new IllegalArgumentException(MSG_NULL_KEYED_POOL);
}
keyedPool.addObjects(key, count);
}
/**
* Calls {@link KeyedObjectPool#addObject(Object)} on {@code keyedPool} with
* each key in {@code keys} for {@code count} number of times. This has
* the same effect as calling {@link #prefill(KeyedObjectPool, Object, int)}
* for each key in the {@code keys} collection.
*
* @param keyedPool
* the keyedPool to prefill.
* @param keys
* {@link Collection} of keys to add objects for.
* @param count
* the number of idle objects to add for each {@code key}.
* @param <K> the type of the pool key
* @param <V> the type of pool entries
* @throws Exception
* when {@link KeyedObjectPool#addObject(Object)} fails.
* @throws IllegalArgumentException
* when {@code keyedPool}, {@code keys}, or any value in
* {@code keys} is {@code null}.
* @see #prefill(KeyedObjectPool, Object, int)
* @deprecated Use {@link KeyedObjectPool#addObjects(Collection, int)}.
*/
@Deprecated
public static <K, V> void prefill(final KeyedObjectPool<K, V> keyedPool,
final Collection<K> keys, final int count) throws Exception,
IllegalArgumentException {
if (keys == null) {
throw new IllegalArgumentException(MSG_NULL_KEYS);
}
keyedPool.addObjects(keys, count);
}
/**
* Returns a synchronized (thread-safe) PooledObjectFactory backed by the
* specified PooledObjectFactory.
*
* @param factory
* the PooledObjectFactory to be "wrapped" in a synchronized
* PooledObjectFactory.
* @param <T> the type of objects in the pool
* @return a synchronized view of the specified PooledObjectFactory.
*/
public static <T> PooledObjectFactory<T> synchronizedPooledFactory(
final PooledObjectFactory<T> factory) {
return new SynchronizedPooledObjectFactory<>(factory);
}
/**
* Returns a synchronized (thread-safe) KeyedPooledObjectFactory backed by
* the specified KeyedPoolableObjectFactory.
*
* @param keyedFactory
* the KeyedPooledObjectFactory to be "wrapped" in a
* synchronized KeyedPooledObjectFactory.
* @param <K> the type of the pool key
* @param <V> the type of pool entries
* @return a synchronized view of the specified KeyedPooledObjectFactory.
*/
public static <K, V> KeyedPooledObjectFactory<K, V> synchronizedKeyedPooledFactory(
final KeyedPooledObjectFactory<K, V> keyedFactory) {
return new SynchronizedKeyedPooledObjectFactory<>(keyedFactory);
}
/**
* Gets the {@code Timer} for checking keyedPool's idle count.
*
* @return the {@link Timer} for checking keyedPool's idle count.
*/
private static Timer getMinIdleTimer() {
return TimerHolder.MIN_IDLE_TIMER;
}
/**
* Timer task that adds objects to the pool until the number of idle
* instances reaches the configured minIdle. Note that this is not the same
* as the pool's minIdle setting.
*
* @param <T> type of objects in the pool
*/
private static final class ObjectPoolMinIdleTimerTask<T> extends TimerTask {
/** Minimum number of idle instances. Not the same as pool.getMinIdle(). */
private final int minIdle;
/** Object pool */
private final ObjectPool<T> pool;
/**
* Create a new ObjectPoolMinIdleTimerTask for the given pool with the
* given minIdle setting.
*
* @param pool
* object pool
* @param minIdle
* number of idle instances to maintain
* @throws IllegalArgumentException
* if the pool is null
*/
ObjectPoolMinIdleTimerTask(final ObjectPool<T> pool, final int minIdle)
throws IllegalArgumentException {
if (pool == null) {
throw new IllegalArgumentException(MSG_NULL_POOL);
}
this.pool = pool;
this.minIdle = minIdle;
}
/**
* {@inheritDoc}
*/
@Override
public void run() {
boolean success = false;
try {
if (pool.getNumIdle() < minIdle) {
pool.addObject();
}
success = true;
} catch (final Exception e) {
cancel();
} finally {
// detect other types of Throwable and cancel this Timer
if (!success) {
cancel();
}
}
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("ObjectPoolMinIdleTimerTask");
sb.append("{minIdle=").append(minIdle);
sb.append(", pool=").append(pool);
sb.append('}');
return sb.toString();
}
}
/**
* Timer task that adds objects to the pool until the number of idle
* instances for the given key reaches the configured minIdle. Note that
* this is not the same as the pool's minIdle setting.
*
* @param <K> object pool key type
* @param <V> object pool value type
*/
private static final class KeyedObjectPoolMinIdleTimerTask<K, V> extends
TimerTask {
/** Minimum number of idle instances. Not the same as pool.getMinIdle(). */
private final int minIdle;
/** Key to ensure minIdle for */
private final K key;
/** Keyed object pool */
private final KeyedObjectPool<K, V> keyedPool;
/**
* Creates a new KeyedObjecPoolMinIdleTimerTask.
*
* @param keyedPool
* keyed object pool
* @param key
* key to ensure minimum number of idle instances
* @param minIdle
* minimum number of idle instances
* @throws IllegalArgumentException
* if the key is null
*/
KeyedObjectPoolMinIdleTimerTask(final KeyedObjectPool<K, V> keyedPool,
final K key, final int minIdle) throws IllegalArgumentException {
if (keyedPool == null) {
throw new IllegalArgumentException(
MSG_NULL_KEYED_POOL);
}
this.keyedPool = keyedPool;
this.key = key;
this.minIdle = minIdle;
}
/**
* {@inheritDoc}
*/
@Override
public void run() {
boolean success = false;
try {
if (keyedPool.getNumIdle(key) < minIdle) {
keyedPool.addObject(key);
}
success = true;
} catch (final Exception e) {
cancel();
} finally {
// detect other types of Throwable and cancel this Timer
if (!success) {
cancel();
}
}
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("KeyedObjectPoolMinIdleTimerTask");
sb.append("{minIdle=").append(minIdle);
sb.append(", key=").append(key);
sb.append(", keyedPool=").append(keyedPool);
sb.append('}');
return sb.toString();
}
}
/**
* A fully synchronized PooledObjectFactory that wraps a
* PooledObjectFactory and synchronizes access to the wrapped factory
* methods.
* <p>
* <b>Note:</b> This should not be used on pool implementations that already
* provide proper synchronization such as the pools provided in the Commons
* Pool library.
* </p>
*
* @param <T> pooled object factory type
*/
private static final class SynchronizedPooledObjectFactory<T> implements
PooledObjectFactory<T> {
/** Synchronization lock */
private final WriteLock writeLock = new ReentrantReadWriteLock().writeLock();
/** Wrapped factory */
private final PooledObjectFactory<T> factory;
/**
* Creates a SynchronizedPoolableObjectFactory wrapping the given
* factory.
*
* @param factory
* underlying factory to wrap
* @throws IllegalArgumentException
* if the factory is null
*/
SynchronizedPooledObjectFactory(final PooledObjectFactory<T> factory)
throws IllegalArgumentException {
if (factory == null) {
throw new IllegalArgumentException("factory must not be null.");
}
this.factory = factory;
}
/**
* {@inheritDoc}
*/
@Override
public PooledObject<T> makeObject() throws Exception {
writeLock.lock();
try {
return factory.makeObject();
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void destroyObject(final PooledObject<T> p) throws Exception {
writeLock.lock();
try {
factory.destroyObject(p);
} finally {
writeLock.unlock();
}
}
@Override
public void destroyObject(PooledObject<T> p, DestroyMode mode) throws Exception {
destroyObject(p);
}
/**
* {@inheritDoc}
*/
@Override
public boolean validateObject(final PooledObject<T> p) {
writeLock.lock();
try {
return factory.validateObject(p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void activateObject(final PooledObject<T> p) throws Exception {
writeLock.lock();
try {
factory.activateObject(p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void passivateObject(final PooledObject<T> p) throws Exception {
writeLock.lock();
try {
factory.passivateObject(p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("SynchronizedPoolableObjectFactory");
sb.append("{factory=").append(factory);
sb.append('}');
return sb.toString();
}
}
/**
* A fully synchronized KeyedPooledObjectFactory that wraps a
* KeyedPooledObjectFactory and synchronizes access to the wrapped factory
* methods.
* <p>
* <b>Note:</b> This should not be used on pool implementations that already
* provide proper synchronization such as the pools provided in the Commons
* Pool library.
* </p>
*
* @param <K> pooled object factory key type
* @param <V> pooled object factory key value
*/
private static final class SynchronizedKeyedPooledObjectFactory<K, V>
implements KeyedPooledObjectFactory<K, V> {
/** Synchronization lock */
private final WriteLock writeLock = new ReentrantReadWriteLock().writeLock();
/** Wrapped factory */
private final KeyedPooledObjectFactory<K, V> keyedFactory;
/**
* Creates a SynchronizedKeyedPoolableObjectFactory wrapping the given
* factory.
*
* @param keyedFactory
* underlying factory to wrap
* @throws IllegalArgumentException
* if the factory is null
*/
SynchronizedKeyedPooledObjectFactory(
final KeyedPooledObjectFactory<K, V> keyedFactory)
throws IllegalArgumentException {
if (keyedFactory == null) {
throw new IllegalArgumentException(
"keyedFactory must not be null.");
}
this.keyedFactory = keyedFactory;
}
/**
* {@inheritDoc}
*/
@Override
public PooledObject<V> makeObject(final K key) throws Exception {
writeLock.lock();
try {
return keyedFactory.makeObject(key);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void destroyObject(final K key, final PooledObject<V> p) throws Exception {
writeLock.lock();
try {
keyedFactory.destroyObject(key, p);
} finally {
writeLock.unlock();
}
}
@Override
public void destroyObject(K key, PooledObject<V> p, DestroyMode mode) throws Exception {
destroyObject(key, p);
}
/**
* {@inheritDoc}
*/
@Override
public boolean validateObject(final K key, final PooledObject<V> p) {
writeLock.lock();
try {
return keyedFactory.validateObject(key, p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void activateObject(final K key, final PooledObject<V> p) throws Exception {
writeLock.lock();
try {
keyedFactory.activateObject(key, p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public void passivateObject(final K key, final PooledObject<V> p) throws Exception {
writeLock.lock();
try {
keyedFactory.passivateObject(key, p);
} finally {
writeLock.unlock();
}
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
sb.append("SynchronizedKeyedPoolableObjectFactory");
sb.append("{keyedFactory=").append(keyedFactory);
sb.append('}');
return sb.toString();
}
}
}