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Apache Commons Object Pooling Library
/*
* 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.commons.pool2.impl;
import org.apache.commons.pool2.PooledObject;
import org.apache.commons.pool2.PooledObjectState;
import org.apache.commons.pool2.TrackedUse;
import java.io.PrintWriter;
import java.util.Deque;
/**
* This wrapper is used to track the additional information, such as state, for
* the pooled objects.
*
* This class is intended to be thread-safe.
*
*
* @param the type of object in the pool
*
* @since 2.0
*/
public class DefaultPooledObject implements PooledObject {
private final T object;
private PooledObjectState state = PooledObjectState.IDLE; // @GuardedBy("this") to ensure transitions are valid
private final long createTime = System.currentTimeMillis();
private volatile long lastBorrowTime = createTime;
private volatile long lastUseTime = createTime;
private volatile long lastReturnTime = createTime;
private volatile boolean logAbandoned = false;
private volatile CallStack borrowedBy = NoOpCallStack.INSTANCE;
private volatile CallStack usedBy = NoOpCallStack.INSTANCE;
private volatile long borrowedCount = 0;
/**
* Creates a new instance that wraps the provided object so that the pool can
* track the state of the pooled object.
*
* @param object The object to wrap
*/
public DefaultPooledObject(final T object) {
this.object = object;
}
@Override
public T getObject() {
return object;
}
@Override
public long getCreateTime() {
return createTime;
}
@Override
public long getActiveTimeMillis() {
// Take copies to avoid threading issues
final long rTime = lastReturnTime;
final long bTime = lastBorrowTime;
if (rTime > bTime) {
return rTime - bTime;
}
return System.currentTimeMillis() - bTime;
}
@Override
public long getIdleTimeMillis() {
final long elapsed = System.currentTimeMillis() - lastReturnTime;
// elapsed may be negative if:
// - another thread updates lastReturnTime during the calculation window
// - System.currentTimeMillis() is not monotonic (e.g. system time is set back)
return elapsed >= 0 ? elapsed : 0;
}
@Override
public long getLastBorrowTime() {
return lastBorrowTime;
}
@Override
public long getLastReturnTime() {
return lastReturnTime;
}
/**
* Gets the number of times this object has been borrowed.
* @return The number of times this object has been borrowed.
* @since 2.1
*/
@Override
public long getBorrowedCount() {
return borrowedCount;
}
/**
* Returns an estimate of the last time this object was used. If the class
* of the pooled object implements {@link TrackedUse}, what is returned is
* the maximum of {@link TrackedUse#getLastUsed()} and
* {@link #getLastBorrowTime()}; otherwise this method gives the same
* value as {@link #getLastBorrowTime()}.
*
* @return the last time this object was used
*/
@Override
public long getLastUsedTime() {
if (object instanceof TrackedUse) {
return Math.max(((TrackedUse) object).getLastUsed(), lastUseTime);
}
return lastUseTime;
}
@Override
public int compareTo(final PooledObject other) {
final long lastActiveDiff = this.getLastReturnTime() - other.getLastReturnTime();
if (lastActiveDiff == 0) {
// Make sure the natural ordering is broadly consistent with equals
// although this will break down if distinct objects have the same
// identity hash code.
// see java.lang.Comparable Javadocs
return System.identityHashCode(this) - System.identityHashCode(other);
}
// handle int overflow
return (int)Math.min(Math.max(lastActiveDiff, Integer.MIN_VALUE), Integer.MAX_VALUE);
}
@Override
public String toString() {
final StringBuilder result = new StringBuilder();
result.append("Object: ");
result.append(object.toString());
result.append(", State: ");
synchronized (this) {
result.append(state.toString());
}
return result.toString();
// TODO add other attributes
}
@Override
public synchronized boolean startEvictionTest() {
if (state == PooledObjectState.IDLE) {
state = PooledObjectState.EVICTION;
return true;
}
return false;
}
@Override
public synchronized boolean endEvictionTest(
final Deque> idleQueue) {
if (state == PooledObjectState.EVICTION) {
state = PooledObjectState.IDLE;
return true;
} else if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
state = PooledObjectState.IDLE;
if (!idleQueue.offerFirst(this)) {
// TODO - Should never happen
}
}
return false;
}
/**
* Allocates the object.
*
* @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
*/
@Override
public synchronized boolean allocate() {
if (state == PooledObjectState.IDLE) {
state = PooledObjectState.ALLOCATED;
lastBorrowTime = System.currentTimeMillis();
lastUseTime = lastBorrowTime;
borrowedCount++;
if (logAbandoned) {
borrowedBy.fillInStackTrace();
}
return true;
} else if (state == PooledObjectState.EVICTION) {
// TODO Allocate anyway and ignore eviction test
state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
return false;
}
// TODO if validating and testOnBorrow == true then pre-allocate for
// performance
return false;
}
/**
* Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
* if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}
* or {@link PooledObjectState#RETURNING RETURNING}.
*
* @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
* or {@link PooledObjectState#RETURNING RETURNING}.
*/
@Override
public synchronized boolean deallocate() {
if (state == PooledObjectState.ALLOCATED ||
state == PooledObjectState.RETURNING) {
state = PooledObjectState.IDLE;
lastReturnTime = System.currentTimeMillis();
borrowedBy.clear();
return true;
}
return false;
}
/**
* Sets the state to {@link PooledObjectState#INVALID INVALID}
*/
@Override
public synchronized void invalidate() {
state = PooledObjectState.INVALID;
}
@Override
public void use() {
lastUseTime = System.currentTimeMillis();
usedBy.fillInStackTrace();
}
@Override
public void printStackTrace(final PrintWriter writer) {
boolean written = borrowedBy.printStackTrace(writer);
written |= usedBy.printStackTrace(writer);
if (written) {
writer.flush();
}
}
/**
* Returns the state of this object.
* @return state
*/
@Override
public synchronized PooledObjectState getState() {
return state;
}
/**
* Marks the pooled object as abandoned.
*/
@Override
public synchronized void markAbandoned() {
state = PooledObjectState.ABANDONED;
}
/**
* Marks the object as returning to the pool.
*/
@Override
public synchronized void markReturning() {
state = PooledObjectState.RETURNING;
}
@Override
public void setLogAbandoned(final boolean logAbandoned) {
this.logAbandoned = logAbandoned;
}
/**
* Configures the stack trace generation strategy based on whether or not fully
* detailed stack traces are required. When set to false, abandoned logs may
* only include caller class information rather than method names, line numbers,
* and other normal metadata available in a full stack trace.
*
* @param requireFullStackTrace the new configuration setting for abandoned object
* logging
* @since 2.5
*/
@Override
public void setRequireFullStackTrace(final boolean requireFullStackTrace) {
borrowedBy = CallStackUtils.newCallStack("'Pooled object created' " +
"yyyy-MM-dd HH:mm:ss Z 'by the following code has not been returned to the pool:'",
true, requireFullStackTrace);
usedBy = CallStackUtils.newCallStack("The last code to use this object was:",
false, requireFullStackTrace);
}
}