    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.pool2.impl;
    018
    019import org.apache.commons.pool2.PooledObject;
    020import org.apache.commons.pool2.PooledObjectState;
    021import org.apache.commons.pool2.TrackedUse;
    022
    023import java.io.PrintWriter;
    024import java.util.Deque;
    025
    026/**
    027 * This wrapper is used to track the additional information, such as state, for
    028 * the pooled objects.
    029 * <p>
    030 * This class is intended to be thread-safe.
    031 * </p>
    032 *
    033 * @param <T> the type of object in the pool
    034 *
    035 * @since 2.0
    036 */
    037public class DefaultPooledObject<T> implements PooledObject<T> {
    038
    039    private final T object;
    040    private PooledObjectState state = PooledObjectState.IDLE; // @GuardedBy("this") to ensure transitions are valid
    041    private final long createTime = System.currentTimeMillis();
    042    private volatile long lastBorrowTime = createTime;
    043    private volatile long lastUseTime = createTime;
    044    private volatile long lastReturnTime = createTime;
    045    private volatile boolean logAbandoned = false;
    046    private volatile CallStack borrowedBy = NoOpCallStack.INSTANCE;
    047    private volatile CallStack usedBy = NoOpCallStack.INSTANCE;
    048    private volatile long borrowedCount = 0;
    049
    050    /**
    051     * Create a new instance that wraps the provided object so that the pool can
    052     * track the state of the pooled object.
    053     *
    054     * @param object The object to wrap
    055     */
    056    public DefaultPooledObject(final T object) {
    057        this.object = object;
    058    }
    059
    060    @Override
    061    public T getObject() {
    062        return object;
    063    }
    064
    065    @Override
    066    public long getCreateTime() {
    067        return createTime;
    068    }
    069
    070    @Override
    071    public long getActiveTimeMillis() {
    072        // Take copies to avoid threading issues
    073        final long rTime = lastReturnTime;
    074        final long bTime = lastBorrowTime;
    075
    076        if (rTime > bTime) {
    077            return rTime - bTime;
    078        }
    079        return System.currentTimeMillis() - bTime;
    080    }
    081
    082    @Override
    083    public long getIdleTimeMillis() {
    084        final long elapsed = System.currentTimeMillis() - lastReturnTime;
    085        // elapsed may be negative if:
    086        // - another thread updates lastReturnTime during the calculation window
    087        // - System.currentTimeMillis() is not monotonic (e.g. system time is set back)
    088        return elapsed >= 0 ? elapsed : 0;
    089    }
    090
    091    @Override
    092    public long getLastBorrowTime() {
    093        return lastBorrowTime;
    094    }
    095
    096    @Override
    097    public long getLastReturnTime() {
    098        return lastReturnTime;
    099    }
    100
    101    /**
    102     * Get the number of times this object has been borrowed.
    103     * @return The number of times this object has been borrowed.
    104     * @since 2.1
    105     */
    106    public long getBorrowedCount() {
    107        return borrowedCount;
    108    }
    109
    110    /**
    111     * Return an estimate of the last time this object was used.  If the class
    112     * of the pooled object implements {@link TrackedUse}, what is returned is
    113     * the maximum of {@link TrackedUse#getLastUsed()} and
    114     * {@link #getLastBorrowTime()}; otherwise this method gives the same
    115     * value as {@link #getLastBorrowTime()}.
    116     *
    117     * @return the last time this object was used
    118     */
    119    @Override
    120    public long getLastUsedTime() {
    121        if (object instanceof TrackedUse) {
    122            return Math.max(((TrackedUse) object).getLastUsed(), lastUseTime);
    123        }
    124        return lastUseTime;
    125    }
    126
    127    @Override
    128    public int compareTo(final PooledObject<T> other) {
    129        final long lastActiveDiff = this.getLastReturnTime() - other.getLastReturnTime();
    130        if (lastActiveDiff == 0) {
    131            // Make sure the natural ordering is broadly consistent with equals
    132            // although this will break down if distinct objects have the same
    133            // identity hash code.
    134            // see java.lang.Comparable Javadocs
    135            return System.identityHashCode(this) - System.identityHashCode(other);
    136        }
    137        // handle int overflow
    138        return (int)Math.min(Math.max(lastActiveDiff, Integer.MIN_VALUE), Integer.MAX_VALUE);
    139    }
    140
    141    @Override
    142    public String toString() {
    143        final StringBuilder result = new StringBuilder();
    144        result.append("Object: ");
    145        result.append(object.toString());
    146        result.append(", State: ");
    147        synchronized (this) {
    148            result.append(state.toString());
    149        }
    150        return result.toString();
    151        // TODO add other attributes
    152    }
    153
    154    @Override
    155    public synchronized boolean startEvictionTest() {
    156        if (state == PooledObjectState.IDLE) {
    157            state = PooledObjectState.EVICTION;
    158            return true;
    159        }
    160
    161        return false;
    162    }
    163
    164    @Override
    165    public synchronized boolean endEvictionTest(
    166            final Deque<PooledObject<T>> idleQueue) {
    167        if (state == PooledObjectState.EVICTION) {
    168            state = PooledObjectState.IDLE;
    169            return true;
    170        } else if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
    171            state = PooledObjectState.IDLE;
    172            if (!idleQueue.offerFirst(this)) {
    173                // TODO - Should never happen
    174            }
    175        }
    176
    177        return false;
    178    }
    179
    180    /**
    181     * Allocates the object.
    182     *
    183     * @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
    184     */
    185    @Override
    186    public synchronized boolean allocate() {
    187        if (state == PooledObjectState.IDLE) {
    188            state = PooledObjectState.ALLOCATED;
    189            lastBorrowTime = System.currentTimeMillis();
    190            lastUseTime = lastBorrowTime;
    191            borrowedCount++;
    192            if (logAbandoned) {
    193                borrowedBy.fillInStackTrace();
    194            }
    195            return true;
    196        } else if (state == PooledObjectState.EVICTION) {
    197            // TODO Allocate anyway and ignore eviction test
    198            state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
    199            return false;
    200        }
    201        // TODO if validating and testOnBorrow == true then pre-allocate for
    202        // performance
    203        return false;
    204    }
    205
    206    /**
    207     * Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
    208     * if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}.
    209     *
    210     * @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
    211     */
    212    @Override
    213    public synchronized boolean deallocate() {
    214        if (state == PooledObjectState.ALLOCATED ||
    215                state == PooledObjectState.RETURNING) {
    216            state = PooledObjectState.IDLE;
    217            lastReturnTime = System.currentTimeMillis();
    218            borrowedBy.clear();
    219            return true;
    220        }
    221
    222        return false;
    223    }
    224
    225    /**
    226     * Sets the state to {@link PooledObjectState#INVALID INVALID}
    227     */
    228    @Override
    229    public synchronized void invalidate() {
    230        state = PooledObjectState.INVALID;
    231    }
    232
    233    @Override
    234    public void use() {
    235        lastUseTime = System.currentTimeMillis();
    236        usedBy.fillInStackTrace();
    237    }
    238
    239    @Override
    240    public void printStackTrace(final PrintWriter writer) {
    241        boolean written = borrowedBy.printStackTrace(writer);
    242        written |= usedBy.printStackTrace(writer);
    243        if (written) {
    244            writer.flush();
    245        }
    246    }
    247
    248    /**
    249     * Returns the state of this object.
    250     * @return state
    251     */
    252    @Override
    253    public synchronized PooledObjectState getState() {
    254        return state;
    255    }
    256
    257    /**
    258     * Marks the pooled object as abandoned.
    259     */
    260    @Override
    261    public synchronized void markAbandoned() {
    262        state = PooledObjectState.ABANDONED;
    263    }
    264
    265    /**
    266     * Marks the object as returning to the pool.
    267     */
    268    @Override
    269    public synchronized void markReturning() {
    270        state = PooledObjectState.RETURNING;
    271    }
    272
    273    @Override
    274    public void setLogAbandoned(final boolean logAbandoned) {
    275        this.logAbandoned = logAbandoned;
    276    }
    277
    278    /**
    279     * Configures the stack trace generation strategy based on whether or not fully
    280     * detailed stack traces are required. When set to false, abandoned logs may
    281     * only include caller class information rather than method names, line numbers,
    282     * and other normal metadata available in a full stack trace.
    283     *
    284     * @param requireFullStackTrace the new configuration setting for abandoned object
    285     *                              logging
    286     * @since 2.5
    287     */
    288    // TODO: uncomment below in 3.0
    289    // @Override
    290    public void setRequireFullStackTrace(final boolean requireFullStackTrace) {
    291        borrowedBy = CallStackUtils.newCallStack("'Pooled object created' " +
    292            "yyyy-MM-dd HH:mm:ss Z 'by the following code has not been returned to the pool:'",
    293            true, requireFullStackTrace);
    294        usedBy = CallStackUtils.newCallStack("The last code to use this object was:",
    295            false, requireFullStackTrace);
    296    }
    297
    298}