    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     * Creates 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     * Gets 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    @Override
    107    public long getBorrowedCount() {
    108        return borrowedCount;
    109    }
    110
    111    /**
    112     * Returns an estimate of the last time this object was used.  If the class
    113     * of the pooled object implements {@link TrackedUse}, what is returned is
    114     * the maximum of {@link TrackedUse#getLastUsed()} and
    115     * {@link #getLastBorrowTime()}; otherwise this method gives the same
    116     * value as {@link #getLastBorrowTime()}.
    117     *
    118     * @return the last time this object was used
    119     */
    120    @Override
    121    public long getLastUsedTime() {
    122        if (object instanceof TrackedUse) {
    123            return Math.max(((TrackedUse) object).getLastUsed(), lastUseTime);
    124        }
    125        return lastUseTime;
    126    }
    127
    128    @Override
    129    public int compareTo(final PooledObject<T> other) {
    130        final long lastActiveDiff = this.getLastReturnTime() - other.getLastReturnTime();
    131        if (lastActiveDiff == 0) {
    132            // Make sure the natural ordering is broadly consistent with equals
    133            // although this will break down if distinct objects have the same
    134            // identity hash code.
    135            // see java.lang.Comparable Javadocs
    136            return System.identityHashCode(this) - System.identityHashCode(other);
    137        }
    138        // handle int overflow
    139        return (int)Math.min(Math.max(lastActiveDiff, Integer.MIN_VALUE), Integer.MAX_VALUE);
    140    }
    141
    142    @Override
    143    public String toString() {
    144        final StringBuilder result = new StringBuilder();
    145        result.append("Object: ");
    146        result.append(object.toString());
    147        result.append(", State: ");
    148        synchronized (this) {
    149            result.append(state.toString());
    150        }
    151        return result.toString();
    152        // TODO add other attributes
    153    }
    154
    155    @Override
    156    public synchronized boolean startEvictionTest() {
    157        if (state == PooledObjectState.IDLE) {
    158            state = PooledObjectState.EVICTION;
    159            return true;
    160        }
    161
    162        return false;
    163    }
    164
    165    @Override
    166    public synchronized boolean endEvictionTest(
    167            final Deque<PooledObject<T>> idleQueue) {
    168        if (state == PooledObjectState.EVICTION) {
    169            state = PooledObjectState.IDLE;
    170            return true;
    171        } else if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
    172            state = PooledObjectState.IDLE;
    173            if (!idleQueue.offerFirst(this)) {
    174                // TODO - Should never happen
    175            }
    176        }
    177
    178        return false;
    179    }
    180
    181    /**
    182     * Allocates the object.
    183     *
    184     * @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
    185     */
    186    @Override
    187    public synchronized boolean allocate() {
    188        if (state == PooledObjectState.IDLE) {
    189            state = PooledObjectState.ALLOCATED;
    190            lastBorrowTime = System.currentTimeMillis();
    191            lastUseTime = lastBorrowTime;
    192            borrowedCount++;
    193            if (logAbandoned) {
    194                borrowedBy.fillInStackTrace();
    195            }
    196            return true;
    197        } else if (state == PooledObjectState.EVICTION) {
    198            // TODO Allocate anyway and ignore eviction test
    199            state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
    200            return false;
    201        }
    202        // TODO if validating and testOnBorrow == true then pre-allocate for
    203        // performance
    204        return false;
    205    }
    206
    207    /**
    208     * Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
    209     * if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}.
    210     *
    211     * @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
    212     */
    213    @Override
    214    public synchronized boolean deallocate() {
    215        if (state == PooledObjectState.ALLOCATED ||
    216                state == PooledObjectState.RETURNING) {
    217            state = PooledObjectState.IDLE;
    218            lastReturnTime = System.currentTimeMillis();
    219            borrowedBy.clear();
    220            return true;
    221        }
    222
    223        return false;
    224    }
    225
    226    /**
    227     * Sets the state to {@link PooledObjectState#INVALID INVALID}
    228     */
    229    @Override
    230    public synchronized void invalidate() {
    231        state = PooledObjectState.INVALID;
    232    }
    233
    234    @Override
    235    public void use() {
    236        lastUseTime = System.currentTimeMillis();
    237        usedBy.fillInStackTrace();
    238    }
    239
    240    @Override
    241    public void printStackTrace(final PrintWriter writer) {
    242        boolean written = borrowedBy.printStackTrace(writer);
    243        written |= usedBy.printStackTrace(writer);
    244        if (written) {
    245            writer.flush();
    246        }
    247    }
    248
    249    /**
    250     * Returns the state of this object.
    251     * @return state
    252     */
    253    @Override
    254    public synchronized PooledObjectState getState() {
    255        return state;
    256    }
    257
    258    /**
    259     * Marks the pooled object as abandoned.
    260     */
    261    @Override
    262    public synchronized void markAbandoned() {
    263        state = PooledObjectState.ABANDONED;
    264    }
    265
    266    /**
    267     * Marks the object as returning to the pool.
    268     */
    269    @Override
    270    public synchronized void markReturning() {
    271        state = PooledObjectState.RETURNING;
    272    }
    273
    274    @Override
    275    public void setLogAbandoned(final boolean logAbandoned) {
    276        this.logAbandoned = logAbandoned;
    277    }
    278
    279    /**
    280     * Configures the stack trace generation strategy based on whether or not fully
    281     * detailed stack traces are required. When set to false, abandoned logs may
    282     * only include caller class information rather than method names, line numbers,
    283     * and other normal metadata available in a full stack trace.
    284     *
    285     * @param requireFullStackTrace the new configuration setting for abandoned object
    286     *                              logging
    287     * @since 2.5
    288     */
    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}