    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;
    018
    019import java.io.PrintWriter;
    020import java.time.Duration;
    021import java.time.Instant;
    022import java.util.Deque;
    023
    024/**
    025 * Defines the wrapper that is used to track the additional information, such as
    026 * state, for the pooled objects.
    027 * <p>
    028 * Implementations of this class are required to be thread-safe.
    029 * </p>
    030 *
    031 * @param <T> the type of object in the pool
    032 *
    033 * @since 2.0
    034 */
    035public interface PooledObject<T> extends Comparable<PooledObject<T>> {
    036
    037    /**
    038     * Allocates the object.
    039     *
    040     * @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
    041     */
    042    boolean allocate();
    043
    044    /**
    045     * Orders instances based on idle time - i.e. the length of time since the
    046     * instance was returned to the pool. Used by the GKOP idle object evictor.
    047     *<p>
    048     * Note: This class has a natural ordering that is inconsistent with
    049     *       equals if distinct objects have the same identity hash code.
    050     * </p>
    051     * <p>
    052     * {@inheritDoc}
    053     * </p>
    054     */
    055    @Override
    056    int compareTo(PooledObject<T> other);
    057
    058    /**
    059     * Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
    060     * if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}.
    061     *
    062     * @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}.
    063     */
    064    boolean deallocate();
    065
    066    /**
    067     * Notifies the object that the eviction test has ended.
    068     *
    069     * @param idleQueue The queue of idle objects to which the object should be
    070     *                  returned.
    071     *
    072     * @return  Currently not used.
    073     */
    074    boolean endEvictionTest(Deque<PooledObject<T>> idleQueue);
    075
    076    @Override
    077    boolean equals(Object obj);
    078
    079    /**
    080     * Gets the amount of time this object last spent in the active state (it may still be active in which case
    081     * subsequent calls will return an increased value).
    082     *
    083     * @return The duration last spent in the active state.
    084     * @since 2.11.0
    085     */
    086    default Duration getActiveDuration() {
    087        // Take copies to avoid threading issues
    088        final Instant lastReturnInstant = getLastReturnInstant();
    089        final Instant lastBorrowInstant = getLastBorrowInstant();
    090        // @formatter:off
    091        return lastReturnInstant.isAfter(lastBorrowInstant) ?
    092                Duration.between(lastBorrowInstant, lastReturnInstant) :
    093                Duration.between(lastBorrowInstant, Instant.now());
    094        // @formatter:on
    095    }
    096
    097    /**
    098     * Gets the amount of time this object last spent in the active state (it may still be active in which case
    099     * subsequent calls will return an increased value).
    100     *
    101     * @return The duration last spent in the active state.
    102     * @since 2.10.0
    103     * @deprecated Use {@link #getActiveDuration()}.
    104     */
    105    @Deprecated
    106    default Duration getActiveTime() {
    107        return getActiveDuration();
    108    }
    109
    110    /**
    111     * Gets the amount of time in milliseconds this object last spent in the
    112     * active state (it may still be active in which case subsequent calls will
    113     * return an increased value).
    114     *
    115     * @return The time in milliseconds last spent in the active state.
    116     * @deprecated Use {@link #getActiveTime()} which offers the best precision.
    117     */
    118    @Deprecated
    119    long getActiveTimeMillis();
    120
    121    /**
    122     * Gets the number of times this object has been borrowed.
    123     *
    124     * @return -1 by default for implementations prior to release 2.7.0.
    125     * @since 2.7.0
    126     */
    127    default long getBorrowedCount() {
    128        return -1;
    129    }
    130
    131    /**
    132     * Gets the time (using the same basis as {@link Instant#now()}) that this object was created.
    133     *
    134     * @return The creation time for the wrapped object.
    135     * @since 2.11.0
    136     */
    137    default Instant getCreateInstant() {
    138        return Instant.ofEpochMilli(getCreateTime());
    139    }
    140
    141    /**
    142     * Gets the time (using the same basis as
    143     * {@link System#currentTimeMillis()}) that this object was created.
    144     *
    145     * @return The creation time for the wrapped object.
    146     * @deprecated Use {@link #getCreateInstant()} which offers the best precision.
    147     */
    148    @Deprecated
    149    long getCreateTime();
    150
    151    /**
    152     * Gets the amount of time that this object last spend in the
    153     * idle state (it may still be idle in which case subsequent calls will
    154     * return an increased value).
    155     *
    156     * @return The amount of time in last spent in the idle state.
    157     * @since 2.11.0
    158     */
    159    default Duration getIdleDuration() {
    160        return Duration.ofMillis(getIdleTimeMillis());
    161    }
    162
    163    /**
    164     * Gets the amount of time that this object last spend in the
    165     * idle state (it may still be idle in which case subsequent calls will
    166     * return an increased value).
    167     *
    168     * @return The amount of time in last spent in the idle state.
    169     * @since 2.10.0
    170     * @deprecated Use {@link #getIdleDuration()}.
    171     */
    172    @Deprecated
    173    default Duration getIdleTime() {
    174        return Duration.ofMillis(getIdleTimeMillis());
    175    }
    176
    177    /**
    178     * Gets the amount of time in milliseconds that this object last spend in the
    179     * idle state (it may still be idle in which case subsequent calls will
    180     * return an increased value).
    181     *
    182     * @return The time in milliseconds last spent in the idle state.
    183     * @deprecated Use {@link #getIdleTime()} which offers the best precision.
    184     */
    185    @Deprecated
    186    long getIdleTimeMillis();
    187
    188    /**
    189     * Gets the time the wrapped object was last borrowed.
    190     *
    191     * @return The time the object was last borrowed.
    192     * @since 2.11.0
    193     */
    194    default Instant getLastBorrowInstant() {
    195        return Instant.ofEpochMilli(getLastBorrowTime());
    196    }
    197
    198    /**
    199     * Gets the time the wrapped object was last borrowed.
    200     *
    201     * @return The time the object was last borrowed.
    202     * @deprecated Use {@link #getLastBorrowInstant()} which offers the best precision.
    203     */
    204    @Deprecated
    205    long getLastBorrowTime();
    206
    207    /**
    208     * Gets the time the wrapped object was last borrowed.
    209     *
    210     * @return The time the object was last borrowed.
    211     * @since 2.11.0
    212     */
    213    default Instant getLastReturnInstant() {
    214        return Instant.ofEpochMilli(getLastReturnTime());
    215    }
    216
    217    /**
    218     * Gets the time the wrapped object was last returned.
    219     *
    220     * @return The time the object was last returned.
    221     * @deprecated Use {@link #getLastReturnInstant()} which offers the best precision.
    222     */
    223    @Deprecated
    224    long getLastReturnTime();
    225
    226    /**
    227     * Gets an estimate of the last time this object was used. If the class of the pooled object implements
    228     * {@link TrackedUse}, what is returned is the maximum of {@link TrackedUse#getLastUsedInstant()} and
    229     * {@link #getLastBorrowTime()}; otherwise this method gives the same value as {@link #getLastBorrowTime()}.
    230     *
    231     * @return the last time this object was used
    232     * @since 2.11.0
    233     */
    234    default Instant getLastUsedInstant() {
    235        return Instant.ofEpochMilli(getLastUsedTime());
    236    }
    237
    238    /**
    239     * Gets an estimate of the last time this object was used.  If the class
    240     * of the pooled object implements {@link TrackedUse}, what is returned is
    241     * the maximum of {@link TrackedUse#getLastUsedInstant()} and
    242     * {@link #getLastBorrowTime()}; otherwise this method gives the same
    243     * value as {@link #getLastBorrowTime()}.
    244     *
    245     * @return the last time this object was used.
    246     * @deprecated Use {@link #getLastUsedInstant()} which offers the best precision.
    247     */
    248    @Deprecated
    249    long getLastUsedTime();
    250
    251    /**
    252     * Gets the underlying object that is wrapped by this instance of
    253     * {@link PooledObject}.
    254     *
    255     * @return The wrapped object.
    256     */
    257    T getObject();
    258
    259    /**
    260     * Gets the state of this object.
    261     * @return state
    262     */
    263    PooledObjectState getState();
    264
    265    @Override
    266    int hashCode();
    267
    268    /**
    269     * Sets the state to {@link PooledObjectState#INVALID INVALID}.
    270     */
    271    void invalidate();
    272
    273    /**
    274     * Marks the pooled object as abandoned.
    275     */
    276    void markAbandoned();
    277
    278    /**
    279     * Marks the object as returning to the pool.
    280     */
    281    void markReturning();
    282
    283    /**
    284     * Prints the stack trace of the code that borrowed this pooled object and
    285     * the stack trace of the last code to use this object (if available) to
    286     * the supplied writer.
    287     *
    288     * @param   writer  The destination for the debug output.
    289     */
    290    void printStackTrace(PrintWriter writer);
    291
    292    /**
    293     * Sets whether to use abandoned object tracking. If this is true the
    294     * implementation will need to record the stack trace of the last caller to
    295     * borrow this object.
    296     *
    297     * @param   logAbandoned    The new configuration setting for abandoned
    298     *                          object tracking.
    299     */
    300    void setLogAbandoned(boolean logAbandoned);
    301
    302    /**
    303     * Sets the stack trace generation strategy based on whether or not fully detailed stack traces are required.
    304     * When set to false, abandoned logs may only include caller class information rather than method names, line
    305     * numbers, and other normal metadata available in a full stack trace.
    306     *
    307     * @param requireFullStackTrace the new configuration setting for abandoned object logging.
    308     * @since 2.7.0
    309     */
    310    default void setRequireFullStackTrace(final boolean requireFullStackTrace) {
    311        // noop
    312    }
    313
    314    /**
    315     * Attempts to place the pooled object in the
    316     * {@link PooledObjectState#EVICTION} state.
    317     *
    318     * @return {@code true} if the object was placed in the
    319     *         {@link PooledObjectState#EVICTION} state otherwise
    320     *         {@code false}.
    321     */
    322    boolean startEvictionTest();
    323
    324    /**
    325     * Gets a String form of the wrapper for debug purposes. The format is
    326     * not fixed and may change at any time.
    327     *
    328     * {@inheritDoc}
    329     */
    330    @Override
    331    String toString();
    332
    333    /**
    334     * Records the current stack trace as the last time the object was used.
    335     */
    336    void use();
    337
    338}