    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.dbcp2;
    018
    019import java.lang.ref.WeakReference;
    020import java.util.ArrayList;
    021import java.util.Collections;
    022import java.util.Iterator;
    023import java.util.List;
    024
    025import org.apache.commons.pool2.TrackedUse;
    026
    027/**
    028 * Tracks db connection usage for recovering and reporting abandoned db connections.
    029 * <p>
    030 * The JDBC Connection, Statement, and ResultSet classes extend this class.
    031 * </p>
    032 *
    033 * @since 2.0
    034 */
    035public class AbandonedTrace implements TrackedUse {
    036
    037    /** A list of objects created by children of this object. */
    038    private final List<WeakReference<AbandonedTrace>> traceList = new ArrayList<>();
    039
    040    /** Last time this connection was used. */
    041    private volatile long lastUsedMillis = 0;
    042
    043    /**
    044     * Creates a new AbandonedTrace without config and without doing abandoned tracing.
    045     */
    046    public AbandonedTrace() {
    047        init(null);
    048    }
    049
    050    /**
    051     * Constructs a new AbandonedTrace with a parent object.
    052     *
    053     * @param parent
    054     *            AbandonedTrace parent object.
    055     */
    056    public AbandonedTrace(final AbandonedTrace parent) {
    057        init(parent);
    058    }
    059
    060    /**
    061     * Adds an object to the list of objects being traced.
    062     *
    063     * @param trace
    064     *            AbandonedTrace object to add.
    065     */
    066    protected void addTrace(final AbandonedTrace trace) {
    067        synchronized (this.traceList) {
    068            this.traceList.add(new WeakReference<>(trace));
    069        }
    070        setLastUsed();
    071    }
    072
    073    /**
    074     * Clears the list of objects being traced by this object.
    075     */
    076    protected void clearTrace() {
    077        synchronized (this.traceList) {
    078            this.traceList.clear();
    079        }
    080    }
    081
    082    /**
    083     * Gets the last time this object was used in milliseconds.
    084     *
    085     * @return long time in milliseconds.
    086     */
    087    @Override
    088    public long getLastUsed() {
    089        return lastUsedMillis;
    090    }
    091
    092    /**
    093     * Gets a list of objects being traced by this object.
    094     *
    095     * @return List of objects.
    096     */
    097    protected List<AbandonedTrace> getTrace() {
    098        final int size = traceList.size();
    099        if (size == 0) {
    100            return Collections.emptyList();
    101        }
    102        final ArrayList<AbandonedTrace> result = new ArrayList<>(size);
    103        synchronized (this.traceList) {
    104            final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
    105            while (iter.hasNext()) {
    106                final AbandonedTrace trace = iter.next().get();
    107                if (trace == null) {
    108                    // Clean-up since we are here anyway
    109                    iter.remove();
    110                } else {
    111                    result.add(trace);
    112                }
    113            }
    114        }
    115        return result;
    116    }
    117
    118    /**
    119     * Initializes abandoned tracing for this object.
    120     *
    121     * @param parent
    122     *            AbandonedTrace parent object.
    123     */
    124    private void init(final AbandonedTrace parent) {
    125        if (parent != null) {
    126            parent.addTrace(this);
    127        }
    128    }
    129
    130    /**
    131     * Removes this object the source object is tracing.
    132     *
    133     * @param source The object tracing
    134     * @since 2.7.0
    135     */
    136    protected void removeThisTrace(final Object source) {
    137        if (source instanceof AbandonedTrace) {
    138            AbandonedTrace.class.cast(source).removeTrace(this);
    139        }
    140    }
    141
    142    /**
    143     * Removes a child object this object is tracing.
    144     *
    145     * @param trace
    146     *            AbandonedTrace object to remove.
    147     */
    148    protected void removeTrace(final AbandonedTrace trace) {
    149        synchronized (this.traceList) {
    150            final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
    151            while (iter.hasNext()) {
    152                final AbandonedTrace traceInList = iter.next().get();
    153                if (trace != null && trace.equals(traceInList)) {
    154                    iter.remove();
    155                    break;
    156                } else if (traceInList == null) {
    157                    // Clean-up since we are here anyway
    158                    iter.remove();
    159                }
    160            }
    161        }
    162    }
    163
    164    /**
    165     * Sets the time this object was last used to the current time in milliseconds.
    166     */
    167    protected void setLastUsed() {
    168        lastUsedMillis = System.currentTimeMillis();
    169    }
    170
    171    /**
    172     * Sets the time in milliseconds this object was last used.
    173     *
    174     * @param lastUsedMillis
    175     *            time in milliseconds.
    176     */
    177    protected void setLastUsed(final long lastUsedMillis) {
    178        this.lastUsedMillis = lastUsedMillis;
    179    }
    180}