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 java.io.PrintWriter;
020import java.text.DateFormat;
021import java.text.SimpleDateFormat;
022import java.time.Instant;
023
024/**
025 * CallStack strategy that uses the stack trace from a {@link Throwable}. This strategy, while slower than the
026 * SecurityManager implementation, provides call stack method names and other metadata in addition to the call stack
027 * of classes.
028 *
029 * @see Throwable#fillInStackTrace()
030 * @since 2.4.3
031 */
032public class ThrowableCallStack implements CallStack {
033
034    /**
035     * A snapshot of a throwable.
036     */
037    private static final class Snapshot extends Throwable {
038
039        private static final long serialVersionUID = 1L;
040        private final Instant timestamp;
041
042        /**
043         * Constructs a new instance with its message set to the now instant.
044         */
045        public Snapshot() {
046            this(Instant.now());
047        }
048
049        /**
050         * Constructs a new instance and use the timestamp as the message with using {@link DateTimeFormatter#ISO_INSTANT} for more precision.
051         *
052         * @param timestamp normally the now instant.
053         */
054        private Snapshot(final Instant timestamp) {
055            super(timestamp.toString());
056            this.timestamp = timestamp;
057        }
058    }
059
060    private final String messageFormat;
061
062    // We keep the SimpleDateFormat for backward compatibility instead of a DateTimeFormatter.
063    //@GuardedBy("dateFormat")
064    private final DateFormat dateFormat;
065
066    private volatile Snapshot snapshot;
067
068    /**
069     * Creates a new instance.
070     *
071     * @param messageFormat message format
072     * @param useTimestamp whether to format the dates in the output message or not
073     */
074    public ThrowableCallStack(final String messageFormat, final boolean useTimestamp) {
075        this.messageFormat = messageFormat;
076        this.dateFormat = useTimestamp ? new SimpleDateFormat(messageFormat) : null;
077    }
078
079    @Override
080    public void clear() {
081        snapshot = null;
082    }
083
084    @Override
085    public void fillInStackTrace() {
086        snapshot = new Snapshot();
087    }
088
089    @Override
090    public synchronized boolean printStackTrace(final PrintWriter writer) {
091        final Snapshot snapshotRef = this.snapshot;
092        if (snapshotRef == null) {
093            return false;
094        }
095        final String message;
096        if (dateFormat == null) {
097            message = messageFormat;
098        } else {
099            synchronized (dateFormat) {
100                // The throwable message is in {@link DateTimeFormatter#ISO_INSTANT} format for more precision.
101                message = dateFormat.format(Long.valueOf(snapshotRef.timestamp.toEpochMilli()));
102            }
103        }
104        writer.println(message);
105        snapshotRef.printStackTrace(writer);
106        return true;
107    }
108}