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;
022
023/**
024 * CallStack strategy that uses the stack trace from a {@link Throwable}. This strategy, while slower than the
025 * SecurityManager implementation, provides call stack method names and other metadata in addition to the call stack
026 * of classes.
027 *
028 * @see Throwable#fillInStackTrace()
029 * @since 2.4.3
030 */
031public class ThrowableCallStack implements CallStack {
032
033    private final String messageFormat;
034    //@GuardedBy("dateFormat")
035    private final DateFormat dateFormat;
036
037    private volatile Snapshot snapshot;
038
039    /**
040     * Create a new instance.
041     *
042     * @param messageFormat message format
043     * @param useTimestamp whether to format the dates in the output message or not
044     */
045    public ThrowableCallStack(final String messageFormat, final boolean useTimestamp) {
046        this.messageFormat = messageFormat;
047        this.dateFormat = useTimestamp ? new SimpleDateFormat(messageFormat) : null;
048    }
049
050    @Override
051    public synchronized boolean printStackTrace(final PrintWriter writer) {
052        final Snapshot snapshotRef = this.snapshot;
053        if (snapshotRef == null) {
054            return false;
055        }
056        final String message;
057        if (dateFormat == null) {
058            message = messageFormat;
059        } else {
060            synchronized (dateFormat) {
061                message = dateFormat.format(Long.valueOf(snapshotRef.timestamp));
062            }
063        }
064        writer.println(message);
065        snapshotRef.printStackTrace(writer);
066        return true;
067    }
068
069    @Override
070    public void fillInStackTrace() {
071        snapshot = new Snapshot();
072    }
073
074    @Override
075    public void clear() {
076        snapshot = null;
077    }
078
079    /**
080     * A snapshot of a throwable.
081     */
082    private static class Snapshot extends Throwable {
083        private static final long serialVersionUID = 1L;
084        private final long timestamp = System.currentTimeMillis();
085    }
086}