    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    /**
    034     * A snapshot of a throwable.
    035     */
    036    private static class Snapshot extends Throwable {
    037        private static final long serialVersionUID = 1L;
    038        private final long timestampMillis = System.currentTimeMillis();
    039    }
    040
    041    private final String messageFormat;
    042
    043    //@GuardedBy("dateFormat")
    044    private final DateFormat dateFormat;
    045
    046    private volatile Snapshot snapshot;
    047
    048    /**
    049     * Creates a new instance.
    050     *
    051     * @param messageFormat message format
    052     * @param useTimestamp whether to format the dates in the output message or not
    053     */
    054    public ThrowableCallStack(final String messageFormat, final boolean useTimestamp) {
    055        this.messageFormat = messageFormat;
    056        this.dateFormat = useTimestamp ? new SimpleDateFormat(messageFormat) : null;
    057    }
    058
    059    @Override
    060    public void clear() {
    061        snapshot = null;
    062    }
    063
    064    @Override
    065    public void fillInStackTrace() {
    066        snapshot = new Snapshot();
    067    }
    068
    069    @Override
    070    public synchronized boolean printStackTrace(final PrintWriter writer) {
    071        final Snapshot snapshotRef = this.snapshot;
    072        if (snapshotRef == null) {
    073            return false;
    074        }
    075        final String message;
    076        if (dateFormat == null) {
    077            message = messageFormat;
    078        } else {
    079            synchronized (dateFormat) {
    080                message = dateFormat.format(Long.valueOf(snapshotRef.timestampMillis));
    081            }
    082        }
    083        writer.println(message);
    084        snapshotRef.printStackTrace(writer);
    085        return true;
    086    }
    087}