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;
020
021import org.apache.commons.pool2.PooledObject;
022import org.apache.commons.pool2.UsageTracking;
023
024/**
025 * Strategy for obtaining and printing the current call stack. This is primarily useful for
026 * {@linkplain UsageTracking usage tracking} so that different JVMs and configurations can use more efficient strategies
027 * for obtaining the current call stack depending on metadata needs.
028 *
029 * @see CallStackUtils
030 * @since 2.4.3
031 */
032public interface CallStack {
033
034    /**
035     * Clears the current stack trace snapshot. Subsequent calls to {@link #printStackTrace(PrintWriter)} will be
036     * no-ops until another call to {@link #fillInStackTrace()}.
037     */
038    void clear();
039
040    /**
041     * Takes a snapshot of the current call stack. Subsequent calls to {@link #printStackTrace(PrintWriter)} will print
042     * out that stack trace until it is {@linkplain #clear() cleared}.
043     */
044    void fillInStackTrace();
045
046    /**
047     * Prints the current stack trace if available to a PrintWriter. The format is undefined and is primarily useful
048     * for debugging issues with {@link PooledObject} usage in user code.
049     *
050     * @param writer a PrintWriter to write the current stack trace to if available
051     * @return true if a stack trace was available to print or false if nothing was printed
052     */
053    boolean printStackTrace(final PrintWriter writer);
054}