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.lang.ref.WeakReference;
021import java.security.AccessController;
022import java.security.PrivilegedAction;
023import java.text.DateFormat;
024import java.text.SimpleDateFormat;
025import java.util.ArrayList;
026import java.util.List;
027
028/**
029 * CallStack strategy using a {@link SecurityManager}. Obtaining the current call stack is much faster via a
030 * SecurityManger, but access to the underlying method may be restricted by the current SecurityManager. In environments
031 * where a SecurityManager cannot be created, {@link ThrowableCallStack} should be used instead.
032 *
033 * @see RuntimePermission
034 * @see SecurityManager#getClassContext()
035 * @since 2.4.3
036 */
037public class SecurityManagerCallStack implements CallStack {
038
039    private final String messageFormat;
040    //@GuardedBy("dateFormat")
041    private final DateFormat dateFormat;
042    private final PrivateSecurityManager securityManager;
043
044    private volatile Snapshot snapshot;
045
046    /**
047     * Create a new instance.
048     *
049     * @param messageFormat message format
050     * @param useTimestamp whether to format the dates in the output message or not
051     */
052    public SecurityManagerCallStack(final String messageFormat, final boolean useTimestamp) {
053        this.messageFormat = messageFormat;
054        this.dateFormat = useTimestamp ? new SimpleDateFormat(messageFormat) : null;
055        this.securityManager = AccessController.doPrivileged((PrivilegedAction<PrivateSecurityManager>) () -> new PrivateSecurityManager());
056    }
057
058    @Override
059    public boolean printStackTrace(final PrintWriter writer) {
060        final Snapshot snapshotRef = this.snapshot;
061        if (snapshotRef == null) {
062            return false;
063        }
064        final String message;
065        if (dateFormat == null) {
066            message = messageFormat;
067        } else {
068            synchronized (dateFormat) {
069                message = dateFormat.format(Long.valueOf(snapshotRef.timestamp));
070            }
071        }
072        writer.println(message);
073        for (final WeakReference<Class<?>> reference : snapshotRef.stack) {
074            writer.println(reference.get());
075        }
076        return true;
077    }
078
079    @Override
080    public void fillInStackTrace() {
081        snapshot = new Snapshot(securityManager.getCallStack());
082    }
083
084    @Override
085    public void clear() {
086        snapshot = null;
087    }
088
089    /**
090     * A custom security manager.
091     */
092    private static class PrivateSecurityManager extends SecurityManager {
093        /**
094         * Get the class stack.
095         *
096         * @return class stack
097         */
098        private List<WeakReference<Class<?>>> getCallStack() {
099            final Class<?>[] classes = getClassContext();
100            final List<WeakReference<Class<?>>> stack = new ArrayList<>(classes.length);
101            for (final Class<?> klass : classes) {
102                stack.add(new WeakReference<Class<?>>(klass));
103            }
104            return stack;
105        }
106    }
107
108    /**
109     * A snapshot of a class stack.
110     */
111    private static class Snapshot {
112        private final long timestamp = System.currentTimeMillis();
113        private final List<WeakReference<Class<?>>> stack;
114
115        /**
116         * Create a new snapshot with a class stack.
117         *
118         * @param stack class stack
119         */
120        private Snapshot(final List<WeakReference<Class<?>>> stack) {
121            this.stack = stack;
122        }
123    }
124}