    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(new PrivilegedAction<PrivateSecurityManager>() {
    056            @Override
    057            public PrivateSecurityManager run() {
    058                return new PrivateSecurityManager();
    059            }
    060        });
    061    }
    062
    063    @Override
    064    public boolean printStackTrace(final PrintWriter writer) {
    065        final Snapshot snapshotRef = this.snapshot;
    066        if (snapshotRef == null) {
    067            return false;
    068        }
    069        final String message;
    070        if (dateFormat == null) {
    071            message = messageFormat;
    072        } else {
    073            synchronized (dateFormat) {
    074                message = dateFormat.format(Long.valueOf(snapshotRef.timestamp));
    075            }
    076        }
    077        writer.println(message);
    078        for (final WeakReference<Class<?>> reference : snapshotRef.stack) {
    079            writer.println(reference.get());
    080        }
    081        return true;
    082    }
    083
    084    @Override
    085    public void fillInStackTrace() {
    086        snapshot = new Snapshot(securityManager.getCallStack());
    087    }
    088
    089    @Override
    090    public void clear() {
    091        snapshot = null;
    092    }
    093
    094    /**
    095     * A custom security manager.
    096     */
    097    private static class PrivateSecurityManager extends SecurityManager {
    098        /**
    099         * Get the class stack.
    100         *
    101         * @return class stack
    102         */
    103        private List<WeakReference<Class<?>>> getCallStack() {
    104            final Class<?>[] classes = getClassContext();
    105            final List<WeakReference<Class<?>>> stack = new ArrayList<>(classes.length);
    106            for (final Class<?> klass : classes) {
    107                stack.add(new WeakReference<Class<?>>(klass));
    108            }
    109            return stack;
    110        }
    111    }
    112
    113    /**
    114     * A snapshot of a class stack.
    115     */
    116    private static class Snapshot {
    117        private final long timestamp = System.currentTimeMillis();
    118        private final List<WeakReference<Class<?>>> stack;
    119
    120        /**
    121         * Create a new snapshot with a class stack.
    122         *
    123         * @param stack class stack
    124         */
    125        private Snapshot(final List<WeakReference<Class<?>>> stack) {
    126            this.stack = stack;
    127        }
    128    }
    129}