    001    // Copyright 2009, 2011 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.ioc.internal.util;
    016
    017    import java.util.concurrent.locks.Lock;
    018    import java.util.concurrent.locks.ReentrantLock;
    019
    020    /**
    021     * Internal utilities for identifying the JDK version, used in the rare cases
    022     * that we are patching around JDK bugs.
    023     */
    024    public class JDKUtils
    025    {
    026        /**
    027         * Is the running JVM JDK 1.5?
    028         */
    029        public static final boolean JDK_1_5 = isVersion("1.5");
    030
    031        private static boolean isVersion(String versionId)
    032        {
    033            return System.getProperty("java.specification.version").equals(versionId);
    034        }
    035
    036        /**
    037         * Returns a {@link ReentrantLock} used to serialize access to the construction of a thread local; this is only needed under JDK 1.5 (due to a bug in the JDK);
    038         * for other JDKs, a {@link DummyLock} is returned.
    039         *
    040         * @return lock to use when creating
    041         * @since 5.3
    042         */
    043        public static Lock createLockForThreadLocalCreation()
    044        {
    045            return JDK_1_5 ? new ReentrantLock() : new DummyLock();
    046        }
    047    }