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
015package org.apache.tapestry5.ioc.internal.util;
016
017import java.util.concurrent.locks.Lock;
018import 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 */
024public 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     * @deprecated Deprecated in 5.4 with no replacement.
043     */
044    public static Lock createLockForThreadLocalCreation()
045    {
046        return JDK_1_5 ? new ReentrantLock() : new DummyLock();
047    }
048}