001    // Copyright 2005 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.hivemind.internal.ser;
016    
017    import java.lang.ref.WeakReference;
018    
019    import org.apache.hivemind.ApplicationRuntimeException;
020    
021    /**
022     * Class used to hold a <em>global</em> instance of
023     * {@link org.apache.hivemind.internal.ser.ServiceSerializationSupport}, so that
024     * {@link org.apache.hivemind.internal.ser.ServiceToken}s may locate them.
025     * 
026     * @author Howard M. Lewis Ship
027     * @since 1.1
028     */
029    public class ServiceSerializationHelper
030    {
031        private static final ThreadLocal _threadLocal = new ThreadLocal();
032    
033        /**
034         * Returns the previously stored SSS.
035         * 
036         * @throws ApplicationRuntimeException
037         *             if no SSS has been stored.
038         */
039        public static ServiceSerializationSupport getServiceSerializationSupport()
040        {
041            ServiceSerializationSupport result = null;
042    
043            WeakReference reference = (WeakReference) _threadLocal.get();
044            if (reference != null)
045                result = (ServiceSerializationSupport) reference.get();
046    
047            if (result == null)
048                throw new ApplicationRuntimeException(SerMessages.noSupportSet());
049    
050            return result;
051        }
052    
053        /**
054         * Stores the SSS instance for later access; if an existing SSS is already stored, then an error
055         * is logged (should be just one SSS per class loader).
056         */
057    
058        public static void setServiceSerializationSupport(
059                ServiceSerializationSupport serviceSerializationSupport)
060        {
061            WeakReference reference = new WeakReference(serviceSerializationSupport);
062    
063            _threadLocal.set(reference);
064        }
065    }