001    // Copyright 2006, 2008, 2010 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.services;
016    
017    import org.apache.tapestry5.ioc.ObjectCreator;
018    import org.apache.tapestry5.ioc.services.PerThreadValue;
019    import org.apache.tapestry5.ioc.services.PerthreadManager;
020    
021    /**
022     * Provides per-thread implementations of services.
023     */
024    public class PerThreadServiceCreator implements ObjectCreator
025    {
026        private final PerThreadValue<Object> perThreadValue;
027    
028        private final ObjectCreator delegate;
029    
030        public PerThreadServiceCreator(PerthreadManager perthreadManager, ObjectCreator delegate)
031        {
032            perThreadValue = perthreadManager.createValue();
033    
034            this.delegate = delegate;
035        }
036    
037        /**
038         * For each thread, the first call will use the delegate {@link org.apache.tapestry5.ioc.ObjectCreator} to create
039         * an instance, and later calls will reuse the same per-thread instance. The instance is stored in the
040         * {@link org.apache.tapestry5.ioc.services.PerthreadManager} and will be released at the end of the request.
041         */
042        public Object createObject()
043        {
044            if (perThreadValue.exists())
045                return perThreadValue.get();
046    
047            return perThreadValue.set(delegate.createObject());
048        }
049    }