001    // Copyright 2006, 2007 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.internal.services;
016    
017    import org.apache.tapestry5.ioc.AnnotationProvider;
018    import org.apache.tapestry5.ioc.ObjectLocator;
019    import org.apache.tapestry5.ioc.ObjectProvider;
020    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
021    import org.apache.tapestry5.services.Alias;
022    import org.apache.tapestry5.services.AliasManager;
023    
024    import java.util.Map;
025    
026    public class AliasImpl implements Alias, ObjectProvider
027    {
028        // Derived from the managers when first needed
029    
030        private final Map<Class, Object> properties = CollectionFactory.newMap();
031    
032        private final String mode;
033    
034        private boolean initialized = false;
035    
036        private AliasManager masterManager;
037    
038        private AliasManager overridesManager;
039    
040        public AliasImpl(AliasManager masterManager, String mode, AliasManager overridesManager)
041        {
042            this.masterManager = masterManager;
043            this.mode = mode;
044            this.overridesManager = overridesManager;
045        }
046    
047        public ObjectProvider getObjectProvider()
048        {
049            return this;
050        }
051    
052        private synchronized void initialize()
053        {
054            if (initialized) return;
055    
056            properties.putAll(masterManager.getAliasesForMode(mode));
057            properties.putAll(overridesManager.getAliasesForMode(mode));
058    
059            masterManager = null;
060            overridesManager = null;
061    
062            initialized = true;
063        }
064    
065        public <T> T provide(Class<T> objectType, AnnotationProvider annotationProvider,
066                             ObjectLocator locator)
067        {
068            initialize();
069    
070            Object object = properties.get(objectType);
071    
072            // Let another provider handle this (probably the default object provider)
073            if (object == null) return null;
074    
075            // A ClassCastException should never occur.
076    
077            return objectType.cast(object);
078        }
079    }