001    // Copyright 2006, 2007, 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.services;
016    
017    import java.util.Map;
018    
019    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
020    import org.apache.tapestry5.ioc.services.Builtin;
021    import org.apache.tapestry5.ioc.services.DefaultImplementationBuilder;
022    import org.apache.tapestry5.ioc.services.PlasticProxyFactory;
023    import org.apache.tapestry5.plastic.ClassInstantiator;
024    import org.apache.tapestry5.plastic.PlasticClass;
025    import org.apache.tapestry5.plastic.PlasticClassTransformer;
026    
027    public class DefaultImplementationBuilderImpl implements DefaultImplementationBuilder
028    {
029        private final Map<Class, Object> cache = CollectionFactory.newConcurrentMap();
030    
031        private final PlasticProxyFactory proxyFactory;
032    
033        public DefaultImplementationBuilderImpl(@Builtin
034        PlasticProxyFactory proxyFactory)
035        {
036            this.proxyFactory = proxyFactory;
037        }
038    
039        public <S> S createDefaultImplementation(Class<S> serviceInterface)
040        {
041            S instance = serviceInterface.cast(cache.get(serviceInterface));
042    
043            if (instance == null)
044            {
045                instance = createInstance(serviceInterface);
046                cache.put(serviceInterface, instance);
047            }
048    
049            return instance;
050        }
051    
052        /**
053         * Creates a class and an instance of that class. Updates the cache and returns the instance.
054         */
055        private <S> S createInstance(final Class<S> serviceInterface)
056        {
057            ClassInstantiator instantiator = proxyFactory.createProxy(serviceInterface, new PlasticClassTransformer()
058            {
059                public void transform(PlasticClass plasticClass)
060                {
061                    plasticClass.addToString(String.format("<NoOp %s>", serviceInterface.getName()));
062                }
063            });
064    
065            return serviceInterface.cast(instantiator.newInstance());
066        }
067    }