001    // Copyright 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.internal.services;
016    
017    import java.lang.reflect.Method;
018    
019    import org.apache.tapestry5.ioc.services.Builtin;
020    import org.apache.tapestry5.ioc.services.PlasticProxyFactory;
021    import org.apache.tapestry5.plastic.ClassInstantiator;
022    import org.apache.tapestry5.plastic.MethodAdvice;
023    import org.apache.tapestry5.plastic.MethodInvocation;
024    import org.apache.tapestry5.plastic.PlasticClass;
025    import org.apache.tapestry5.plastic.PlasticClassTransformer;
026    import org.apache.tapestry5.plastic.PlasticMethod;
027    import org.apache.tapestry5.plastic.PlasticUtils;
028    import org.apache.tapestry5.services.Environment;
029    import org.apache.tapestry5.services.EnvironmentalShadowBuilder;
030    
031    public class EnvironmentalShadowBuilderImpl implements EnvironmentalShadowBuilder
032    {
033        private final PlasticProxyFactory proxyFactory;
034    
035        private final Environment environment;
036    
037        /**
038         * Construct using the default builtin factory, not the component layer version.
039         */
040        public EnvironmentalShadowBuilderImpl(@Builtin
041        PlasticProxyFactory proxyFactory,
042    
043        Environment environment)
044        {
045            this.proxyFactory = proxyFactory;
046            this.environment = environment;
047        }
048    
049        public <T> T build(final Class<T> serviceType)
050        {
051            ClassInstantiator<T> instantiator = proxyFactory.createProxy(serviceType, new PlasticClassTransformer()
052            {
053                public void transform(PlasticClass plasticClass)
054                {
055                    PlasticMethod delegateMethod = plasticClass.introducePrivateMethod(
056                            PlasticUtils.toTypeName(serviceType), "delegate", null, null);
057    
058                    delegateMethod.addAdvice(new MethodAdvice()
059                    {
060                        public void advise(MethodInvocation invocation)
061                        {
062                            invocation.setReturnValue(environment.peekRequired(serviceType));
063                        }
064                    });
065    
066                    for (Method method : serviceType.getMethods())
067                    {
068                        plasticClass.introduceMethod(method).delegateTo(delegateMethod);
069                    }
070    
071                    plasticClass.addToString(String.format("<EnvironmentalProxy for %s>", serviceType.getName()));
072                }
073            });
074    
075            return instantiator.newInstance();
076        }
077    }