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
015package org.apache.tapestry5.internal.services;
016
017import java.lang.reflect.Method;
018
019import org.apache.tapestry5.commons.services.PlasticProxyFactory;
020import org.apache.tapestry5.ioc.services.Builtin;
021import org.apache.tapestry5.plastic.ClassInstantiator;
022import org.apache.tapestry5.plastic.MethodAdvice;
023import org.apache.tapestry5.plastic.MethodInvocation;
024import org.apache.tapestry5.plastic.PlasticClass;
025import org.apache.tapestry5.plastic.PlasticClassTransformer;
026import org.apache.tapestry5.plastic.PlasticMethod;
027import org.apache.tapestry5.plastic.PlasticUtils;
028import org.apache.tapestry5.services.Environment;
029import org.apache.tapestry5.services.EnvironmentalShadowBuilder;
030
031public 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}