001// Copyright 2006, 2008, 2009, 2010, 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.transform;
016
017import org.apache.tapestry5.ComponentResources;
018import org.apache.tapestry5.annotations.Mixin;
019import org.apache.tapestry5.internal.InternalComponentResources;
020import org.apache.tapestry5.ioc.internal.util.InternalUtils;
021import org.apache.tapestry5.model.MutableComponentModel;
022import org.apache.tapestry5.plastic.*;
023import org.apache.tapestry5.services.ComponentClassResolver;
024import org.apache.tapestry5.services.transform.ComponentClassTransformWorker2;
025import org.apache.tapestry5.services.transform.TransformationSupport;
026
027/**
028 * Supports the {@link org.apache.tapestry5.annotations.Mixin} annotation, which allows a mixin to
029 * be part of the
030 * implementation of a component. The annotation is applied to a field, which will become read-only,
031 * and contain a
032 * reference to the mixin instance.
033 */
034public class MixinWorker implements ComponentClassTransformWorker2
035{
036    private final ComponentClassResolver resolver;
037
038    public MixinWorker(final ComponentClassResolver resolver)
039    {
040        this.resolver = resolver;
041    }
042
043    public void transform(PlasticClass plasticClass, TransformationSupport support, MutableComponentModel model)
044    {
045        for (PlasticField field : plasticClass.getFieldsWithAnnotation(Mixin.class))
046        {
047            replaceFieldWithMixin(model, field);
048        }
049    }
050
051    private void replaceFieldWithMixin(MutableComponentModel model, PlasticField field)
052    {
053        Mixin annotation = field.getAnnotation(Mixin.class);
054
055        field.claim(annotation);
056
057        String mixinType = annotation.value();
058
059        String[] order = annotation.order();
060
061        String fieldType = field.getTypeName();
062
063        String mixinClassName = InternalUtils.isBlank(mixinType) ? fieldType : resolver
064                .resolveMixinTypeToClassName(mixinType);
065
066        model.addMixinClassName(mixinClassName, order);
067
068        replaceFieldAccessWithMixin(field, mixinClassName);
069    }
070
071    private void replaceFieldAccessWithMixin(PlasticField field, String mixinClassName)
072    {
073        ComputedValue<FieldConduit<Object>> provider = createMixinFieldProvider(field.getName(), mixinClassName);
074
075        field.setComputedConduit(provider);
076    }
077
078    private ComputedValue<FieldConduit<Object>> createMixinFieldProvider(final String fieldName,
079            final String mixinClassName)
080    {
081        return new ComputedValue<FieldConduit<Object>>()
082        {
083            public FieldConduit get(InstanceContext context)
084            {
085                ComponentResources resources = context.get(ComponentResources.class);
086                final InternalComponentResources icr = (InternalComponentResources) resources;
087
088                return new ReadOnlyComponentFieldConduit(resources, fieldName)
089                {
090                    public Object get(Object instance, InstanceContext context)
091                    {
092                        return icr.getMixinByClassName(mixinClassName);
093                    }
094                };
095            }
096        };
097    }
098}