    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}