    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
    015    package org.apache.tapestry5.internal.transform;
    016
    017    import org.apache.tapestry5.ComponentResources;
    018    import org.apache.tapestry5.annotations.Mixin;
    019    import org.apache.tapestry5.internal.InternalComponentResources;
    020    import org.apache.tapestry5.ioc.internal.util.InternalUtils;
    021    import org.apache.tapestry5.model.MutableComponentModel;
    022    import org.apache.tapestry5.plastic.*;
    023    import org.apache.tapestry5.services.ComponentClassResolver;
    024    import org.apache.tapestry5.services.transform.ComponentClassTransformWorker2;
    025    import 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     */
    034    public 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    }