001// Copyright 2006, 2007, 2008, 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.annotations.Environmental;
018import org.apache.tapestry5.internal.services.ComponentClassCache;
019import org.apache.tapestry5.model.MutableComponentModel;
020import org.apache.tapestry5.plastic.*;
021import org.apache.tapestry5.services.Environment;
022import org.apache.tapestry5.services.transform.ComponentClassTransformWorker2;
023import org.apache.tapestry5.services.transform.TransformationSupport;
024
025/**
026 * Obtains a value from the {@link Environment} service based on the field type. This is triggered by the presence of
027 * the {@link Environmental} annotation.
028 */
029@SuppressWarnings("rawtypes")
030public class EnvironmentalWorker implements ComponentClassTransformWorker2
031{
032    private final Environment environment;
033
034    private final ComponentClassCache classCache;
035
036
037    @SuppressWarnings("unchecked")
038    private final class EnvironmentalConduit implements FieldConduit
039    {
040        private final String componentClassName;
041
042        private final String fieldName;
043
044        private final Class environmentalType;
045
046        private final boolean required;
047
048        private EnvironmentalConduit(String componentClassName, String fieldName, final Class environmentalType,
049                boolean required)
050        {
051            this.componentClassName = componentClassName;
052            this.fieldName = fieldName;
053            this.environmentalType = environmentalType;
054            this.required = required;
055        }
056
057        public Object get(Object instance, InstanceContext context)
058        {
059            return required ? environment.peekRequired(environmentalType) : environment.peek(environmentalType);
060        }
061
062        public void set(Object instance, InstanceContext context, Object newValue)
063        {
064            throw new RuntimeException(String.format("Field %s.%s is read only.", componentClassName, fieldName));
065        }
066    }
067
068    public EnvironmentalWorker(Environment environment, ComponentClassCache classCache)
069    {
070        this.environment = environment;
071
072        this.classCache = classCache;
073    }
074
075    public void transform(PlasticClass plasticClass, TransformationSupport support, MutableComponentModel model)
076    {
077        for (PlasticField field : plasticClass.getFieldsWithAnnotation(Environmental.class))
078        {
079            transform(model.getComponentClassName(), field);
080        }
081    }
082
083    private void transform(final String componentClassName, PlasticField field)
084    {
085        Environmental annotation = field.getAnnotation(Environmental.class);
086
087        field.claim(annotation);
088
089        final String fieldName = field.getName();
090
091        final Class fieldType = classCache.forName(field.getTypeName());
092
093        final boolean required = annotation.value();
094
095        ComputedValue<FieldConduit<Object>> provider = new ComputedValue<FieldConduit<Object>>()
096        {
097            public FieldConduit<Object> get(InstanceContext context)
098            {
099                return new EnvironmentalConduit(componentClassName, fieldName, fieldType, required);
100            }
101
102            public void set(Object instance, InstanceContext context, Object newValue)
103            {
104                throw new RuntimeException(
105                        String.format("Field %s of component %s is read only.", fieldName, componentClassName));
106            }
107        };
108
109        field.setComputedConduit(provider);
110    }
111
112}