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    
015    package org.apache.tapestry5.internal.transform;
016    
017    import org.apache.tapestry5.annotations.Environmental;
018    import org.apache.tapestry5.internal.services.ComponentClassCache;
019    import org.apache.tapestry5.model.MutableComponentModel;
020    import org.apache.tapestry5.plastic.*;
021    import org.apache.tapestry5.services.Environment;
022    import org.apache.tapestry5.services.transform.ComponentClassTransformWorker2;
023    import 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")
030    public 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    }